[PATCH v2 0/5] gdb: introduce limited array lengths while printing values

[PATCH v2 0/5] gdb: introduce limited array lengths while printing values

[Maciej W. Rozycki]

Hi,

 This is v2 of Andrew's RFC, originally posted here: 
<https://sourceware.org/pipermail/gdb-patches/2021-October/182435.html>.

 Following Tom's feedback I have updated the original change so that data 
up to `max-value-size' is retrieved and stored in the history regardless 
of how much less has been requested with the relevant `print' command.  

 This has revealed issues with value history handling where entries were 
not retrieved due to `max-value-size' setting where accessing the original 
data object would work, and then where out of range accesses pretended to 
retrieve data or returned memory faults.

 I have updated the change to make the `output' command follow the same 
rules (except for storing the value retrieved in the value history of 
course).  This in turn required a test framework update as it seems the 
only command that does not produce a new line character/sequence between 
data output and the following command prompt; this has also revealed this 
command had no testsuite coverage at all until now.

 Consequently this has now become a patch series addressing each of these 
issues individually.  See individual change descriptions (and any extra 
discussion) for details.

 I have regression-tested it natively with a `x86_64-linux-gnu' system.  
OK to apply?

  Maciej

[PATCH v2 1/5] GDB: Ignore `max-value-size' setting with value history accesses

[Maciej W. Rozycki]

We have an inconsistency in value history accesses where array element 
accesses cause an error for entries exceeding the currently selected 
`max-value-size' setting even where such accesses successfully complete 
for elements located in the inferior, e.g.:

  (gdb) p/d one
  $1 = 0
  (gdb) p/d one_hundred
  $2 = {0 <repeats 100 times>}
  (gdb) p/d one_hundred[99]
  $3 = 0
  (gdb) set max-value-size 25
  (gdb) p/d one_hundred
  value requires 100 bytes, which is more than max-value-size
  (gdb) p/d one_hundred[99]
  $7 = 0
  (gdb) p/d $2
  value requires 100 bytes, which is more than max-value-size
  (gdb) p/d $2[99]
  value requires 100 bytes, which is more than max-value-size
  (gdb) 

According to our documentation the `max-value-size' setting is a safety 
guard against allocating an overly large amount of memory.  Moreover a 
statement in documentation says, concerning this setting, that: "Setting 
this variable does not effect values that have already been allocated 
within GDB, only future allocations."  While in the implementer-speak 
the sentence may be unambiguous I think the outside user may well infer 
that the setting only applies to values that need to be retrieved from 
the debuggee.

Therefore rather than just fixing this inconsistency it seems reasonable 
to lift the setting for value history accesses, under an implication 
that by having been retrieved from the debuggee they have already passed 
the safety check.  Do it then, making the last two commands succeed:

  (gdb) p/d $2
  $8 = {0 <repeats 100 times>}
  (gdb) p/d $2 [99]
  $9 = 0
  (gdb) 

Expand the testsuite accordingly.
---
 gdb/testsuite/gdb.base/max-value-size.exp |    3 +
 gdb/value.c                               |   56 ++++++++++++++++++++----------
 2 files changed, 42 insertions(+), 17 deletions(-)

gdb-value-history-size.diff
Index: src/gdb/testsuite/gdb.base/max-value-size.exp
===================================================================
--- src.orig/gdb/testsuite/gdb.base/max-value-size.exp
+++ src/gdb/testsuite/gdb.base/max-value-size.exp
@@ -53,6 +53,9 @@ proc do_value_printing { max_value_size
 	    gdb_test "p/d one_hundred" " = \\{0 <repeats 100 times>\\}"
 	}
 	gdb_test "p/d one_hundred \[99\]" " = 0"
+	# Verify that accessing value history is undisturbed.
+	gdb_test "p/d \$2" " = \\{0 <repeats 100 times>\\}"
+	gdb_test "p/d \$2 \[99\]" " = 0"
     }
 }
 
Index: src/gdb/value.c
===================================================================
--- src.orig/gdb/value.c
+++ src/gdb/value.c
@@ -1034,31 +1034,42 @@ check_type_length_before_alloc (const st
     }
 }
 
-/* Allocate the contents of VAL if it has not been allocated yet.  */
+/* Allocate the contents of VAL if it has not been allocated yet.
+   If CHECK_SIZE is true, then apply the usual max-value-size checks.  */
 
 static void
-allocate_value_contents (struct value *val)
+allocate_value_contents (struct value *val, bool check_size)
 {
   if (!val->contents)
     {
-      check_type_length_before_alloc (val->enclosing_type);
+      if (check_size)
+	check_type_length_before_alloc (val->enclosing_type);
       val->contents.reset
 	((gdb_byte *) xzalloc (val->enclosing_type->length ()));
     }
 }
 
-/* Allocate a  value  and its contents for type TYPE.  */
+/* Allocate a value and its contents for type TYPE.  If CHECK_SIZE is true,
+   then apply the usual max-value-size checks.  */
 
-struct value *
-allocate_value (struct type *type)
+static struct value *
+allocate_value (struct type *type, bool check_size)
 {
   struct value *val = allocate_value_lazy (type);
 
-  allocate_value_contents (val);
+  allocate_value_contents (val, check_size);
   val->lazy = 0;
   return val;
 }
 
+/* Allocate a value and its contents for type TYPE.  */
+
+struct value *
+allocate_value (struct type *type)
+{
+  return allocate_value (type, true);
+}
+
 /* Allocate a  value  that has the correct length
    for COUNT repetitions of type TYPE.  */
 
@@ -1169,7 +1180,7 @@ value_contents_raw (struct value *value)
   struct gdbarch *arch = get_value_arch (value);
   int unit_size = gdbarch_addressable_memory_unit_size (arch);
 
-  allocate_value_contents (value);
+  allocate_value_contents (value, true);
 
   ULONGEST length = value_type (value)->length ();
   return gdb::make_array_view
@@ -1179,7 +1190,7 @@ value_contents_raw (struct value *value)
 gdb::array_view<gdb_byte>
 value_contents_all_raw (struct value *value)
 {
-  allocate_value_contents (value);
+  allocate_value_contents (value, true);
 
   ULONGEST length = value_enclosing_type (value)->length ();
   return gdb::make_array_view (value->contents.get (), length);
@@ -1752,12 +1763,14 @@ value_release_to_mark (const struct valu
   return result;
 }
 
-/* Return a copy of the value ARG.
-   It contains the same contents, for same memory address,
-   but it's a different block of storage.  */
+/* Return a copy of the value ARG.  It contains the same contents,
+   for the same memory address, but it's a different block of storage.
+   If CHECK_SIZE is true, then throw an exception whenever the size
+   of memory allocated for the contents of the value would exceed
+   max-value-size.  */
 
-struct value *
-value_copy (const value *arg)
+static struct value *
+value_copy (const value *arg, bool check_size)
 {
   struct type *encl_type = value_enclosing_type (arg);
   struct value *val;
@@ -1765,7 +1778,7 @@ value_copy (const value *arg)
   if (value_lazy (arg))
     val = allocate_value_lazy (encl_type);
   else
-    val = allocate_value (encl_type);
+    val = allocate_value (encl_type, check_size);
   val->type = arg->type;
   VALUE_LVAL (val) = arg->lval;
   val->location = arg->location;
@@ -1802,6 +1815,15 @@ value_copy (const value *arg)
   return val;
 }
 
+/* Return a copy of the value ARG.  It contains the same contents,
+   for the same memory address, but it's a different block of storage.  */
+
+struct value *
+value_copy (const value *arg)
+{
+  return value_copy (arg, true);
+}
+
 /* Return a "const" and/or "volatile" qualified version of the value V.
    If CNST is true, then the returned value will be qualified with
    "const".
@@ -1965,7 +1987,7 @@ access_value_history (int num)
 
   absnum--;
 
-  return value_copy (value_history[absnum].get ());
+  return value_copy (value_history[absnum].get (), false);
 }
 
 /* See value.h.  */
@@ -4162,7 +4184,7 @@ void
 value_fetch_lazy (struct value *val)
 {
   gdb_assert (value_lazy (val));
-  allocate_value_contents (val);
+  allocate_value_contents (val, true);
   /* A value is either lazy, or fully fetched.  The
      availability/validity is only established as we try to fetch a
      value.  */

Re: [PATCH v2 1/5] GDB: Ignore `max-value-size' setting with value history accesses

[Andrew Burgess]

"Maciej W. Rozycki" <macro@embecosm.com> writes:

> We have an inconsistency in value history accesses where array element 
> accesses cause an error for entries exceeding the currently selected 
> `max-value-size' setting even where such accesses successfully complete 
> for elements located in the inferior, e.g.:
>
>   (gdb) p/d one
>   $1 = 0
>   (gdb) p/d one_hundred
>   $2 = {0 <repeats 100 times>}
>   (gdb) p/d one_hundred[99]
>   $3 = 0
>   (gdb) set max-value-size 25
>   (gdb) p/d one_hundred
>   value requires 100 bytes, which is more than max-value-size
>   (gdb) p/d one_hundred[99]
>   $7 = 0
>   (gdb) p/d $2
>   value requires 100 bytes, which is more than max-value-size
>   (gdb) p/d $2[99]
>   value requires 100 bytes, which is more than max-value-size
>   (gdb) 
>
> According to our documentation the `max-value-size' setting is a safety 
> guard against allocating an overly large amount of memory.  Moreover a 
> statement in documentation says, concerning this setting, that: "Setting 
> this variable does not effect values that have already been allocated 
> within GDB, only future allocations."  While in the implementer-speak 
> the sentence may be unambiguous I think the outside user may well infer 
> that the setting only applies to values that need to be retrieved from 
> the debuggee.
>
> Therefore rather than just fixing this inconsistency it seems reasonable 
> to lift the setting for value history accesses, under an implication 
> that by having been retrieved from the debuggee they have already passed 
> the safety check.  Do it then, making the last two commands succeed:
>
>   (gdb) p/d $2
>   $8 = {0 <repeats 100 times>}
>   (gdb) p/d $2 [99]
>   $9 = 0
>   (gdb) 
>
> Expand the testsuite accordingly.
> ---
>  gdb/testsuite/gdb.base/max-value-size.exp |    3 +
>  gdb/value.c                               |   56 ++++++++++++++++++++----------
>  2 files changed, 42 insertions(+), 17 deletions(-)
>
> gdb-value-history-size.diff
> Index: src/gdb/testsuite/gdb.base/max-value-size.exp
> ===================================================================
> --- src.orig/gdb/testsuite/gdb.base/max-value-size.exp
> +++ src/gdb/testsuite/gdb.base/max-value-size.exp
> @@ -53,6 +53,9 @@ proc do_value_printing { max_value_size
>  	    gdb_test "p/d one_hundred" " = \\{0 <repeats 100 times>\\}"
>  	}
>  	gdb_test "p/d one_hundred \[99\]" " = 0"
> +	# Verify that accessing value history is undisturbed.
> +	gdb_test "p/d \$2" " = \\{0 <repeats 100 times>\\}"
> +	gdb_test "p/d \$2 \[99\]" " = 0"
>      }
>  }
>  
> Index: src/gdb/value.c
> ===================================================================
> --- src.orig/gdb/value.c
> +++ src/gdb/value.c
> @@ -1034,31 +1034,42 @@ check_type_length_before_alloc (const st
>      }
>  }
>  
> -/* Allocate the contents of VAL if it has not been allocated yet.  */
> +/* Allocate the contents of VAL if it has not been allocated yet.
> +   If CHECK_SIZE is true, then apply the usual max-value-size checks.  */
>  
>  static void
> -allocate_value_contents (struct value *val)
> +allocate_value_contents (struct value *val, bool check_size)
>  {
>    if (!val->contents)
>      {
> -      check_type_length_before_alloc (val->enclosing_type);
> +      if (check_size)
> +	check_type_length_before_alloc (val->enclosing_type);
>        val->contents.reset
>  	((gdb_byte *) xzalloc (val->enclosing_type->length ()));
>      }
>  }
>  
> -/* Allocate a  value  and its contents for type TYPE.  */
> +/* Allocate a value and its contents for type TYPE.  If CHECK_SIZE is true,
> +   then apply the usual max-value-size checks.  */
>  
> -struct value *
> -allocate_value (struct type *type)
> +static struct value *
> +allocate_value (struct type *type, bool check_size)
>  {
>    struct value *val = allocate_value_lazy (type);
>  
> -  allocate_value_contents (val);
> +  allocate_value_contents (val, check_size);
>    val->lazy = 0;
>    return val;
>  }
>  
> +/* Allocate a value and its contents for type TYPE.  */
> +
> +struct value *
> +allocate_value (struct type *type)
> +{
> +  return allocate_value (type, true);
> +}
> +
>  /* Allocate a  value  that has the correct length
>     for COUNT repetitions of type TYPE.  */
>  
> @@ -1169,7 +1180,7 @@ value_contents_raw (struct value *value)
>    struct gdbarch *arch = get_value_arch (value);
>    int unit_size = gdbarch_addressable_memory_unit_size (arch);
>  
> -  allocate_value_contents (value);
> +  allocate_value_contents (value, true);
>  
>    ULONGEST length = value_type (value)->length ();
>    return gdb::make_array_view
> @@ -1179,7 +1190,7 @@ value_contents_raw (struct value *value)
>  gdb::array_view<gdb_byte>
>  value_contents_all_raw (struct value *value)
>  {
> -  allocate_value_contents (value);
> +  allocate_value_contents (value, true);
>  
>    ULONGEST length = value_enclosing_type (value)->length ();
>    return gdb::make_array_view (value->contents.get (), length);
> @@ -1752,12 +1763,14 @@ value_release_to_mark (const struct valu
>    return result;
>  }
>  
> -/* Return a copy of the value ARG.
> -   It contains the same contents, for same memory address,
> -   but it's a different block of storage.  */
> +/* Return a copy of the value ARG.  It contains the same contents,
> +   for the same memory address, but it's a different block of storage.
> +   If CHECK_SIZE is true, then throw an exception whenever the size
> +   of memory allocated for the contents of the value would exceed
> +   max-value-size.  */
>  
> -struct value *
> -value_copy (const value *arg)
> +static struct value *
> +value_copy (const value *arg, bool check_size)
>  {
>    struct type *encl_type = value_enclosing_type (arg);
>    struct value *val;
> @@ -1765,7 +1778,7 @@ value_copy (const value *arg)
>    if (value_lazy (arg))
>      val = allocate_value_lazy (encl_type);
>    else
> -    val = allocate_value (encl_type);
> +    val = allocate_value (encl_type, check_size);

I wonder, maybe value_copy should never check the max-value-size.  As
you point out above, the max-value-size was introduced to catch cases
where attempting to read a value from the inferior would cause GDB to
try an allocate a stupid amount of memory.

We don't currently have any mechanism in GDB to try an cap the
cumulative memory usage across all values, which suggests that
currently, once a value has been read into GDB we assume we can safely
make as many copies as we want.

And so, is there any reason why value_copy shouldn't always disable the
size check?

Thanks,
Andrew



>    val->type = arg->type;
>    VALUE_LVAL (val) = arg->lval;
>    val->location = arg->location;
> @@ -1802,6 +1815,15 @@ value_copy (const value *arg)
>    return val;
>  }
>  
> +/* Return a copy of the value ARG.  It contains the same contents,
> +   for the same memory address, but it's a different block of storage.  */
> +
> +struct value *
> +value_copy (const value *arg)
> +{
> +  return value_copy (arg, true);
> +}
> +
>  /* Return a "const" and/or "volatile" qualified version of the value V.
>     If CNST is true, then the returned value will be qualified with
>     "const".
> @@ -1965,7 +1987,7 @@ access_value_history (int num)
>  
>    absnum--;
>  
> -  return value_copy (value_history[absnum].get ());
> +  return value_copy (value_history[absnum].get (), false);
>  }
>  
>  /* See value.h.  */
> @@ -4162,7 +4184,7 @@ void
>  value_fetch_lazy (struct value *val)
>  {
>    gdb_assert (value_lazy (val));
> -  allocate_value_contents (val);
> +  allocate_value_contents (val, true);
>    /* A value is either lazy, or fully fetched.  The
>       availability/validity is only established as we try to fetch a
>       value.  */

Re: [PATCH v2 1/5] GDB: Ignore `max-value-size' setting with value history accesses

[Maciej W. Rozycki]

On Fri, 13 Jan 2023, Andrew Burgess wrote:

> > @@ -1752,12 +1763,14 @@ value_release_to_mark (const struct valu
> >    return result;
> >  }
> >  
> > -/* Return a copy of the value ARG.
> > -   It contains the same contents, for same memory address,
> > -   but it's a different block of storage.  */
> > +/* Return a copy of the value ARG.  It contains the same contents,
> > +   for the same memory address, but it's a different block of storage.
> > +   If CHECK_SIZE is true, then throw an exception whenever the size
> > +   of memory allocated for the contents of the value would exceed
> > +   max-value-size.  */
> >  
> > -struct value *
> > -value_copy (const value *arg)
> > +static struct value *
> > +value_copy (const value *arg, bool check_size)
> >  {
> >    struct type *encl_type = value_enclosing_type (arg);
> >    struct value *val;
> > @@ -1765,7 +1778,7 @@ value_copy (const value *arg)
> >    if (value_lazy (arg))
> >      val = allocate_value_lazy (encl_type);
> >    else
> > -    val = allocate_value (encl_type);
> > +    val = allocate_value (encl_type, check_size);
> 
> I wonder, maybe value_copy should never check the max-value-size.  As
> you point out above, the max-value-size was introduced to catch cases
> where attempting to read a value from the inferior would cause GDB to
> try an allocate a stupid amount of memory.
> 
> We don't currently have any mechanism in GDB to try an cap the
> cumulative memory usage across all values, which suggests that
> currently, once a value has been read into GDB we assume we can safely
> make as many copies as we want.
> 
> And so, is there any reason why value_copy shouldn't always disable the
> size check?

 I had to investigate that and found out that in addition to value history 
accesses `value_copy' is only used for internal variables (which is fine; 
I guess that's one reason for the minimum of 16 set for `max-value-size'), 
and then an obscure piece of code called `make_cv_value'.

 Said function is only referred to from Python and Scheme support code, 
and its interaction with `max-value-size' is not covered by the testsuite.  
I have added a suitable test case then and that has verified it is indeed 
fine for `value_copy' to always disable the size check.

 Thank you for the suggestion then.  Since I missed a couple of copyright 
year updates with the original submission and also Tom's recent conversion 
requires the use of `allow_ada_tests' rather than `skip_ada_tests' in Ada 
test cases, I'll respin the patch series with all the necessary updates.

  Maciej

[PATCH v2 2/5] GDB: Fix the mess with value byte/bit range types

[Maciej W. Rozycki]

Consistently use the LONGEST and ULONGEST types for value byte/bit 
offsets and lengths respectively, avoiding slient truncation for ranges 
exceeding the 32-bit span, which may cause incorrect matching.  Also 
report a conversion overflow on byte ranges that cannot be expressed in 
terms of bits with these data types, e.g.:

  (gdb) print one_hundred[1LL << 58]
  Integer overflow in data location calculation
  (gdb) print one_hundred[(-1LL << 58) - 1]
  Integer overflow in data location calculation
  (gdb)

Previously such accesses would be let through with unpredictable results 
produced.
---
 gdb/value.c |   43 ++++++++++++++++++++++++++-----------------
 gdb/value.h |    8 ++++----
 2 files changed, 30 insertions(+), 21 deletions(-)

gdb-value-range-types.diff
Index: src/gdb/value.c
===================================================================
--- src.orig/gdb/value.c
+++ src/gdb/value.c
@@ -74,7 +74,7 @@ struct range
   LONGEST offset;
 
   /* Length of the range.  */
-  LONGEST length;
+  ULONGEST length;
 
   /* Returns true if THIS is strictly less than OTHER, useful for
      searching.  We keep ranges sorted by offset and coalesce
@@ -97,10 +97,10 @@ struct range
    [offset2, offset2+len2) overlap.  */
 
 static int
-ranges_overlap (LONGEST offset1, LONGEST len1,
-		LONGEST offset2, LONGEST len2)
+ranges_overlap (LONGEST offset1, ULONGEST len1,
+		LONGEST offset2, ULONGEST len2)
 {
-  ULONGEST h, l;
+  LONGEST h, l;
 
   l = std::max (offset1, offset2);
   h = std::min (offset1 + len1, offset2 + len2);
@@ -112,7 +112,7 @@ ranges_overlap (LONGEST offset1, LONGEST
 
 static int
 ranges_contain (const std::vector<range> &ranges, LONGEST offset,
-		LONGEST length)
+		ULONGEST length)
 {
   range what;
 
@@ -380,7 +380,8 @@ get_value_arch (const struct value *valu
 }
 
 int
-value_bits_available (const struct value *value, LONGEST offset, LONGEST length)
+value_bits_available (const struct value *value,
+		      LONGEST offset, ULONGEST length)
 {
   gdb_assert (!value->lazy);
 
@@ -389,8 +390,16 @@ value_bits_available (const struct value
 
 int
 value_bytes_available (const struct value *value,
-		       LONGEST offset, LONGEST length)
+		       LONGEST offset, ULONGEST length)
 {
+  ULONGEST sign = (1ULL << (sizeof (ULONGEST) * 8 - 1)) / TARGET_CHAR_BIT;
+  ULONGEST mask = (sign << 1) - 1;
+
+  if (offset != ((offset & mask) ^ sign) - sign
+      || length != ((length & mask) ^ sign) - sign
+      || (length > 0 && (~offset & (offset + length - 1) & sign) != 0))
+    error (_("Integer overflow in data location calculation"));
+
   return value_bits_available (value,
 			       offset * TARGET_CHAR_BIT,
 			       length * TARGET_CHAR_BIT);
@@ -460,7 +469,7 @@ value_entirely_optimized_out (struct val
 
 static void
 insert_into_bit_range_vector (std::vector<range> *vectorp,
-			      LONGEST offset, LONGEST length)
+			      LONGEST offset, ULONGEST length)
 {
   range newr;
 
@@ -558,8 +567,8 @@ insert_into_bit_range_vector (std::vecto
       if (ranges_overlap (bef.offset, bef.length, offset, length))
 	{
 	  /* #1 */
-	  ULONGEST l = std::min (bef.offset, offset);
-	  ULONGEST h = std::max (bef.offset + bef.length, offset + length);
+	  LONGEST l = std::min (bef.offset, offset);
+	  LONGEST h = std::max (bef.offset + bef.length, offset + length);
 
 	  bef.offset = l;
 	  bef.length = h - l;
@@ -600,7 +609,7 @@ insert_into_bit_range_vector (std::vecto
 	  struct range &r = *i;
 	  if (r.offset <= t.offset + t.length)
 	    {
-	      ULONGEST l, h;
+	      LONGEST l, h;
 
 	      l = std::min (t.offset, r.offset);
 	      h = std::max (t.offset + t.length, r.offset + r.length);
@@ -626,14 +635,14 @@ insert_into_bit_range_vector (std::vecto
 
 void
 mark_value_bits_unavailable (struct value *value,
-			     LONGEST offset, LONGEST length)
+			     LONGEST offset, ULONGEST length)
 {
   insert_into_bit_range_vector (&value->unavailable, offset, length);
 }
 
 void
 mark_value_bytes_unavailable (struct value *value,
-			      LONGEST offset, LONGEST length)
+			      LONGEST offset, ULONGEST length)
 {
   mark_value_bits_unavailable (value,
 			       offset * TARGET_CHAR_BIT,
@@ -786,7 +795,7 @@ static int
 find_first_range_overlap_and_match (struct ranges_and_idx *rp1,
 				    struct ranges_and_idx *rp2,
 				    LONGEST offset1, LONGEST offset2,
-				    LONGEST length, ULONGEST *l, ULONGEST *h)
+				    ULONGEST length, ULONGEST *l, ULONGEST *h)
 {
   rp1->idx = find_first_range_overlap (rp1->ranges, rp1->idx,
 				       offset1, length);
@@ -1306,14 +1315,14 @@ value_contents_all (struct value *value)
 static void
 ranges_copy_adjusted (std::vector<range> *dst_range, int dst_bit_offset,
 		      const std::vector<range> &src_range, int src_bit_offset,
-		      int bit_length)
+		      unsigned int bit_length)
 {
   for (const range &r : src_range)
     {
-      ULONGEST h, l;
+      LONGEST h, l;
 
       l = std::max (r.offset, (LONGEST) src_bit_offset);
-      h = std::min (r.offset + r.length,
+      h = std::min ((LONGEST) (r.offset + r.length),
 		    (LONGEST) src_bit_offset + bit_length);
 
       if (l < h)
Index: src/gdb/value.h
===================================================================
--- src.orig/gdb/value.h
+++ src/gdb/value.h
@@ -512,7 +512,7 @@ extern int value_bits_synthetic_pointer
    byte is unavailable.  */
 
 extern int value_bytes_available (const struct value *value,
-				  LONGEST offset, LONGEST length);
+				  LONGEST offset, ULONGEST length);
 
 /* Given a value, determine whether the contents bits starting at
    OFFSET and extending for LENGTH bits are available.  This returns
@@ -520,7 +520,7 @@ extern int value_bytes_available (const
    bit is unavailable.  */
 
 extern int value_bits_available (const struct value *value,
-				 LONGEST offset, LONGEST length);
+				 LONGEST offset, ULONGEST length);
 
 /* Like value_bytes_available, but return false if any byte in the
    whole object is unavailable.  */
@@ -534,13 +534,13 @@ extern int value_entirely_unavailable (s
    LENGTH bytes as unavailable.  */
 
 extern void mark_value_bytes_unavailable (struct value *value,
-					  LONGEST offset, LONGEST length);
+					  LONGEST offset, ULONGEST length);
 
 /* Mark VALUE's content bits starting at OFFSET and extending for
    LENGTH bits as unavailable.  */
 
 extern void mark_value_bits_unavailable (struct value *value,
-					 LONGEST offset, LONGEST length);
+					 LONGEST offset, ULONGEST length);
 
 /* Compare LENGTH bytes of VAL1's contents starting at OFFSET1 with
    LENGTH bytes of VAL2's contents starting at OFFSET2.

[PATCH v2 3/5] GDB: Only make data actually retrieved into value history available

[Maciej W. Rozycki]

While it makes sense to allow accessing out-of-bounds elements in the 
debuggee and see whatever there might happen to be there in memory (we 
are a debugger and not a programming rules enforcement facility and we 
want to make people's life easier in chasing bugs), e.g.:

  (gdb) print one_hundred[-1]
  $1 = 0
  (gdb) print one_hundred[100]
  $2 = 0
  (gdb) 

we shouldn't really pretend that we have any meaningful data around 
values recorded in history (what these commands really retrieve are 
current debuggee memory contents outside the original data accessed, 
really confusing in my opinion).  Add code to mark data around values 
recorded in history unavailable then:

  (gdb) print one_hundred[-1]
  $1 = <unavailable>
  (gdb) print one_hundred[100]
  $2 = <unavailable>

Adjust `value_entirely_available' accordingly; also zero-length types 
need special handling in `value_entirely_covered_by_range_vector'.

Add a suitable test case, which also covers integer overflows in data 
location calculation.
---
Hi,

 While at it I noticed that while values recorded in the history are just 
as one would expect immutable, one can poke at the original data object 
data in history has originated from by writing to the value in the 
history, e.g.:

  (gdb) print -elements 3 -- one_hundred
  $1 = {0, 1, 2...}
  (gdb) print -elements 3 -- $1
  $2 = {0, 1, 2...}
  (gdb) set $1[0] = -1
  (gdb) print -elements 3 -- $1
  $3 = {0, 1, 2...}
  (gdb) print -elements 3 -- one_hundred
  $4 = {-1, 1, 2...}
  (gdb) 

This is undocumented and I find it surprising to say the least.  Shall I 
file a bug for this phenomenon?

 LONG_MIN is not used, but I have thought we can have it anyway for 
consistency and so that people do not try to invent local variants.

  Maciej
---
 gdb/defs.h                                           |    8 ++
 gdb/testsuite/gdb.base/value-history-unavailable.c   |   29 +++++++
 gdb/testsuite/gdb.base/value-history-unavailable.exp |   73 +++++++++++++++++++
 gdb/valarith.c                                       |   15 +++
 gdb/value.c                                          |   24 ++++--
 5 files changed, 144 insertions(+), 5 deletions(-)

gdb-value-history-unavailable.diff
Index: src/gdb/defs.h
===================================================================
--- src.orig/gdb/defs.h
+++ src/gdb/defs.h
@@ -469,6 +469,10 @@ enum val_prettyformat
 #define	LONG_MAX ((long)(ULONG_MAX >> 1))   /* 0x7FFFFFFF for 32-bits */
 #endif
 
+#if !defined (LONG_MIN)                     /* 0x80000000 for 32-bits */
+#define	LONG_MIN ((long) (~(long) 0 ^ LONG_MAX))
+#endif
+
 #if !defined (ULONGEST_MAX)
 #define	ULONGEST_MAX (~(ULONGEST)0)        /* 0xFFFFFFFFFFFFFFFF for 64-bits */
 #endif
@@ -477,6 +481,10 @@ enum val_prettyformat
 #define	LONGEST_MAX ((LONGEST)(ULONGEST_MAX >> 1))
 #endif
 
+#if !defined (LONGEST_MIN)                 /* 0x8000000000000000 for 64-bits */
+#define	LONGEST_MIN ((LONGEST) (~(LONGEST) 0 ^ LONGEST_MAX))
+#endif
+
 /* * Convert a LONGEST to an int.  This is used in contexts (e.g. number of
    arguments to a function, number in a value history, register number, etc.)
    where the value must not be larger than can fit in an int.  */
Index: src/gdb/testsuite/gdb.base/value-history-unavailable.c
===================================================================
--- /dev/null
+++ src/gdb/testsuite/gdb.base/value-history-unavailable.c
@@ -0,0 +1,29 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+struct
+{
+  unsigned char x[1024];
+  unsigned char a[1024];
+  unsigned char y[1024];
+} a = { {-1} };
+
+int
+main ()
+{
+  return 0;
+}
Index: src/gdb/testsuite/gdb.base/value-history-unavailable.exp
===================================================================
--- /dev/null
+++ src/gdb/testsuite/gdb.base/value-history-unavailable.exp
@@ -0,0 +1,73 @@
+# Copyright (C) 2022 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test GDB's value availability ranges.
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
+    return -1
+}
+
+if ![runto_main] then {
+    perror "couldn't run to breakpoint"
+    continue
+}
+
+set target_char_mask [get_valueof "/u" "a.x\[0]" "255" "get target char mask"]
+set target_char_bit 0
+for {set i $target_char_mask} {$i > 0} {set i [expr $i >> 1]} {
+    incr target_char_bit
+}
+set target_char_rank -1
+for {set i $target_char_bit} {$i > 0} {set i [expr $i >> 1]} {
+    incr target_char_rank
+}
+
+# Verify accesses to original inferior data.
+gdb_test "print a.a" "\\\$2 = '\\\\000' <repeats 1023 times>"
+gdb_test "print a.a\[-1\]" "\\\$3 = 0 '\\\\000'"
+gdb_test "print a.a\[1024\]" "\\\$4 = 0 '\\\\000'"
+
+# Verify in-range value history accesses.
+gdb_test "print \$2" "\\\$5 = '\\\\000' <repeats 1023 times>"
+gdb_test "print \$2\[0\]" "\\\$6 = 0 '\\\\000'"
+gdb_test "print \$2\[1023\]" "\\\$7 = 0 '\\\\000'"
+
+# Values outside the array recorded will have not been retrieved.
+gdb_test "print \$2\[-1\]" "\\\$8 = <unavailable>"
+gdb_test "print \$2\[1024\]" "\\\$9 = <unavailable>"
+gdb_test "print \$2\[-1LL << 63 - $target_char_rank\]" \
+	"\\\$10 = <unavailable>"
+gdb_test "print \$2\[(1LL << 63 - $target_char_rank) - 1\]" \
+	"\\\$11 = <unavailable>"
+
+# Accesses through pointers in history go straight to the inferior though.
+gdb_test "print \$2\[0\]@1" "\\\$12 = \"\""
+gdb_test "print \$2\[-1\]@1" "\\\$13 = \"\""
+gdb_test "print \$2\[1024\]@1" "\\\$14 = \"\""
+
+# Verify out-of-range value history accesses.
+gdb_test "print \$2\[(-1LL << 63 - $target_char_rank) - 1\]" \
+    "Integer overflow in data location calculation"
+gdb_test "print \$2\[(1LL << 63 - $target_char_rank)\]" \
+    "Integer overflow in data location calculation"
+gdb_test "print \$2\[-1LL << 63\]" \
+    "Integer overflow in data location calculation"
+gdb_test "print \$2\[(1ULL << 63) - 1\]" \
+    "Integer overflow in data location calculation"
+
+# Sanity-check a copy of an unavailable value.
+gdb_test "print \$11" "\\\$15 = <unavailable>"
Index: src/gdb/valarith.c
===================================================================
--- src.orig/gdb/valarith.c
+++ src/gdb/valarith.c
@@ -182,6 +182,21 @@ value_subscript (struct value *array, LO
 	}
 
       index -= *lowerbound;
+
+      /* Do not try to dereference a pointer to an unavailable value.
+	 Instead mock up a new one and give it the original address.  */
+      struct type *elt_type = check_typedef (tarray->target_type ());
+      LONGEST elt_size = type_length_units (elt_type);
+      if (!value_lazy (array)
+	  && !value_bytes_available (array, elt_size * index, elt_size))
+	{
+	  struct value *val = allocate_value (elt_type);
+	  mark_value_bytes_unavailable (val, 0, elt_size);
+	  VALUE_LVAL (val) = lval_memory;
+	  set_value_address (val, value_address (array) + elt_size * index);
+	  return val;
+	}
+
       array = value_coerce_array (array);
     }
 
Index: src/gdb/value.c
===================================================================
--- src.orig/gdb/value.c
+++ src/gdb/value.c
@@ -421,7 +421,9 @@ value_entirely_available (struct value *
   if (value->lazy)
     value_fetch_lazy (value);
 
-  if (value->unavailable.empty ())
+  if (value->unavailable.empty ()
+      || value_bytes_available (value, 0,
+				value_enclosing_type (value)->length ()))
     return 1;
   return 0;
 }
@@ -441,11 +443,12 @@ value_entirely_covered_by_range_vector (
 
   if (ranges.size () == 1)
     {
+      ULONGEST length = value_enclosing_type (value)->length ();
       const struct range &t = ranges[0];
 
-      if (t.offset == 0
-	  && t.length == (TARGET_CHAR_BIT
-			  * value_enclosing_type (value)->length ()))
+      if (length == 0)
+	return t.offset == 0 && t.length == 0;
+      if (t.offset <= 0 && t.offset + t.length >= TARGET_CHAR_BIT * length)
 	return 1;
     }
 
@@ -1277,7 +1280,9 @@ require_not_optimized_out (const struct
 static void
 require_available (const struct value *value)
 {
-  if (!value->unavailable.empty ())
+  if (!value->unavailable.empty ()
+      && !value_bytes_available (value, 0,
+				 value_enclosing_type (value)->length ()))
     throw_error (NOT_AVAILABLE_ERROR, _("value is not available"));
 }
 
@@ -1962,6 +1967,15 @@ record_latest_value (struct value *val)
      a value on the value history never changes.  */
   if (value_lazy (val))
     value_fetch_lazy (val);
+
+  /* Don't pretend we have anything available there in the history beyond
+     the boundaries of the value recorded.  It's not like inferior memory
+     where there is actual stuff underneath.  */
+  ULONGEST length = value_enclosing_type (val)->length ();
+  mark_value_bits_unavailable (val, LONGEST_MIN, 0 ^ LONGEST_MIN);
+  mark_value_bits_unavailable (val, length * TARGET_CHAR_BIT,
+			       LONGEST_MAX - length * TARGET_CHAR_BIT);
+
   /* We preserve VALUE_LVAL so that the user can find out where it was fetched
      from.  This is a bit dubious, because then *&$1 does not just return $1
      but the current contents of that location.  c'est la vie...  */

[PATCH v2 4/5] GDB/testsuite: Add `-nonl' option to `gdb_test'

[Maciej W. Rozycki]

Add a `-nonl' option to `gdb_test' making it possible to match output 
from commands such as `output' that do not produce a new line sequence 
at the end, e.g.:

  (gdb) output 0
  0(gdb)
---
 gdb/testsuite/lib/gdb.exp |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

gdb-test-nonl.diff
Index: src/gdb/testsuite/lib/gdb.exp
===================================================================
--- src.orig/gdb/testsuite/lib/gdb.exp
+++ src/gdb/testsuite/lib/gdb.exp
@@ -1395,6 +1395,8 @@ proc gdb_test_multiline { name args } {
 #   have any effect if -prompt is specified.
 # -lbl specifies that line-by-line matching will be used.
 # -nopass specifies that a PASS should not be issued.
+# -nonl specifies that no \r\n sequence is expected between PATTERN
+#   and the gdb prompt.
 #
 # Returns:
 #    1 if the test failed,
@@ -1410,6 +1412,7 @@ proc gdb_test { args } {
 	{no-prompt-anchor}
 	{lbl}
 	{nopass}
+	{nonl}
     }
 
     lassign $args command pattern message question response
@@ -1424,12 +1427,13 @@ proc gdb_test { args } {
     }
 
     set prompt [fill_in_default_prompt $prompt [expr !${no-prompt-anchor}]]
+    set nl [expr ${nonl} ? {""} : {"\[\r\n\]+"}]
 
     set saw_question 0
 
     set user_code {}
     lappend user_code {
-	-re "\[\r\n\]*(?:$pattern)\[\r\n\]+$prompt" {
+	-re "\[\r\n\]*(?:$pattern)$nl$prompt" {
 	    if { $question != "" & !$saw_question} {
 		fail $message
 	    } elseif {!$nopass} {

[PATCH v2 5/5] GDB: Introduce limited array lengths while printing values

[Maciej W. Rozycki]

From: Andrew Burgess <andrew.burgess@embecosm.com>

This commit introduces the idea of loading only part of an array in 
order to print it, what I call "limited length" arrays.

The motivation behind this work is to make it possible to print slices 
of very large arrays, where very large means bigger than 
`max-value-size'.

Consider this GDB session with the current GDB:

  (gdb) set max-value-size 100
  (gdb) p large_1d_array
  value requires 400 bytes, which is more than max-value-size
  (gdb) p -elements 10 -- large_1d_array
  value requires 400 bytes, which is more than max-value-size

notice that the request to print 10 elements still fails, even though 10 
elements should be less than the max-value-size.  With a patched version 
of GDB:

  (gdb) p -elements 10 -- large_1d_array
  $1 = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9...}

So now the print has succeeded.  It also has loaded `max-value-size' 
worth of data into value history, so the recorded value can be accessed 
consistently:

  (gdb) p -elements 10 -- $1
  $2 = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9...}
  (gdb) p $1
  $3 = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
    20, 21, 22, 23, 24, <unavailable> <repeats 75 times>}
  (gdb)

Accesses with other languages work similarly, although for Ada only 
C-style [] array element/dimension accesses use history.  For both Ada 
and Fortran () array element/dimension accesses go straight to the 
inferior, bypassing the value history just as with C pointers.

Co-Authored-By: Maciej W. Rozycki <macro@embecosm.com>
---
Changes from v1:

- Load `max-value-size' worth data into the value history for limited 
  length accesses and mark the area beyond unavailable.

- Handle the `output' command.

- Expand test coverage.
---
 gdb/NEWS                                     |    6 
 gdb/doc/gdb.texinfo                          |    9 
 gdb/f-valprint.c                             |   32 ++-
 gdb/printcmd.c                               |   16 +
 gdb/testsuite/gdb.ada/limited-length.exp     |  266 +++++++++++++++++++++++++++
 gdb/testsuite/gdb.ada/limited-length/foo.adb |   37 +++
 gdb/testsuite/gdb.ada/limited-length/pck.adb |   25 ++
 gdb/testsuite/gdb.ada/limited-length/pck.ads |   21 ++
 gdb/testsuite/gdb.base/limited-length.c      |   48 ++++
 gdb/testsuite/gdb.base/limited-length.exp    |  242 ++++++++++++++++++++++++
 gdb/testsuite/gdb.fortran/limited-length.exp |  222 ++++++++++++++++++++++
 gdb/testsuite/gdb.fortran/limited-length.f90 |   39 +++
 gdb/valprint.c                               |   10 -
 gdb/value.c                                  |  201 ++++++++++++++++++--
 gdb/value.h                                  |   17 +
 15 files changed, 1165 insertions(+), 26 deletions(-)
 create mode 100644 gdb/testsuite/gdb.ada/limited-length.exp
 create mode 100644 gdb/testsuite/gdb.ada/limited-length/foo.adb
 create mode 100644 gdb/testsuite/gdb.ada/limited-length/pck.adb
 create mode 100644 gdb/testsuite/gdb.ada/limited-length/pck.ads
 create mode 100644 gdb/testsuite/gdb.base/limited-length.c
 create mode 100644 gdb/testsuite/gdb.base/limited-length.exp
 create mode 100644 gdb/testsuite/gdb.fortran/limited-length.exp
 create mode 100644 gdb/testsuite/gdb.fortran/limited-length.f90

gdb-aburgess-limited-length-array.diff
Index: src/gdb/NEWS
===================================================================
--- src.orig/gdb/NEWS
+++ src/gdb/NEWS
@@ -354,6 +354,12 @@ GDB now supports floating-point on Loong
   Disabling this can cause a performance penalty when there are a lot of
   symbols to load, but is useful for debugging purposes.
 
+* The 'set print elements' setting now helps when printing large arrays.
+  If an array would otherwise exceed max-value-size, but 'print elements'
+  is set such that the number of elements to print is less than or equal
+  to 'max-value-size', GDB will now still print the array, however only
+  'max-value-size' worth of data will be added into the value history.
+
 * New commands
 
 maint set backtrace-on-fatal-signal on|off
Index: src/gdb/doc/gdb.texinfo
===================================================================
--- src.orig/gdb/doc/gdb.texinfo
+++ src/gdb/doc/gdb.texinfo
@@ -11756,6 +11756,14 @@ When @value{GDBN} starts, this limit is
 Setting @var{number-of-elements} to @code{unlimited} or zero means
 that the number of elements to print is unlimited.
 
+When printing very large arrays, whose size is greater than
+@code{max-value-size} (@pxref{set max-value-size,,max-value-size}),
+if the @code{print elements} is set such that the size of the elements
+being printed is less than or equal to @code{max-value-size}, then
+@value{GDBN} will print the array (up to the @code{print elements} limit),
+and only @code{max-value-size} worth of data will be added into the value
+history (@pxref{Value History, ,Value History}).
+
 @item show print elements
 Display the number of elements of a large array that @value{GDBN} will print.
 
@@ -14171,6 +14179,7 @@ may indicate a value that is incorrectly
 @value{GDBN} to try and allocate an overly large amount of memory.
 
 @table @code
+@anchor{set max-value-size}
 @kindex set max-value-size
 @item set max-value-size @var{bytes}
 @itemx set max-value-size unlimited
Index: src/gdb/f-valprint.c
===================================================================
--- src.orig/gdb/f-valprint.c
+++ src/gdb/f-valprint.c
@@ -261,10 +261,20 @@ class fortran_array_printer_impl : publi
     size_t dim_indx = m_dimension - 1;
     struct type *elt_type_prev = m_elt_type_prev;
     LONGEST elt_off_prev = m_elt_off_prev;
-    bool repeated = (m_options->repeat_count_threshold < UINT_MAX
-		     && elt_type_prev != nullptr
-		     && value_contents_eq (m_val, elt_off_prev, m_val, elt_off,
-					   elt_type->length ()));
+    bool repeated = false;
+
+    if (m_options->repeat_count_threshold < UINT_MAX
+	&& elt_type_prev != nullptr)
+      {
+	struct value *e_val = value_from_component (m_val, elt_type, elt_off);
+	struct value *e_prev = value_from_component (m_val, elt_type,
+						     elt_off_prev);
+	repeated = ((value_entirely_available (e_prev)
+		     && value_entirely_available (e_val)
+		     && value_contents_eq (e_prev, e_val))
+		    || (value_entirely_unavailable (e_prev)
+			&& value_entirely_unavailable (e_val)));
+      }
 
     if (repeated)
       m_nrepeats++;
@@ -333,7 +343,7 @@ class fortran_array_printer_impl : publi
      have been sliced and we do not want to compare any memory contents
      present between the slices requested.  */
   bool
-  dimension_contents_eq (const struct value *val, struct type *type,
+  dimension_contents_eq (struct value *val, struct type *type,
 			 LONGEST offset1, LONGEST offset2)
   {
     if (type->code () == TYPE_CODE_ARRAY
@@ -362,8 +372,16 @@ class fortran_array_printer_impl : publi
 	return true;
       }
     else
-      return value_contents_eq (val, offset1, val, offset2,
-				type->length ());
+      {
+	struct value *e_val1 = value_from_component (val, type, offset1);
+	struct value *e_val2 = value_from_component (val, type, offset2);
+
+	return ((value_entirely_available (e_val1)
+		 && value_entirely_available (e_val2)
+		 && value_contents_eq (e_val1, e_val2))
+		|| (value_entirely_unavailable (e_val1)
+		    && value_entirely_unavailable (e_val2)));
+      }
   }
 
   /* The number of elements printed so far.  */
Index: src/gdb/printcmd.c
===================================================================
--- src.orig/gdb/printcmd.c
+++ src/gdb/printcmd.c
@@ -1242,6 +1242,11 @@ print_command_parse_format (const char *
 void
 print_value (value *val, const value_print_options &opts)
 {
+  /* This setting allows large arrays to be printed by limiting the
+     number of elements that are loaded into GDB's memory; we only
+     need to load as many array elements as we plan to print.  */
+  scoped_array_length_limiting limit_large_arrays (opts.print_max);
+
   int histindex = record_latest_value (val);
 
   annotate_value_history_begin (histindex, value_type (val));
@@ -1301,6 +1306,11 @@ process_print_command_args (const char *
 
   if (exp != nullptr && *exp)
     {
+      /* This setting allows large arrays to be printed by limiting the
+	 number of elements that are loaded into GDB's memory; we only
+	 need to load as many array elements as we plan to print.  */
+      scoped_array_length_limiting limit_large_arrays (print_opts->print_max);
+
       /* VOIDPRINT is true to indicate that we do want to print a void
 	 value, so invert it for parse_expression.  */
       expression_up expr = parse_expression (exp, nullptr, !voidprint);
@@ -1489,6 +1499,12 @@ output_command (const char *exp, int fro
 
   get_formatted_print_options (&opts, format);
   opts.raw = fmt.raw;
+
+  /* This setting allows large arrays to be printed by limiting the
+     number of elements that are loaded into GDB's memory; we only
+     need to load as many array elements as we plan to print.  */
+  scoped_array_length_limiting limit_large_arrays (opts.print_max);
+
   print_formatted (val, fmt.size, &opts, gdb_stdout);
 
   annotate_value_end ();
Index: src/gdb/testsuite/gdb.ada/limited-length.exp
===================================================================
--- /dev/null
+++ src/gdb/testsuite/gdb.ada/limited-length.exp
@@ -0,0 +1,266 @@
+# Copyright 2023 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+load_lib "ada.exp"
+
+if {[skip_ada_tests]} {
+    return -1
+}
+
+standard_ada_testfile foo
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable \
+	[list debug ]] != "" } {
+  return -1
+}
+
+clean_restart ${testfile}
+
+set bp_location [gdb_get_line_number "STOP" ${testdir}/foo.adb]
+if {![runto "foo.adb:$bp_location"]} {
+    perror "Couldn't run ${testfile}"
+    return
+}
+
+with_test_prefix "with standard max-value size" {
+    gdb_test "print Large_1d_Array" \
+	" = \\(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,\
+	       13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,\
+	       25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,\
+	       37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,\
+	       49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60,\
+	       61, 62, 63, 64\\)"
+    gdb_test -nonl "output Large_1d_Array" \
+	"\\(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,\
+	    13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,\
+	    25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,\
+	    37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,\
+	    49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60,\
+	    61, 62, 63, 64\\)"
+    gdb_test "print Large_3d_Array" \
+	" = \\(\\(\\(1, 2, 3, 4\\), \\(5, 6, 7, 8\\),\
+		  \\(9, 10, 11, 12\\), \\(13, 14, 15, 16\\)\\),\
+	       \\(\\(17, 18, 19, 20\\), \\(21, 22, 23, 24\\),\
+		  \\(25, 26, 27, 28\\), \\(29, 30, 31, 32\\)\\),\
+	       \\(\\(33, 34, 35, 36\\), \\(37, 38, 39, 40\\),\
+		  \\(41, 42, 43, 44\\), \\(45, 46, 47, 48\\)\\),\
+	       \\(\\(49, 50, 51, 52\\), \\(53, 54, 55, 56\\),\
+		  \\(57, 58, 59, 60\\), \\(61, 62, 63, 64\\)\\)\\)"
+    gdb_test -nonl "output Large_3d_Array" \
+	"\\(\\(\\(1, 2, 3, 4\\), \\(5, 6, 7, 8\\),\
+	       \\(9, 10, 11, 12\\), \\(13, 14, 15, 16\\)\\),\
+	    \\(\\(17, 18, 19, 20\\), \\(21, 22, 23, 24\\),\
+	       \\(25, 26, 27, 28\\), \\(29, 30, 31, 32\\)\\),\
+	    \\(\\(33, 34, 35, 36\\), \\(37, 38, 39, 40\\),\
+	       \\(41, 42, 43, 44\\), \\(45, 46, 47, 48\\)\\),\
+	    \\(\\(49, 50, 51, 52\\), \\(53, 54, 55, 56\\),\
+	       \\(57, 58, 59, 60\\), \\(61, 62, 63, 64\\)\\)\\)"
+}
+
+# Set the max-value-size so we can only print 33 elements.
+set elements 33
+set elem_size [get_valueof "/d" "(Large_1d_Array(1)'Size + 7) / 8" "*unknown*"]
+gdb_test_no_output "set max-value-size [expr $elem_size * $elements]"
+
+with_test_prefix "with reduced max-value size" {
+    gdb_test "print Large_1d_Array" \
+	"value of type `.*' requires $decimal bytes,\
+	 which is more than max-value-size"
+    gdb_test "output Large_1d_Array" \
+	"value of type `.*' requires $decimal bytes,\
+	 which is more than max-value-size"
+    gdb_test "print Large_3d_Array" \
+	"value of type `.*' requires $decimal bytes,\
+	 which is more than max-value-size"
+    gdb_test "output Large_3d_Array" \
+	"value of type `.*' requires $decimal bytes,\
+	 which is more than max-value-size"
+}
+
+with_test_prefix "with reduced print -elements flag" {
+    gdb_test "print -elements 2 -- Large_1d_Array" \
+	" = \\(1, 2\\.\\.\\.\\)"
+    gdb_test "print -elements 2 -- Large_3d_Array" \
+	" = \\(\\(\\(1, 2\\.\\.\\.\\), \\(5, 6\\.\\.\\.\\)\\.\\.\\.\\),\
+	       \\(\\(17, 18\\.\\.\\.\\),\
+		  \\(21, 22\\.\\.\\.\\)\\.\\.\\.\\)\\.\\.\\.\\)"
+}
+
+gdb_test_no_output "set print elements 2"
+
+with_test_prefix "with reduced print elements" {
+    gdb_test "print Large_1d_Array" \
+	" = \\(1, 2\\.\\.\\.\\)"
+    gdb_test -nonl "output Large_1d_Array" \
+	"\\(1, 2\\.\\.\\.\\)"
+
+    gdb_test "print \$" \
+	" = \\(1, 2\\.\\.\\.\\)" \
+	"print Large_1d_Array from history"
+    gdb_test -nonl "output \$\$" \
+	"\\(1, 2\\.\\.\\.\\)" \
+	"output Large_1d_Array from history"
+
+    gdb_test "print Large_3d_Array" \
+	" = \\(\\(\\(1, 2\\.\\.\\.\\), \\(5, 6\\.\\.\\.\\)\\.\\.\\.\\),\
+	       \\(\\(17, 18\\.\\.\\.\\),\
+		  \\(21, 22\\.\\.\\.\\)\\.\\.\\.\\)\\.\\.\\.\\)"
+    gdb_test -nonl "output Large_3d_Array" \
+	"\\(\\(\\(1, 2\\.\\.\\.\\), \\(5, 6\\.\\.\\.\\)\\.\\.\\.\\),\
+	    \\(\\(17, 18\\.\\.\\.\\),\
+	       \\(21, 22\\.\\.\\.\\)\\.\\.\\.\\)\\.\\.\\.\\)"
+
+    gdb_test "print \$" \
+	" = \\(\\(\\(1, 2\\.\\.\\.\\), \\(5, 6\\.\\.\\.\\)\\.\\.\\.\\),\
+	       \\(\\(17, 18\\.\\.\\.\\),\
+		  \\(21, 22\\.\\.\\.\\)\\.\\.\\.\\)\\.\\.\\.\\)" \
+	"print Large_3d_Array from history"
+    gdb_test -nonl "output \$\$" \
+	"\\(\\(\\(1, 2\\.\\.\\.\\), \\(5, 6\\.\\.\\.\\)\\.\\.\\.\\),\
+	    \\(\\(17, 18\\.\\.\\.\\),\
+	       \\(21, 22\\.\\.\\.\\)\\.\\.\\.\\)\\.\\.\\.\\)" \
+	"output Large_3d_Array from history"
+}
+
+gdb_test_no_output "set print elements $elements"
+
+with_test_prefix "with print elements matching max-value size" {
+    gdb_test "print \$\$2" \
+	" = \\(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,\
+	       13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,\
+	       25, 26, 27, 28, 29, 30, 31, 32, 33\\.\\.\\.\\)" \
+	"print Large_1d_Array from history"
+    gdb_test -nonl "output \$\$3" \
+	"\\(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,\
+	    13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,\
+	    25, 26, 27, 28, 29, 30, 31, 32, 33\\.\\.\\.\\)" \
+	"output Large_1d_Array from history"
+
+    gdb_test "print \$\$2" \
+	" = \\(\\(\\(1, 2, 3, 4\\), \\(5, 6, 7, 8\\),\
+		  \\(9, 10, 11, 12\\), \\(13, 14, 15, 16\\)\\),\
+	       \\(\\(17, 18, 19, 20\\), \\(21, 22, 23, 24\\),\
+		  \\(25, 26, 27, 28\\), \\(29, 30, 31, 32\\)\\),\
+	       \\(\\(33(?:, <unavailable>)\{3\}\\)(?:,\
+		  \\(<unavailable>(?:, <unavailable>)\{3\}\\))\{3\}\\),\
+	       \\(\\(<unavailable>(?:, <unavailable>)\{3\}\\)(?:,\
+		  \\(<unavailable>(?:, <unavailable>)\{3\}\\))\{3\}\\)\\)" \
+	"print Large_3d_Array from history"
+    gdb_test -nonl "output \$\$3" \
+        "\\(\\(\\(1, 2, 3, 4\\), \\(5, 6, 7, 8\\),\
+	       \\(9, 10, 11, 12\\), \\(13, 14, 15, 16\\)\\),\
+	    \\(\\(17, 18, 19, 20\\), \\(21, 22, 23, 24\\),\
+	       \\(25, 26, 27, 28\\), \\(29, 30, 31, 32\\)\\),\
+	    \\(\\(33(?:, <unavailable>)\{3\}\\)(?:,\
+	       \\(<unavailable>(?:, <unavailable>)\{3\}\\))\{3\}\\),\
+	    \\(\\(<unavailable>(?:, <unavailable>)\{3\}\\)(?:,\
+	       \\(<unavailable>(?:, <unavailable>)\{3\}\\))\{3\}\\)\\)" \
+	"output Large_3d_Array from history"
+}
+
+gdb_test_no_output "set max-value-size unlimited"
+gdb_test_no_output "set print elements unlimited"
+gdb_test_no_output "set print repeats 2"
+
+with_test_prefix "with unlimited print elements" {
+    gdb_test "print \$\$" \
+	" = \\(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,\
+	       13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,\
+	       25, 26, 27, 28, 29, 30, 31, 32, 33,\
+	       <unavailable> <repeats 31 times>\\)" \
+	"print Large_1d_Array from history"
+    gdb_test -nonl "output \$\$2" \
+	"\\(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,\
+	    13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,\
+	    25, 26, 27, 28, 29, 30, 31, 32, 33,\
+	    <unavailable> <repeats 31 times>\\)" \
+	"output Large_1d_Array from history"
+
+    gdb_test "print \$\$" \
+	" = \\(\\(\\(1, 2, 3, 4\\), \\(5, 6, 7, 8\\),\
+		  \\(9, 10, 11, 12\\), \\(13, 14, 15, 16\\)\\),\
+	       \\(\\(17, 18, 19, 20\\), \\(21, 22, 23, 24\\),\
+		  \\(25, 26, 27, 28\\), \\(29, 30, 31, 32\\)\\),\
+	       \\(\\(33, <unavailable> <repeats 3 times>\\),\
+		  \\(<unavailable> <repeats 4 times>\\) <repeats 3 times>\\),\
+	       \\(\\(<unavailable> <repeats 4 times>\\)\
+		  <repeats 4 times>\\)\\)" \
+	"print Large_3d_Array from history"
+    gdb_test -nonl "output \$\$2" \
+	"\\(\\(\\(1, 2, 3, 4\\), \\(5, 6, 7, 8\\),\
+	       \\(9, 10, 11, 12\\), \\(13, 14, 15, 16\\)\\),\
+	    \\(\\(17, 18, 19, 20\\), \\(21, 22, 23, 24\\),\
+	       \\(25, 26, 27, 28\\), \\(29, 30, 31, 32\\)\\),\
+	    \\(\\(33, <unavailable> <repeats 3 times>\\),\
+	       \\(<unavailable> <repeats 4 times>\\) <repeats 3 times>\\),\
+	    \\(\\(<unavailable> <repeats 4 times>\\) <repeats 4 times>\\)\\)" \
+	"output Large_3d_Array from history"
+
+    gdb_test "print \$\[2\]" \
+	" = \\(\\(17, 18, 19, 20\\), \\(21, 22, 23, 24\\),\
+	       \\(25, 26, 27, 28\\), \\(29, 30, 31, 32\\)\\)" \
+	"print available Large_3d_Array row from history"
+    gdb_test -nonl "output \$\$\[2\]" \
+	"\\(\\(17, 18, 19, 20\\), \\(21, 22, 23, 24\\),\
+	    \\(25, 26, 27, 28\\), \\(29, 30, 31, 32\\)\\)" \
+	"output available Large_3d_Array row from history"
+
+    gdb_test "print \$\$\[3\]" \
+	" = \\(\\(33, <unavailable> <repeats 3 times>\\),\
+               \\(<unavailable> <repeats 4 times>\\) <repeats 3 times>\\)" \
+	"print partially available Large_3d_Array row from history"
+    gdb_test -nonl "output \$\$2\[3\]" \
+	"\\(\\(33, <unavailable> <repeats 3 times>\\),\
+            \\(<unavailable> <repeats 4 times>\\) <repeats 3 times>\\)" \
+	"output partially available Large_3d_Array row from history"
+
+    # These go straigth to the inferior.
+    gdb_test "print \$\$2(3)" \
+	" = \\(\\(33, 34, 35, 36\\), \\(37, 38, 39, 40\\),\
+	       \\(41, 42, 43, 44\\), \\(45, 46, 47, 48\\)\\)" \
+	"print partially available Large_3d_Array row bypassing history"
+    gdb_test -nonl "output \$\$3(3)" \
+	"\\(\\(33, 34, 35, 36\\), \\(37, 38, 39, 40\\),\
+	    \\(41, 42, 43, 44\\), \\(45, 46, 47, 48\\)\\)" \
+	"output partially available Large_3d_Array row bypassing history"
+
+    gdb_test "print \$\$3\[4\]" \
+	" = <unavailable>" \
+	"print unavailable Large_3d_Array row from history"
+    gdb_test -nonl "output \$\$4\[4\]" \
+	"<unavailable>" \
+	"output unavailable Large_3d_Array row from history"
+
+    gdb_test "print \$\$4\[3\]\[1\]\[1\]" \
+	" = 33" \
+	"print available Large_3d_Array element from history"
+    gdb_test -nonl "output \$\$5\[3\]\[1\]\[1\]" \
+	"33" \
+	"output available Large_3d_Array element from history"
+
+    gdb_test "print \$\$5\[3\]\[1\]\[2\]" \
+	" = <unavailable>" \
+	"print unavailable Large_3d_Array element from history"
+    gdb_test -nonl "output \$\$6\[3\]\[1\]\[2\]" \
+	"<unavailable>" \
+	"output unavailable Large_3d_Array element from history"
+
+    gdb_test "print \$\$6\[3\]\[1\]\[1\] + \$\$6\[3\]\[1\]\[2\]" \
+	"value is not available" \
+	"print expression referring unavailable element from history"
+    gdb_test "output \$\$6\[3\]\[1\]\[1\] + \$\$6\[3\]\[1\]\[2\]" \
+	"value is not available" \
+	"output expression referring unavailable element from history"
+}
Index: src/gdb/testsuite/gdb.ada/limited-length/foo.adb
===================================================================
--- /dev/null
+++ src/gdb/testsuite/gdb.ada/limited-length/foo.adb
@@ -0,0 +1,37 @@
+--  This testcase is part of GDB, the GNU debugger.
+--
+--  Copyright 2023 Free Software Foundation, Inc.
+--
+--  This program is free software; you can redistribute it and/or modify
+--  it under the terms of the GNU General Public License as published by
+--  the Free Software Foundation; either version 3 of the License, or
+--  (at your option) any later version.
+--
+--  This program is distributed in the hope that it will be useful,
+--  but WITHOUT ANY WARRANTY; without even the implied warranty of
+--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+--  GNU General Public License for more details.
+--
+--  You should have received a copy of the GNU General Public License
+--  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+with Pck; use Pck;
+
+procedure Foo is
+   Large_1d_Array : array (1..64) of Integer;
+   Large_3d_Array : array (1..4,1..4,1..4) of Integer;
+   Count : Integer := 1;
+begin
+   for i in 1 .. 4 loop
+     for j in 1 .. 4 loop
+        for k in 1 .. 4 loop
+           Large_1d_Array (Count) := Count;
+           Large_3d_Array (i,j,k) := Count;
+           Count := Count + 1;
+        end loop;
+     end loop;
+   end loop;
+   Do_Nothing (Large_1d_Array'Address);
+   Do_Nothing (Large_3d_Array'Address); -- STOP
+end Foo;
+
Index: src/gdb/testsuite/gdb.ada/limited-length/pck.adb
===================================================================
--- /dev/null
+++ src/gdb/testsuite/gdb.ada/limited-length/pck.adb
@@ -0,0 +1,25 @@
+--  This testcase is part of GDB, the GNU debugger.
+--
+--  Copyright 2023 Free Software Foundation, Inc.
+--
+--  This program is free software; you can redistribute it and/or modify
+--  it under the terms of the GNU General Public License as published by
+--  the Free Software Foundation; either version 3 of the License, or
+--  (at your option) any later version.
+--
+--  This program is distributed in the hope that it will be useful,
+--  but WITHOUT ANY WARRANTY; without even the implied warranty of
+--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+--  GNU General Public License for more details.
+--
+--  You should have received a copy of the GNU General Public License
+--  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package body Pck is
+
+   procedure Do_Nothing (A : System.Address) is
+   begin
+      null;
+   end Do_Nothing;
+
+end Pck;
Index: src/gdb/testsuite/gdb.ada/limited-length/pck.ads
===================================================================
--- /dev/null
+++ src/gdb/testsuite/gdb.ada/limited-length/pck.ads
@@ -0,0 +1,21 @@
+--  This testcase is part of GDB, the GNU debugger.
+--
+--  Copyright 2023 Free Software Foundation, Inc.
+--
+--  This program is free software; you can redistribute it and/or modify
+--  it under the terms of the GNU General Public License as published by
+--  the Free Software Foundation; either version 3 of the License, or
+--  (at your option) any later version.
+--
+--  This program is distributed in the hope that it will be useful,
+--  but WITHOUT ANY WARRANTY; without even the implied warranty of
+--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+--  GNU General Public License for more details.
+--
+--  You should have received a copy of the GNU General Public License
+--  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+with System;
+package Pck is
+   procedure Do_Nothing (A : System.Address);
+end Pck;
Index: src/gdb/testsuite/gdb.base/limited-length.c
===================================================================
--- /dev/null
+++ src/gdb/testsuite/gdb.base/limited-length.c
@@ -0,0 +1,48 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+int large_1d_array[] = {
+  0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
+  10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
+  20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
+  30, 31, 32, 33, 34, 35, 36, 37, 38, 39,
+  40, 41, 42, 43, 44, 45, 46, 47, 48, 49,
+  50, 51, 52, 53, 54, 55, 56, 57, 58, 59,
+  60, 61, 62, 63, 64, 65, 66, 67, 68, 69,
+  70, 71, 72, 73, 74, 75, 76, 77, 78, 79,
+  80, 81, 82, 83, 84, 85, 86, 87, 88, 89,
+  90, 91, 92, 93, 94, 95, 96, 97, 98, 99
+};
+
+int large_2d_array[][10] = {
+  {0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
+  {10, 11, 12, 13, 14, 15, 16, 17, 18, 19},
+  {20, 21, 22, 23, 24, 25, 26, 27, 28, 29},
+  {30, 31, 32, 33, 34, 35, 36, 37, 38, 39},
+  {40, 41, 42, 43, 44, 45, 46, 47, 48, 49},
+  {50, 51, 52, 53, 54, 55, 56, 57, 58, 59},
+  {60, 61, 62, 63, 64, 65, 66, 67, 68, 69},
+  {70, 71, 72, 73, 74, 75, 76, 77, 78, 79},
+  {80, 81, 82, 83, 84, 85, 86, 87, 88, 89},
+  {90, 91, 92, 93, 94, 95, 96, 97, 98, 99}
+};
+
+int
+main ()
+{
+  return 0;
+}
Index: src/gdb/testsuite/gdb.base/limited-length.exp
===================================================================
--- /dev/null
+++ src/gdb/testsuite/gdb.base/limited-length.exp
@@ -0,0 +1,242 @@
+# Copyright 2023 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test GDB's limited array printing.
+
+standard_testfile
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile]} {
+    return -1
+}
+
+if {![runto_main]} {
+    perror "couldn't run to breakpoint"
+    continue
+}
+
+with_test_prefix "with standard max-value size" {
+    gdb_test "print large_1d_array" \
+	" = \\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,\
+		12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,\
+		24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,\
+		36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,\
+		48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59,\
+		60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71,\
+		72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83,\
+		84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95,\
+		96, 97, 98, 99\\\}"
+    gdb_test -nonl "output large_1d_array" \
+	"\\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,\
+	     12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,\
+	     24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,\
+	     36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,\
+	     48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59,\
+	     60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71,\
+	     72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83,\
+	     84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95,\
+	     96, 97, 98, 99\\\}"
+    gdb_test "print large_2d_array" \
+	" = \\\{\\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9\\\},\
+		\\\{10, 11, 12, 13, 14, 15, 16, 17, 18, 19\\\},\
+		\\\{20, 21, 22, 23, 24, 25, 26, 27, 28, 29\\\},\
+		\\\{30, 31, 32, 33, 34, 35, 36, 37, 38, 39\\\},\
+		\\\{40, 41, 42, 43, 44, 45, 46, 47, 48, 49\\\},\
+		\\\{50, 51, 52, 53, 54, 55, 56, 57, 58, 59\\\},\
+		\\\{60, 61, 62, 63, 64, 65, 66, 67, 68, 69\\\},\
+		\\\{70, 71, 72, 73, 74, 75, 76, 77, 78, 79\\\},\
+		\\\{80, 81, 82, 83, 84, 85, 86, 87, 88, 89\\\},\
+		\\\{90, 91, 92, 93, 94, 95, 96, 97, 98, 99\\\}\\\}"
+    gdb_test -nonl "output large_2d_array" \
+	"\\\{\\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9\\\},\
+	     \\\{10, 11, 12, 13, 14, 15, 16, 17, 18, 19\\\},\
+	     \\\{20, 21, 22, 23, 24, 25, 26, 27, 28, 29\\\},\
+	     \\\{30, 31, 32, 33, 34, 35, 36, 37, 38, 39\\\},\
+	     \\\{40, 41, 42, 43, 44, 45, 46, 47, 48, 49\\\},\
+	     \\\{50, 51, 52, 53, 54, 55, 56, 57, 58, 59\\\},\
+	     \\\{60, 61, 62, 63, 64, 65, 66, 67, 68, 69\\\},\
+	     \\\{70, 71, 72, 73, 74, 75, 76, 77, 78, 79\\\},\
+	     \\\{80, 81, 82, 83, 84, 85, 86, 87, 88, 89\\\},\
+	     \\\{90, 91, 92, 93, 94, 95, 96, 97, 98, 99\\\}\\\}"
+}
+
+# Set the max-value-size so we can only print 51 elements.
+set elements 51
+set int_size [get_valueof "/d" "sizeof(large_1d_array\[0\])" "*unknown*"]
+gdb_test_no_output "set max-value-size [expr $int_size * $elements]"
+
+with_test_prefix "with reduced max-value size" {
+    gdb_test "print large_1d_array" \
+	"\r\nvalue requires $decimal bytes, which is more than max-value-size"
+    gdb_test "output large_1d_array" \
+	"\r\nvalue requires $decimal bytes, which is more than max-value-size"
+    gdb_test "print large_2d_array" \
+	"\r\nvalue requires $decimal bytes, which is more than max-value-size"
+    gdb_test "output large_2d_array" \
+	"\r\nvalue requires $decimal bytes, which is more than max-value-size"
+}
+
+gdb_test_no_output "set print elements 3"
+
+with_test_prefix "with reduced print elements" {
+    gdb_test "print large_1d_array" \
+	" = \\\{0, 1, 2\\.\\.\\.\\\}"
+    gdb_test -nonl "output large_1d_array" \
+	"\\\{0, 1, 2\\.\\.\\.\\\}"
+
+    gdb_test "print \$" \
+	" = \\\{0, 1, 2\\.\\.\\.\\\}" \
+	"print large_1d_array from history"
+    gdb_test -nonl "output \$\$" \
+	"\\\{0, 1, 2\\.\\.\\.\\\}" \
+	"output large_1d_array from history"
+
+    gdb_test "print large_2d_array" \
+	" = \\\{\\\{0, 1, 2\\.\\.\\.\\\}, \\\{10, 11, 12\\.\\.\\.\\\},\
+	    \\\{20, 21, 22\\.\\.\\.\\\}\\.\\.\\.\\\}"
+    gdb_test -nonl "output large_2d_array" \
+	"\\\{\\\{0, 1, 2\\.\\.\\.\\\}, \\\{10, 11, 12\\.\\.\\.\\\},\
+	 \\\{20, 21, 22\\.\\.\\.\\\}\\.\\.\\.\\\}"
+
+    gdb_test "print \$" \
+	" = \\\{\\\{0, 1, 2\\.\\.\\.\\\}, \\\{10, 11, 12\\.\\.\\.\\\},\
+	    \\\{20, 21, 22\\.\\.\\.\\\}\\.\\.\\.\\\}" \
+	"print large_2d_array from history"
+    gdb_test -nonl "output \$\$" \
+	"\\\{\\\{0, 1, 2\\.\\.\\.\\\}, \\\{10, 11, 12\\.\\.\\.\\\},\
+	 \\\{20, 21, 22\\.\\.\\.\\\}\\.\\.\\.\\\}" \
+	"output large_2d_array from history"
+}
+
+gdb_test_no_output "set print elements $elements"
+
+with_test_prefix "with print elements matching max-value size" {
+    gdb_test "print \$\$2" \
+	" = \\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,\
+		12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,\
+		24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,\
+		36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,\
+		48, 49, 50\\.\\.\\.\\\}" \
+	"print large_1d_array from history"
+    gdb_test -nonl "output \$\$3" \
+	"\\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,\
+	     12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,\
+	     24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,\
+	     36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,\
+	     48, 49, 50\\.\\.\\.\\\}" \
+	"output large_1d_array from history"
+
+    gdb_test "print \$\$2" \
+	" = \\\{\\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9\\\},\
+		\\\{10, 11, 12, 13, 14, 15, 16, 17, 18, 19\\\},\
+		\\\{20, 21, 22, 23, 24, 25, 26, 27, 28, 29\\\},\
+		\\\{30, 31, 32, 33, 34, 35, 36, 37, 38, 39\\\},\
+		\\\{40, 41, 42, 43, 44, 45, 46, 47, 48, 49\\\},\
+		\\\{50(?:, <unavailable>)\{9\}\\\}(?:,\
+		\\\{<unavailable>(?:, <unavailable>)\{9\}\\\})\{4\}\\\}" \
+	"print large_2d_array from history"
+    gdb_test -nonl "output \$\$3" \
+	"\\\{\\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9\\\},\
+	     \\\{10, 11, 12, 13, 14, 15, 16, 17, 18, 19\\\},\
+	     \\\{20, 21, 22, 23, 24, 25, 26, 27, 28, 29\\\},\
+	     \\\{30, 31, 32, 33, 34, 35, 36, 37, 38, 39\\\},\
+	     \\\{40, 41, 42, 43, 44, 45, 46, 47, 48, 49\\\},\
+	     \\\{50(?:, <unavailable>)\{9\}\\\}(?:,\
+	     \\\{<unavailable>(?:, <unavailable>)\{9\}\\\})\{4\}\\\}" \
+	"output large_2d_array from history"
+}
+
+gdb_test_no_output "set max-value-size unlimited"
+gdb_test_no_output "set print elements unlimited"
+gdb_test_no_output "set print repeats 3"
+
+with_test_prefix "with unlimited print elements" {
+    gdb_test "print \$\$" \
+	" = \\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,\
+		12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,\
+		24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,\
+		36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,\
+		48, 49, 50, <unavailable> <repeats 49 times>\\\}" \
+	"print large_1d_array from history"
+    gdb_test -nonl "output \$\$2" \
+	"\\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,\
+	     12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,\
+	     24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,\
+	     36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,\
+	     48, 49, 50, <unavailable> <repeats 49 times>\\\}" \
+	"output large_1d_array from history"
+
+    gdb_test "print \$\$" \
+	" = \\\{\\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9\\\},\
+		\\\{10, 11, 12, 13, 14, 15, 16, 17, 18, 19\\\},\
+		\\\{20, 21, 22, 23, 24, 25, 26, 27, 28, 29\\\},\
+		\\\{30, 31, 32, 33, 34, 35, 36, 37, 38, 39\\\},\
+		\\\{40, 41, 42, 43, 44, 45, 46, 47, 48, 49\\\},\
+		\\\{50, <unavailable> <repeats 9 times>\\\},\
+		\\\{<unavailable> <repeats 10 times>\\\}\
+		<repeats 4 times>\\\}" \
+	"print large_2d_array from history"
+    gdb_test -nonl "output \$\$2" \
+	"\\\{\\\{0, 1, 2, 3, 4, 5, 6, 7, 8, 9\\\},\
+	     \\\{10, 11, 12, 13, 14, 15, 16, 17, 18, 19\\\},\
+	     \\\{20, 21, 22, 23, 24, 25, 26, 27, 28, 29\\\},\
+	     \\\{30, 31, 32, 33, 34, 35, 36, 37, 38, 39\\\},\
+	     \\\{40, 41, 42, 43, 44, 45, 46, 47, 48, 49\\\},\
+	     \\\{50, <unavailable> <repeats 9 times>\\\},\
+	     \\\{<unavailable> <repeats 10 times>\\\}\
+	     <repeats 4 times>\\\}" \
+	"output large_2d_array from history"
+
+    gdb_test "print \$\[4\]" \
+	" = \\\{40, 41, 42, 43, 44, 45, 46, 47, 48, 49\\\}" \
+	"print available large_2d_array row from history"
+    gdb_test -nonl "output \$\$\[4\]" \
+	"\\\{40, 41, 42, 43, 44, 45, 46, 47, 48, 49\\\}" \
+	"output available large_2d_array row from history"
+
+    gdb_test "print \$\$\[5\]" \
+	" = \\\{50, <unavailable> <repeats 9 times>\\\}" \
+	"print partially available large_2d_array row from history"
+    gdb_test -nonl "output \$\$2\[5\]" \
+	"\\\{50, <unavailable> <repeats 9 times>\\\}" \
+	"output partially available large_2d_array row from history"
+
+    gdb_test "print \$\$2\[6\]" \
+	" = <unavailable>" \
+	"print unavailable large_2d_array row from history"
+    gdb_test -nonl "output \$\$3\[6\]" \
+	"<unavailable>" \
+	"output unavailable large_2d_array row from history"
+
+    gdb_test "print \$\$3\[5\]\[0\]" \
+	" = 50" \
+	"print available large_2d_array element from history"
+    gdb_test -nonl "output \$\$4\[5\]\[0\]" \
+	"50" \
+	"output available large_2d_array element from history"
+
+    gdb_test "print \$\$4\[5\]\[1\]" \
+	" = <unavailable>" \
+	"print unavailable large_2d_array element from history"
+    gdb_test -nonl "output \$\$5\[5\]\[1\]" \
+	"<unavailable>" \
+	"output unavailable large_2d_array element from history"
+
+    gdb_test "print \$\$5\[5\]\[0\] + \$\$5\[5\]\[1\]" \
+	"value is not available" \
+	"print expression referring unavailable element from history"
+    gdb_test "output \$\$5\[5\]\[0\] + \$\$5\[5\]\[1\]" \
+	"value is not available" \
+	"output expression referring unavailable element from history"
+}
Index: src/gdb/testsuite/gdb.fortran/limited-length.exp
===================================================================
--- /dev/null
+++ src/gdb/testsuite/gdb.fortran/limited-length.exp
@@ -0,0 +1,222 @@
+# Copyright 2023 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# This file tests GDB's limited length array printing.
+
+load_lib "fortran.exp"
+
+if {[skip_fortran_tests]} {
+    continue
+}
+
+standard_testfile .f90
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug f90}]} {
+    return -1
+}
+
+if {![fortran_runto_main]} {
+    perror "Could not run to main."
+    continue
+}
+
+gdb_breakpoint [gdb_get_line_number "Break Here"]
+gdb_continue_to_breakpoint "stop-here" ".*Break Here.*"
+
+with_test_prefix "with standard max-value size" {
+    gdb_test "print large_4d_array" \
+	" = \\(\\(\\(\\(1, 2, 3\\) \\(4, 5, 6\\) \\(7, 8, 9\\)\\)\
+		  \\(\\(10, 11, 12\\) \\(13, 14, 15\\) \\(16, 17, 18\\)\\)\
+		  \\(\\(19, 20, 21\\) \\(22, 23, 24\\) \\(25, 26, 27\\)\\)\\)\
+	       \\(\\(\\(28, 29, 30\\) \\(31, 32, 33\\) \\(34, 35, 36\\)\\)\
+		  \\(\\(37, 38, 39\\) \\(40, 41, 42\\) \\(43, 44, 45\\)\\)\
+		  \\(\\(46, 47, 48\\) \\(49, 50, 51\\) \\(52, 53, 54\\)\\)\\)\
+	       \\(\\(\\(55, 56, 57\\) \\(58, 59, 60\\) \\(61, 62, 63\\)\\)\
+		  \\(\\(64, 65, 66\\) \\(67, 68, 69\\) \\(70, 71, 72\\)\\)\
+		  \\(\\(73, 74, 75\\) \\(76, 77, 78\\)\
+		     \\(79, 80, 81\\)\\)\\)\\)"
+    gdb_test -nonl "output large_4d_array" \
+	"\\(\\(\\(\\(1, 2, 3\\) \\(4, 5, 6\\) \\(7, 8, 9\\)\\)\
+	       \\(\\(10, 11, 12\\) \\(13, 14, 15\\) \\(16, 17, 18\\)\\)\
+	       \\(\\(19, 20, 21\\) \\(22, 23, 24\\) \\(25, 26, 27\\)\\)\\)\
+	    \\(\\(\\(28, 29, 30\\) \\(31, 32, 33\\) \\(34, 35, 36\\)\\)\
+	       \\(\\(37, 38, 39\\) \\(40, 41, 42\\) \\(43, 44, 45\\)\\)\
+	       \\(\\(46, 47, 48\\) \\(49, 50, 51\\) \\(52, 53, 54\\)\\)\\)\
+	    \\(\\(\\(55, 56, 57\\) \\(58, 59, 60\\) \\(61, 62, 63\\)\\)\
+	       \\(\\(64, 65, 66\\) \\(67, 68, 69\\) \\(70, 71, 72\\)\\)\
+	       \\(\\(73, 74, 75\\) \\(76, 77, 78\\) \\(79, 80, 81\\)\\)\\)\\)"
+    gdb_test "print large_1d_array" \
+	" = \\(1, 2, 3, 4, 5, 6, 7, 8, 9,\
+	       10, 11, 12, 13, 14, 15, 16, 17, 18,\
+	       19, 20, 21, 22, 23, 24, 25, 26, 27,\
+	       28, 29, 30, 31, 32, 33, 34, 35, 36,\
+	       37, 38, 39, 40, 41, 42, 43, 44, 45,\
+	       46, 47, 48, 49, 50, 51, 52, 53, 54,\
+	       55, 56, 57, 58, 59, 60, 61, 62, 63,\
+	       64, 65, 66, 67, 68, 69, 70, 71, 72,\
+	       73, 74, 75, 76, 77, 78, 79, 80, 81\\)"
+    gdb_test -nonl "output large_1d_array" \
+	"\\(1, 2, 3, 4, 5, 6, 7, 8, 9,\
+	    10, 11, 12, 13, 14, 15, 16, 17, 18,\
+	    19, 20, 21, 22, 23, 24, 25, 26, 27,\
+	    28, 29, 30, 31, 32, 33, 34, 35, 36,\
+	    37, 38, 39, 40, 41, 42, 43, 44, 45,\
+	    46, 47, 48, 49, 50, 51, 52, 53, 54,\
+	    55, 56, 57, 58, 59, 60, 61, 62, 63,\
+	    64, 65, 66, 67, 68, 69, 70, 71, 72,\
+	    73, 74, 75, 76, 77, 78, 79, 80, 81\\)"
+}
+
+# Set the max-value-size so we can only print 50 elements.
+set elements 50
+set elem_size [get_valueof "/d" "sizeof(large_1d_array(1))" "*unknown*"]
+gdb_test_no_output "set max-value-size [expr $elem_size * $elements]"
+
+with_test_prefix "with reduced max-value size" {
+    gdb_test "print large_4d_array" \
+	"value requires $decimal bytes, which is more than max-value-size"
+    gdb_test "output large_4d_array" \
+	"value requires $decimal bytes, which is more than max-value-size"
+    gdb_test "print large_1d_array" \
+	"value requires $decimal bytes, which is more than max-value-size"
+    gdb_test "output large_1d_array" \
+	"value requires $decimal bytes, which is more than max-value-size"
+}
+
+with_test_prefix "with reduced print -elements flag" {
+    gdb_test "print -elements 5 -- large_4d_array" \
+	" = \\(\\(\\(\\(1, 2, 3\\) \\(4, 5, \\.\\.\\.\\)\
+		     \\.\\.\\.\\) \\.\\.\\.\\) \\.\\.\\.\\)"
+    gdb_test "print -elements 5 -- large_1d_array" \
+	" = \\(1, 2, 3, 4, 5, \\.\\.\\.\\)"
+}
+
+gdb_test_no_output "set print elements 5"
+
+with_test_prefix "with reduced print elements" {
+    gdb_test "print large_4d_array" \
+	" = \\(\\(\\(\\(1, 2, 3\\) \\(4, 5, \\.\\.\\.\\)\
+		     \\.\\.\\.\\) \\.\\.\\.\\) \\.\\.\\.\\)"
+    gdb_test -nonl "output large_4d_array" \
+	"\\(\\(\\(\\(1, 2, 3\\) \\(4, 5, \\.\\.\\.\\)\
+		  \\.\\.\\.\\) \\.\\.\\.\\) \\.\\.\\.\\)"
+
+    gdb_test "print \$" \
+	" = \\(\\(\\(\\(1, 2, 3\\) \\(4, 5, \\.\\.\\.\\)\
+		     \\.\\.\\.\\) \\.\\.\\.\\) \\.\\.\\.\\)" \
+	"print large_4d_array from history"
+    gdb_test -nonl "output \$\$" \
+	"\\(\\(\\(\\(1, 2, 3\\) \\(4, 5, \\.\\.\\.\\)\
+		  \\.\\.\\.\\) \\.\\.\\.\\) \\.\\.\\.\\)" \
+	"output large_4d_array from history"
+
+    gdb_test "print large_1d_array" \
+	" = \\(1, 2, 3, 4, 5, \\.\\.\\.\\)"
+    gdb_test -nonl "output large_1d_array" \
+	"\\(1, 2, 3, 4, 5, \\.\\.\\.\\)"
+
+    gdb_test "print \$" \
+	" = \\(1, 2, 3, 4, 5, \\.\\.\\.\\)" \
+	"print large_1d_array from history"
+    gdb_test -nonl "output \$\$" \
+	"\\(1, 2, 3, 4, 5, \\.\\.\\.\\)" \
+	"output large_1d_array from history"
+}
+
+gdb_test_no_output "set print elements $elements"
+
+with_test_prefix "with print elements matching max-value size" {
+    gdb_test "print \$\$2" \
+	" = \\(\\(\\(\\(1, 2, 3\\) \\(4, 5, 6\\) \\(7, 8, 9\\)\\)\
+		  \\(\\(10, 11, 12\\) \\(13, 14, 15\\) \\(16, 17, 18\\)\\)\
+		  \\(\\(19, 20, 21\\) \\(22, 23, 24\\) \\(25, 26, 27\\)\\)\\)\
+	       \\(\\(\\(28, 29, 30\\) \\(31, 32, 33\\) \\(34, 35, 36\\)\\)\
+		  \\(\\(37, 38, 39\\) \\(40, 41, 42\\) \\(43, 44, 45\\)\\)\
+		  \\(\\(46, 47, 48\\) \\(49, 50, \\.\\.\\.\\) \\.\\.\\.\\)\\)\
+	       \\.\\.\\.\\)" \
+	"print large_4d_array from history"
+    gdb_test -nonl "output \$\$3" \
+	"\\(\\(\\(\\(1, 2, 3\\) \\(4, 5, 6\\) \\(7, 8, 9\\)\\)\
+	       \\(\\(10, 11, 12\\) \\(13, 14, 15\\) \\(16, 17, 18\\)\\)\
+	       \\(\\(19, 20, 21\\) \\(22, 23, 24\\) \\(25, 26, 27\\)\\)\\)\
+	    \\(\\(\\(28, 29, 30\\) \\(31, 32, 33\\) \\(34, 35, 36\\)\\)\
+	       \\(\\(37, 38, 39\\) \\(40, 41, 42\\) \\(43, 44, 45\\)\\)\
+	       \\(\\(46, 47, 48\\) \\(49, 50, \\.\\.\\.\\) \\.\\.\\.\\)\\)\
+	    \\.\\.\\.\\)" \
+	"output large_4d_array from history"
+
+    gdb_test "print \$\$2" \
+	" = \\(1, 2, 3, 4, 5, 6, 7, 8, 9,\
+	       10, 11, 12, 13, 14, 15, 16, 17, 18,\
+	       19, 20, 21, 22, 23, 24, 25, 26, 27,\
+	       28, 29, 30, 31, 32, 33, 34, 35, 36,\
+	       37, 38, 39, 40, 41, 42, 43, 44, 45,\
+	       46, 47, 48, 49, 50, \\.\\.\\.\\)" \
+	"print large_1d_array from history"
+    gdb_test -nonl "output \$\$2" \
+	"\\(1, 2, 3, 4, 5, 6, 7, 8, 9,\
+	    10, 11, 12, 13, 14, 15, 16, 17, 18,\
+	    19, 20, 21, 22, 23, 24, 25, 26, 27,\
+	    28, 29, 30, 31, 32, 33, 34, 35, 36,\
+	    37, 38, 39, 40, 41, 42, 43, 44, 45,\
+	    46, 47, 48, 49, 50, \\.\\.\\.\\)" \
+	"output large_1d_array from history"
+}
+
+gdb_test_no_output "set max-value-size unlimited"
+gdb_test_no_output "set print elements unlimited"
+gdb_test_no_output "set print repeats 2"
+
+with_test_prefix "with unlimited print elements" {
+    gdb_test "print \$\$" \
+	" = \\(\\(\\(\\(1, 2, 3\\) \\(4, 5, 6\\) \\(7, 8, 9\\)\\)\
+		  \\(\\(10, 11, 12\\) \\(13, 14, 15\\) \\(16, 17, 18\\)\\)\
+		  \\(\\(19, 20, 21\\) \\(22, 23, 24\\) \\(25, 26, 27\\)\\)\\)\
+	       \\(\\(\\(28, 29, 30\\) \\(31, 32, 33\\) \\(34, 35, 36\\)\\)\
+		  \\(\\(37, 38, 39\\) \\(40, 41, 42\\) \\(43, 44, 45\\)\\)\
+		  \\(\\(46, 47, 48\\) \\(49, 50, <unavailable>\\)\
+		     \\(<unavailable>, <repeats 3 times>\\)\\)\\)\
+	       \\(\\(\\(<unavailable>, <repeats 3 times>\\)\
+		     <repeats 3 times>\\) <repeats 3 times>\\)\\)" \
+	"print large_4d_array from history"
+    gdb_test -nonl "output \$\$2" \
+	"\\(\\(\\(\\(1, 2, 3\\) \\(4, 5, 6\\) \\(7, 8, 9\\)\\)\
+	       \\(\\(10, 11, 12\\) \\(13, 14, 15\\) \\(16, 17, 18\\)\\)\
+	       \\(\\(19, 20, 21\\) \\(22, 23, 24\\) \\(25, 26, 27\\)\\)\\)\
+	    \\(\\(\\(28, 29, 30\\) \\(31, 32, 33\\) \\(34, 35, 36\\)\\)\
+	       \\(\\(37, 38, 39\\) \\(40, 41, 42\\) \\(43, 44, 45\\)\\)\
+	       \\(\\(46, 47, 48\\) \\(49, 50, <unavailable>\\)\
+		  \\(<unavailable>, <repeats 3 times>\\)\\)\\)\
+	    \\(\\(\\(<unavailable>, <repeats 3 times>\\)\
+		  <repeats 3 times>\\) <repeats 3 times>\\)\\)" \
+	"output large_4d_array from history"
+
+    gdb_test "print \$\$" \
+	" = \\(1, 2, 3, 4, 5, 6, 7, 8, 9,\
+	       10, 11, 12, 13, 14, 15, 16, 17, 18,\
+	       19, 20, 21, 22, 23, 24, 25, 26, 27,\
+	       28, 29, 30, 31, 32, 33, 34, 35, 36,\
+	       37, 38, 39, 40, 41, 42, 43, 44, 45,\
+	       46, 47, 48, 49, 50, <unavailable>, <repeats 31 times>\\)" \
+	"print large_1d_array from history"
+    gdb_test -nonl "output \$\$2" \
+	"\\(1, 2, 3, 4, 5, 6, 7, 8, 9,\
+	    10, 11, 12, 13, 14, 15, 16, 17, 18,\
+	    19, 20, 21, 22, 23, 24, 25, 26, 27,\
+	    28, 29, 30, 31, 32, 33, 34, 35, 36,\
+	    37, 38, 39, 40, 41, 42, 43, 44, 45,\
+	    46, 47, 48, 49, 50, <unavailable>, <repeats 31 times>\\)" \
+	"output large_1d_array from history"
+}
Index: src/gdb/testsuite/gdb.fortran/limited-length.f90
===================================================================
--- /dev/null
+++ src/gdb/testsuite/gdb.fortran/limited-length.f90
@@ -0,0 +1,39 @@
+! This testcase is part of GDB, the GNU debugger.
+!
+! Copyright 2023 Free Software Foundation, Inc.
+!
+! This program is free software; you can redistribute it and/or modify
+! it under the terms of the GNU General Public License as published by
+! the Free Software Foundation; either version 2 of the License, or
+! (at your option) any later version.
+!
+! This program is distributed in the hope that it will be useful,
+! but WITHOUT ANY WARRANTY; without even the implied warranty of
+! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+! GNU General Public License for more details.
+!
+! You should have received a copy of the GNU General Public License
+! along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+program main
+  integer(kind=8), dimension (3, 3, 3, 3) :: large_4d_array = reshape ((/ &
+       1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, &
+       18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, &
+       33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, &
+       48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, &
+       63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, &
+       78, 79, 80, 81/), (/3, 3, 3, 3/))
+
+  integer(kind=8), dimension (81) :: large_1d_array = reshape ((/ &
+       1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, &
+       18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, &
+       33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, &
+       48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, &
+       63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, &
+       78, 79, 80, 81/), (/81/))
+
+  print *, ""
+  print *, ""	! Break Here
+  print *, large_4d_array
+  print *, large_1d_array
+end program main
Index: src/gdb/valprint.c
===================================================================
--- src.orig/gdb/valprint.c
+++ src/gdb/valprint.c
@@ -2018,13 +2018,21 @@ value_print_array_elements (struct value
 	 UINT_MAX (unlimited).  */
       if (options->repeat_count_threshold < UINT_MAX)
 	{
+	  bool unavailable = value_entirely_unavailable (element);
+	  bool available = value_entirely_available (element);
+
 	  while (rep1 < len)
 	    {
 	      struct value *rep_elt
 		= value_from_component_bitsize (val, elttype,
 						rep1 * bit_stride,
 						bit_stride);
-	      if (!value_contents_eq (element, rep_elt))
+	      bool repeated = ((available
+				&& value_entirely_available (rep_elt)
+				&& value_contents_eq (element, rep_elt))
+			       || (unavailable
+				   && value_entirely_unavailable (rep_elt)));
+	      if (!repeated)
 		break;
 	      ++reps;
 	      ++rep1;
Index: src/gdb/value.c
===================================================================
--- src.orig/gdb/value.c
+++ src/gdb/value.c
@@ -369,6 +369,14 @@ struct value
      treated pretty much the same, except not-saved registers have a
      different string representation and related error strings.  */
   std::vector<range> optimized_out;
+
+  /* This is only non-zero for values of TYPE_CODE_ARRAY and if the size of
+     the array in inferior memory is greater than max_value_size.  If these
+     conditions are met then, when the value is loaded from the inferior
+     GDB will only load a portion of the array into memory, and
+     limited_length will be set to indicate the length in octets that were
+     loaded from the inferior.  */
+  ULONGEST limited_length = 0;
 };
 
 /* See value.h.  */
@@ -1046,6 +1054,93 @@ check_type_length_before_alloc (const st
     }
 }
 
+/* When this has a value, it is used to limit the number of array elements
+   of an array that are loaded into memory when an array value is made
+   non-lazy.  */
+static gdb::optional<int> array_length_limiting_element_count;
+
+/* See value.h.  */
+scoped_array_length_limiting::scoped_array_length_limiting (int elements)
+{
+  m_old_value = array_length_limiting_element_count;
+  array_length_limiting_element_count.emplace (elements);
+}
+
+/* See value.h.  */
+scoped_array_length_limiting::~scoped_array_length_limiting ()
+{
+  array_length_limiting_element_count = m_old_value;
+}
+
+/* Find the inner element type for ARRAY_TYPE.  */
+
+static struct type *
+find_array_element_type (struct type *array_type)
+{
+  array_type = check_typedef (array_type);
+  gdb_assert (array_type->code () == TYPE_CODE_ARRAY);
+
+  if (current_language->la_language == language_fortran)
+    while (array_type->code () == TYPE_CODE_ARRAY)
+      {
+	array_type = array_type->target_type ();
+	array_type = check_typedef (array_type);
+      }
+  else
+    {
+      array_type = array_type->target_type ();
+      array_type = check_typedef (array_type);
+    }
+
+  return array_type;
+}
+
+/* Return the limited length of ARRAY_TYPE, which must be of
+   TYPE_CODE_ARRAY.  This function can only be called when the global
+   ARRAY_LENGTH_LIMITING_ELEMENT_COUNT has a value.
+
+   The limited length of an array is the smallest of either (1) the total
+   size of the array type, or (2) the array target type multiplies by the
+   array_length_limiting_element_count.  */
+
+static ULONGEST
+calculate_limited_array_length (struct type *array_type)
+{
+  gdb_assert (array_length_limiting_element_count.has_value ());
+
+  array_type = check_typedef (array_type);
+  gdb_assert (array_type->code () == TYPE_CODE_ARRAY);
+
+  struct type *elm_type = find_array_element_type (array_type);
+  ULONGEST len = (elm_type->length ()
+		  * (*array_length_limiting_element_count));
+  len = std::min (len, array_type->length ());
+
+  return len;
+}
+
+/* Try to limit ourselves to only fetching the limited number of
+   elements.  However, if this limited number of elements still
+   puts us over max_value_size, then we still throw an error.  */
+
+static bool
+set_limited_array_length (struct value *val)
+{
+  ULONGEST limit = val->limited_length;
+  ULONGEST len = value_type (val)->length ();
+
+  if (array_length_limiting_element_count.has_value ())
+    len = calculate_limited_array_length (value_type (val));
+
+  if (limit != 0 && len > limit)
+    len = limit;
+  if (len > max_value_size)
+    return false;
+
+  val->limited_length = max_value_size;
+  return true;
+}
+
 /* Allocate the contents of VAL if it has not been allocated yet.
    If CHECK_SIZE is true, then apply the usual max-value-size checks.  */
 
@@ -1054,10 +1149,26 @@ allocate_value_contents (struct value *v
 {
   if (!val->contents)
     {
+      struct type *enclosing_type = value_enclosing_type (val);
+      ULONGEST len = enclosing_type->length ();
+
       if (check_size)
-	check_type_length_before_alloc (val->enclosing_type);
-      val->contents.reset
-	((gdb_byte *) xzalloc (val->enclosing_type->length ()));
+	{
+	  /* If we are allocating the contents of an array, which
+	     is greater in size than max_value_size, and there is
+	     an element limit in effect, then we can possibly try
+	     to load only a sub-set of the array contents into
+	     GDB's memory.  */
+	  if (value_type (val) == enclosing_type
+	      && value_type (val)->code () == TYPE_CODE_ARRAY
+	      && len > max_value_size
+	      && set_limited_array_length (val))
+	    len = val->limited_length;
+	  else
+	    check_type_length_before_alloc (enclosing_type);
+	}
+
+      val->contents.reset ((gdb_byte *) xzalloc (len));
     }
 }
 
@@ -1789,10 +1900,7 @@ value_copy (const value *arg, bool check
   struct type *encl_type = value_enclosing_type (arg);
   struct value *val;
 
-  if (value_lazy (arg))
-    val = allocate_value_lazy (encl_type);
-  else
-    val = allocate_value (encl_type, check_size);
+  val = allocate_value_lazy (encl_type);
   val->type = arg->type;
   VALUE_LVAL (val) = arg->lval;
   val->location = arg->location;
@@ -1808,17 +1916,41 @@ value_copy (const value *arg, bool check
   val->initialized = arg->initialized;
   val->unavailable = arg->unavailable;
   val->optimized_out = arg->optimized_out;
+  val->parent = arg->parent;
+  val->limited_length = arg->limited_length;
 
-  if (!value_lazy (val) && !value_entirely_optimized_out (val))
+  if (!value_lazy (val)
+      && !(value_entirely_optimized_out (val)
+	   || value_entirely_unavailable (val)))
     {
       gdb_assert (arg->contents != nullptr);
-      ULONGEST length = value_enclosing_type (arg)->length ();
+      allocate_value_contents (val, check_size);
+
+      /* We need to handle the case where the new VAL has its content
+	 buffer limited, but to a different length, than the original
+	 ARG value.  This all gets rather messy.  */
+      ULONGEST src_len, dst_len;
+      if (val->limited_length > 0)
+	dst_len = val->limited_length;
+      else
+	dst_len = value_enclosing_type (val)->length ();
+
+      if (arg->limited_length > 0)
+	src_len = val->limited_length;
+      else
+	src_len = value_enclosing_type (arg)->length ();
+
+      ULONGEST len = std::min (src_len, dst_len);
+      gdb::array_view<gdb_byte> val_contents
+	= value_contents_all_raw (val).slice (0, len);
       const auto &arg_view
-	= gdb::make_array_view (arg->contents.get (), length);
-      copy (arg_view, value_contents_all_raw (val));
+	= gdb::make_array_view (arg->contents.get (), len);
+      copy (arg_view, val_contents);
+
+      if (dst_len < src_len)
+	mark_value_bytes_unavailable (val, dst_len, (src_len - dst_len));
     }
 
-  val->parent = arg->parent;
   if (VALUE_LVAL (val) == lval_computed)
     {
       const struct lval_funcs *funcs = val->location.computed.funcs;
@@ -1961,20 +2093,40 @@ set_value_component_location (struct val
 int
 record_latest_value (struct value *val)
 {
+  struct type *enclosing_type = value_enclosing_type (val);
+  struct type *type = value_type (val);
+
   /* We don't want this value to have anything to do with the inferior anymore.
      In particular, "set $1 = 50" should not affect the variable from which
      the value was taken, and fast watchpoints should be able to assume that
      a value on the value history never changes.  */
   if (value_lazy (val))
-    value_fetch_lazy (val);
+    {
+      /* We know that this is a _huge_ array, any attempt to fetch this
+         is going to cause GDB to throw an error.  However, to allow
+         the array to still be displayed we fetch its contents up to
+         `max_value_size' and mark anything beyond "unavailable" in
+         the history.  */
+      if (type->code () == TYPE_CODE_ARRAY
+	  && type->length () > max_value_size
+	  && array_length_limiting_element_count.has_value ()
+	  && enclosing_type == type
+	  && calculate_limited_array_length (type) <= max_value_size)
+	val->limited_length = max_value_size;
+
+      value_fetch_lazy (val);
+    }
 
   /* Don't pretend we have anything available there in the history beyond
      the boundaries of the value recorded.  It's not like inferior memory
      where there is actual stuff underneath.  */
-  ULONGEST length = value_enclosing_type (val)->length ();
+  ULONGEST length = enclosing_type->length ();
   mark_value_bits_unavailable (val, LONGEST_MIN, 0 ^ LONGEST_MIN);
   mark_value_bits_unavailable (val, length * TARGET_CHAR_BIT,
 			       LONGEST_MAX - length * TARGET_CHAR_BIT);
+  if (val->limited_length != 0)
+    mark_value_bytes_unavailable (val, val->limited_length,
+				  length - val->limited_length);
 
   /* We preserve VALUE_LVAL so that the user can find out where it was fetched
      from.  This is a bit dubious, because then *&$1 does not just return $1
@@ -4071,10 +4223,23 @@ value_fetch_lazy_memory (struct value *v
   CORE_ADDR addr = value_address (val);
   struct type *type = check_typedef (value_enclosing_type (val));
 
-  if (type->length ())
-      read_value_memory (val, 0, value_stack (val),
-			 addr, value_contents_all_raw (val).data (),
-			 type_length_units (type));
+  /* Figure out how much we should copy from memory.  Usually, this is just
+     the size of the type, but, for arrays, we might only be loading a
+     small part of the array (this is only done for very large arrays).  */
+  int len = 0;
+  if (val->limited_length > 0)
+    {
+      gdb_assert (value_type (val)->code () == TYPE_CODE_ARRAY);
+      len = val->limited_length;
+    }
+  else if (type->length () > 0)
+    len = type_length_units (type);
+
+  gdb_assert (len >= 0);
+
+  if (len > 0)
+    read_value_memory (val, 0, value_stack (val), addr,
+		       value_contents_all_raw (val).data (), len);
 }
 
 /* Helper for value_fetch_lazy when the value is in a register.  */
Index: src/gdb/value.h
===================================================================
--- src.orig/gdb/value.h
+++ src/gdb/value.h
@@ -1235,4 +1235,21 @@ extern void finalize_values ();
    of floating-point, fixed-point, or integer type.  */
 extern gdb_mpq value_to_gdb_mpq (struct value *value);
 
+/* While an instance of this class is live, and array values that are
+   created, that are larger than max_value_size, will be restricted in size
+   to a particular number of elements.  */
+
+struct scoped_array_length_limiting
+{
+  /* Limit any large array values to only contain ELEMENTS elements.  */
+  scoped_array_length_limiting (int elements);
+
+  /* Restore the previous array value limit.  */
+  ~scoped_array_length_limiting ();
+
+private:
+  /* Used to hold the previous array value element limit.  */
+  gdb::optional<int> m_old_value;
+};
+
 #endif /* !defined (VALUE_H) */

Re: [PATCH v2 5/5] GDB: Introduce limited array lengths while printing values

[Eli Zaretskii]

> Date: Thu, 12 Jan 2023 09:02:23 +0000 (GMT)
> From: "Maciej W. Rozycki" <macro@embecosm.com>
> cc: Andrew Burgess <aburgess@redhat.com>, Tom Tromey <tom@tromey.com>, 
>  Richard Bunt <Richard.Bunt@arm.com>
> 
> --- src.orig/gdb/NEWS
> +++ src/gdb/NEWS
> @@ -354,6 +354,12 @@ GDB now supports floating-point on Loong
>    Disabling this can cause a performance penalty when there are a lot of
>    symbols to load, but is useful for debugging purposes.
>  
> +* The 'set print elements' setting now helps when printing large arrays.
> +  If an array would otherwise exceed max-value-size, but 'print elements'
> +  is set such that the number of elements to print is less than or equal
> +  to 'max-value-size', GDB will now still print the array, however only
> +  'max-value-size' worth of data will be added into the value history.

The wording here needs to be changed, because max-value-size is not
about the number of elements, it's about the amount of memory needed
for those elements.  So this part:

                                                       but 'print elements'
     is set such that the number of elements to print is less than or equal
     to 'max-value-size'

should be reworded.

> --- src.orig/gdb/doc/gdb.texinfo
> +++ src/gdb/doc/gdb.texinfo
> @@ -11756,6 +11756,14 @@ When @value{GDBN} starts, this limit is
>  Setting @var{number-of-elements} to @code{unlimited} or zero means
>  that the number of elements to print is unlimited.
>  
> +When printing very large arrays, whose size is greater than
> +@code{max-value-size} (@pxref{set max-value-size,,max-value-size}),
> +if the @code{print elements} is set such that the size of the elements
> +being printed is less than or equal to @code{max-value-size}, then
> +@value{GDBN} will print the array (up to the @code{print elements} limit),
> +and only @code{max-value-size} worth of data will be added into the value
> +history (@pxref{Value History, ,Value History}).
> +
>  @item show print elements
>  Display the number of elements of a large array that @value{GDBN} will print.
>  
> @@ -14171,6 +14179,7 @@ may indicate a value that is incorrectly
>  @value{GDBN} to try and allocate an overly large amount of memory.
>  
>  @table @code
> +@anchor{set max-value-size}
>  @kindex set max-value-size
>  @item set max-value-size @var{bytes}
>  @itemx set max-value-size unlimited

This part is OK.

Thanks.

Re: [PATCH v2 5/5] GDB: Introduce limited array lengths while printing values

[Maciej W. Rozycki]

On Thu, 12 Jan 2023, Eli Zaretskii wrote:

> > --- src.orig/gdb/NEWS
> > +++ src/gdb/NEWS
> > @@ -354,6 +354,12 @@ GDB now supports floating-point on Loong
> >    Disabling this can cause a performance penalty when there are a lot of
> >    symbols to load, but is useful for debugging purposes.
> >  
> > +* The 'set print elements' setting now helps when printing large arrays.
> > +  If an array would otherwise exceed max-value-size, but 'print elements'
> > +  is set such that the number of elements to print is less than or equal
> > +  to 'max-value-size', GDB will now still print the array, however only
> > +  'max-value-size' worth of data will be added into the value history.
> 
> The wording here needs to be changed, because max-value-size is not
> about the number of elements, it's about the amount of memory needed
> for those elements.  So this part:
> 
>                                                        but 'print elements'
>      is set such that the number of elements to print is less than or equal
>      to 'max-value-size'
> 
> should be reworded.

 Thank you for your review, and thanks for catching this subtlety.  I'll 
replace "number" with "size" above just as in the manual, whether in the 
final version committed or in the next iteration (as appropriate).

  Maciej