[Bug gdb/26680] New: FAIL: gdb.ada/variant.exp: scenario=minimal: fetch type for python (GDB internal error)

[Bug gdb/26680] New: FAIL: gdb.ada/variant.exp: scenario=minimal: fetch type for python (GDB internal error)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26680

            Bug ID: 26680
           Summary: FAIL: gdb.ada/variant.exp: scenario=minimal: fetch
                    type for python (GDB internal error)
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

With current trunk (at commit e37c930f9e "gcc-4.4.7 warning fixes"), I see
these probably related internal errors:
...
FAIL: gdb.ada/variant.exp: scenario=minimal: fetch type for python (GDB
internal error)
FAIL: gdb.ada/variant.exp: scenario=minimal: python print(t.dynamic)
FAIL: gdb.ada/variant.exp: scenario=minimal: python print(t['onevalue'].bitpos)
FAIL: gdb.dwarf2/variant.exp: print as Simple (GDB internal error)
FAIL: gdb.dwarf2/variant.exp: print as Defaulted (GDB internal error)
FAIL: gdb.dwarf2/variant.exp: print as Univariant (GDB internal error)
FAIL: gdb.dwarf2/variant.exp: print as Negative (GDB internal error)
...

Looking at gdb.dwarf2/variant.exp:
...
(gdb) PASS: gdb.dwarf2/variant.exp: set language rust
print *($1 as *mut Simple)^M
/home/vries/gdb_versions/devel/src/gdb/dwarf2/attribute.h:90: internal-error:
ULONGEST attribute::as_unsigned() const: Assertion `form_is_unsigned ()'
failed.^M
A problem internal to GDB has been detected,^M
further debugging may prove unreliable.^M
...

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[Bug gdb/26680] FAIL: gdb.ada/variant.exp: scenario=minimal: fetch type for python (GDB internal error)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26680

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
Reproduce:
...
gdb \
  -batch \
  ./outputs/gdb.dwarf2/variant/variant \
  -ex "break func" \
  -ex run \
  -ex "print (void *) buffer" \
  -ex "set language rust" \
  -ex "print *(\$1 as *mut Simple)"
...

Backtrace:
...
(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1  0x00007ffff4b96b01 in __GI_abort () at abort.c:79
#2  0x00000000007fe516 in dump_core () at
/home/vries/gdb_versions/devel/src/gdb/utils.c:204
#3  0x0000000000803133 in internal_vproblem(internal_problem *, const char *,
int, const char *, typedef __va_list_tag __va_list_tag *) (
    problem=problem@entry=0x10846c0 <internal_error_problem>, file=<optimized
out>, line=90, 
    fmt=<optimized out>, ap=ap@entry=0x7fffffffc3b8)
    at /home/vries/gdb_versions/devel/src/gdb/utils.c:414
#4  0x00000000008032b9 in internal_verror (file=<optimized out>,
line=<optimized out>, 
    fmt=<optimized out>, ap=ap@entry=0x7fffffffc3b8)
    at /home/vries/gdb_versions/devel/src/gdb/utils.c:439
#5  0x00000000009b8412 in internal_error (
    file=file@entry=0xa4bd98
"/home/vries/gdb_versions/devel/src/gdb/dwarf2/attribute.h", 
    line=line@entry=90, fmt=<optimized out>)
    at /home/vries/gdb_versions/devel/src/gdbsupport/errors.cc:55
#6  0x000000000056e1d8 in attribute::as_unsigned (this=0x2220a88)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/attribute.h:90
#7  handle_variant (cu=0x1d6eee0, template_args=0x7fffffffc6f0,
fi=0x7fffffffc810, 
    type=0x21ba210, die=0x2220a60)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:16190
#8  handle_struct_member_die (child_die=child_die@entry=0x2220a60, 
    type=type@entry=0x21ba210, fi=fi@entry=0x7fffffffc810, 
    template_args=template_args@entry=0x7fffffffc6f0, cu=cu@entry=0x1d6eee0)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:16250
#9  0x000000000056de56 in handle_variant_part (cu=0x1d6eee0,
template_args=0x7fffffffc6f0, 
    fi=0x7fffffffc810, type=0x21ba210, die=0x1ff6ad0)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:16141
#10 handle_struct_member_die (child_die=child_die@entry=0x22209c0,
type=0x21ba210, 
    fi=fi@entry=0x7fffffffc810,
template_args=template_args@entry=0x7fffffffc6f0, 
    cu=cu@entry=0x1d6eee0) at
/home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:16248
#11 0x000000000056f0a1 in process_structure_scope (cu=0x1d6eee0, die=0x2220970)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:16277
#12 process_die (die=die@entry=0x2220970, cu=cu@entry=0x1d6eee0)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:10183
#13 0x000000000056f62f in read_file_scope (cu=0x1d6eee0, die=0x221fe00)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:11138
#14 process_die (die=0x221fe00, cu=cu@entry=0x1d6eee0)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:10155
#15 0x0000000000571aa5 in process_full_comp_unit (pretend_language=<optimized
out>, 
    cu=0x1d6eee0) at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:9925
#16 process_queue (per_objfile=0x1a786f0)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:9154
#17 dw2_do_instantiate_symtab (per_cu=<optimized out>, 
    per_objfile=per_objfile@entry=0x1a786f0,
skip_partial=skip_partial@entry=false)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:2433
#18 0x00000000005732af in dwarf2_psymtab::expand_psymtab (this=0x1d72a00,
objfile=0x1a8f9b0)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:9183
#19 0x0000000000554549 in dwarf2_psymtab::read_symtab (this=0x1d72a00,
objfile=0x1a8f9b0)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:9031
#20 0x00000000006af3e1 in psymtab_to_symtab (objfile=objfile@entry=0x1a8f9b0, 
    pst=pst@entry=0x1d72a00) at
/home/vries/gdb_versions/devel/src/gdb/psymtab.c:756
#21 0x00000000006b1dba in psym_lookup_symbol (objfile=0x1a8f9b0,
block_index=STATIC_BLOCK, 
    name=0x217a9d0 "Simple", domain=STRUCT_DOMAIN)
    at /home/vries/gdb_versions/devel/src/gdb/psymtab.c:483
#22 0x0000000000793e4c in lookup_symbol_via_quick_fns (domain=STRUCT_DOMAIN, 
    name=0x217a9d0 "Simple", block_index=STATIC_BLOCK, objfile=0x1a8f9b0)
    at /home/vries/gdb_versions/devel/src/gdb/symtab.c:2373
#23 lookup_symbol_in_objfile (objfile=0x1a8f9b0, block_index=STATIC_BLOCK, 
    name=0x217a9d0 "Simple", domain=STRUCT_DOMAIN)
    at /home/vries/gdb_versions/devel/src/gdb/symtab.c:2521
#24 0x0000000000794060 in lookup_symbol_global_or_static_iterator_cb (
    objfile=<optimized out>, cb_data=0x7fffffffd0a0)
    at /home/vries/gdb_versions/devel/src/gdb/symtab.c:2595
#25 0x000000000076006c in svr4_iterate_over_objfiles_in_search_order (
    gdbarch=<optimized out>, 
    cb=0x794040 <lookup_symbol_global_or_static_iterator_cb(objfile*, void*)>, 
    cb_data=0x7fffffffd0a0, current_objfile=0x0)
    at /home/vries/gdb_versions/devel/src/gdb/solib-svr4.c:3248
#26 0x000000000078e72e in lookup_global_or_static_symbol (
    name=name@entry=0x217a9d0 "Simple",
block_index=block_index@entry=STATIC_BLOCK, 
    objfile=objfile@entry=0x0, domain=domain@entry=STRUCT_DOMAIN)
    at /home/vries/gdb_versions/devel/src/gdb/symtab.c:2641
#27 0x0000000000793649 in lookup_static_symbol (domain=STRUCT_DOMAIN, 
    name=0x217a9d0 "Simple") at
/home/vries/gdb_versions/devel/src/gdb/symtab.c:2659
#28 lookup_symbol_aux (name=0x217a9d0 "Simple", 
    match_type=match_type@entry=symbol_name_match_type::FULL,
block=block@entry=0x1d9c1b0, 
    domain=domain@entry=STRUCT_DOMAIN, language=language@entry=language_rust, 
    is_a_field_of_this=is_a_field_of_this@entry=0x0)
    at /home/vries/gdb_versions/devel/src/gdb/symtab.c:2103
#29 0x0000000000793703 in lookup_symbol_in_language (name=<optimized out>,
block=0x1d9c1b0, 
    domain=domain@entry=STRUCT_DOMAIN, lang=language_rust, 
    is_a_field_of_this=is_a_field_of_this@entry=0x0)
    at /home/vries/gdb_versions/devel/src/gdb/symtab.c:1884
#30 0x0000000000793762 in lookup_symbol (name=<optimized out>, block=<optimized
out>, 
    domain=domain@entry=STRUCT_DOMAIN,
is_a_field_of_this=is_a_field_of_this@entry=0x0)
    at /home/vries/gdb_versions/devel/src/gdb/symtab.c:1896
#31 0x0000000000736914 in rust_parser::rust_lookup_type
(this=this@entry=0x7fffffffd470, 
    name=<optimized out>, name@entry=0x217a9d0 "Simple", block=<optimized out>)
    at /home/vries/gdb_versions/devel/src/gdb/rust-exp.y:2020
#32 0x000000000073a8e6 in rust_parser::convert_ast_to_type
(this=0x7fffffffd470, 
    operation=<optimized out>) at
/home/vries/gdb_versions/devel/src/gdb/rust-exp.y:2063
#33 0x000000000073a981 in rust_parser::convert_ast_to_type
(this=0x7fffffffd470, 
    operation=0x217aa20) at
/home/vries/gdb_versions/devel/src/gdb/rust-exp.y:2093
#34 0x000000000073b241 in rust_parser::convert_ast_to_expression
(this=0x7fffffffd470, 
    operation=0x217aa60, top=0x217aaa0, want_type=want_type@entry=false)
    at /home/vries/gdb_versions/devel/src/gdb/rust-exp.y:2313
#35 0x000000000073b29b in rust_parser::convert_ast_to_expression (
    this=this@entry=0x7fffffffd470, operation=0x217aaa0, top=0x217aaa0, 
    want_type=want_type@entry=false)
    at /home/vries/gdb_versions/devel/src/gdb/rust-exp.y:2256
#36 0x000000000073b831 in rust_parse (state=0x7fffffffd590)
    at /home/vries/gdb_versions/devel/src/gdb/rust-exp.y:2549
#37 0x0000000000681cb7 in parse_exp_in_context
(stringptr=stringptr@entry=0x7fffffffd668, 
    pc=pc@entry=0, block=block@entry=0x0, comma=comma@entry=0, 
    out_subexp=out_subexp@entry=0x0, tracker=0x7fffffffd580, cstate=0x0,
void_context_p=0, 
    this=<optimized out>) at
/home/vries/gdb_versions/devel/src/gdb/parse.c:1121
#38 0x0000000000682035 in parse_exp_1 (tracker=0x0, comma=0, block=0x0, pc=0, 
    stringptr=0x7fffffffd668) at
/home/vries/gdb_versions/devel/src/gdb/parse.c:1030
#39 parse_expression (string=<optimized out>, tracker=tracker@entry=0x0)
    at /home/vries/gdb_versions/devel/src/gdb/parse.c:1165
#40 0x00000000006a5334 in print_command_1 (args=<optimized out>, voidprint=1)
    at /home/vries/gdb_versions/devel/src/gdb/printcmd.c:1223
#41 0x00000000004d4f22 in cmd_func (cmd=<optimized out>, args=<optimized out>, 
    from_tty=<optimized out>) at
/home/vries/gdb_versions/devel/src/gdb/cli/cli-decode.c:2181
#42 0x00000000007c1970 in execute_command (p=<optimized out>, 
    p@entry=<error reading variable: value has been optimized out>, from_tty=0, 
    from_tty@entry=<error reading variable: value has been optimized out>)
    at /home/vries/gdb_versions/devel/src/gdb/top.c:664
#43 0x000000000063d07e in catch_command_errors (command=<optimized out>, 
    arg=<optimized out>, from_tty=<optimized out>)
    at /home/vries/gdb_versions/devel/src/gdb/main.c:457
#44 0x000000000063ed07 in captured_main_1
(context=context@entry=0x7fffffffda60)
    at /home/vries/gdb_versions/devel/src/gdb/main.c:1218
#45 0x000000000063f2bb in captured_main (data=data@entry=0x7fffffffda60)
    at /home/vries/gdb_versions/devel/src/gdb/main.c:1243
#46 gdb_main (args=args@entry=0x7fffffffda80)
    at /home/vries/gdb_versions/devel/src/gdb/main.c:1268
#47 0x000000000041b745 in main (argc=<optimized out>, argv=<optimized out>)
    at /home/vries/gdb_versions/devel/src/gdb/gdb.c:32
...

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[Bug gdb/26680] FAIL: gdb.ada/variant.exp: scenario=minimal: fetch type for python (GDB internal error)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26680

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
Triggered here:
...
#6  0x000000000056e1d8 in attribute::as_unsigned (this=0x225c818)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/attribute.h:90
90          gdb_assert (form_is_unsigned ());
...
because form_is_unsigned is false, given that form == DW_FORM_sdata:
...
(gdb) p *this
$5 = {name = DW_AT_discr_value, requires_reprocessing = 0, form =
DW_FORM_sdata, 
  string_is_canonical = 0, u = {
    str = 0xffffffffffffffff <error: Cannot access memory at address
0xffffffffffffffff>, 
    blk = 0xffffffffffffffff, unsnd = 18446744073709551615, snd = -1, 
    addr = 18446744073709551615, signature = 18446744073709551615}}
...

It's called from:
...
(gdb) 
#7  handle_variant (cu=0x1d6eee0, template_args=0x7fffffffc6f0,
fi=0x7fffffffc810, 
    type=0x218ab80, die=0x217bc50)
    at /home/vries/gdb_versions/devel/src/gdb/dwarf2/read.c:16190
16190       variant.discriminant_value = discr->as_unsigned ();
...
which I guess triggers on this bit from the test-case:
...
                    variant {
                        {discr_value -1 sdata}
                    } {
...

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[Bug gdb/26680] FAIL: gdb.ada/variant.exp: scenario=minimal: fetch type for python (GDB internal error)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26680

--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
Tentative patch:
...
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index bcac94ed36..ba98fe6ff6 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -16187,7 +16187,17 @@ handle_variant (struct die_info *die, struct type
*type,
        variant.discr_list_data = discr->as_block ();
     }
   else
-    variant.discriminant_value = discr->as_unsigned ();
+    if (discr->form_is_unsigned ())
+      variant.discriminant_value = discr->as_unsigned ();
+    else
+      {
+       union {
+         ULONGEST u;
+         LONGEST i;
+       } val;
+       val.i = discr->as_signed ();;
+       variant.discriminant_value = val.u;
+      }

   for (die_info *variant_child = die->child;
        variant_child != NULL;
...

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[Bug gdb/26680] FAIL: gdb.ada/variant.exp: scenario=minimal: fetch type for python (GDB internal error)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26680

--- Comment #4 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom de Vries from comment #3)
> Tentative patch:

Fixes all mentioned internal-errors.

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[Bug gdb/26680] FAIL: gdb.ada/variant.exp: scenario=minimal: fetch type for python (GDB internal error)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26680

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org

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[Bug gdb/26680] FAIL: gdb.ada/variant.exp: scenario=minimal: fetch type for python (GDB internal error)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26680

--- Comment #5 from Tom de Vries <vries at gcc dot gnu.org> ---
How about something like this:
...
diff --git a/gdb/dwarf2/attribute.h b/gdb/dwarf2/attribute.h
index aded129764..1c431f1791 100644
--- a/gdb/dwarf2/attribute.h
+++ b/gdb/dwarf2/attribute.h
@@ -92,6 +92,13 @@ struct attribute
     return u.unsnd;
   }

+  /* Return the unsigned value.  Requires that reprocessing not be needed.  */
+  ULONGEST as_unsigned_relaxed () const
+  {
+    gdb_assert (!requires_reprocessing);
+    return u.unsnd;
+  }
+
   /* Return non-zero if ATTR's value is a section offset --- classes
      lineptr, loclistptr, macptr or rangelistptr --- or zero, otherwise.
      You may use the as_unsigned method to retrieve such offsets.
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index bcac94ed36..b287441101 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -16187,7 +16187,7 @@ handle_variant (struct die_info *die, struct type
*type,
        variant.discr_list_data = discr->as_block ();
     }
   else
-    variant.discriminant_value = discr->as_unsigned ();
+    variant.discriminant_value = discr->as_unsigned_relaxed ();

   for (die_info *variant_child = die->child;
        variant_child != NULL;
...

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[Bug gdb/26680] FAIL: gdb.ada/variant.exp: scenario=minimal: fetch type for python (GDB internal error)

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26680

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
           Assignee|unassigned at sourceware dot org   |tromey at sourceware dot org
             Status|NEW                         |RESOLVED

--- Comment #6 from Tom Tromey <tromey at sourceware dot org> ---
Sorry about this.  I fixed it before I was aware of this bug:

https://sourceware.org/pipermail/gdb-patches/2020-September/172207.html

I did it using the existing constant_value method.

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[Bug gdb/26680] FAIL: gdb.ada/variant.exp: scenario=minimal: fetch type for python (GDB internal error)

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26680

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.1

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