[PATCH] DWARFv5: Handle DW_MACRO_define_strx and DW_MACRO_undef_strx macro entries.

[PATCH] DWARFv5: Handle DW_MACRO_define_strx and DW_MACRO_undef_strx macro entries.

[nitachra]

GDB is not able to print the macro values with -gdwarf-5 for clang
generated binaries. Clang is emitting DW_MACRO_define_strx and
DW_MACRO_undef_strx entries in .debug_macro section which are not
supported in GDB. This patch handles them.

DW_MACRO_define_strx and DW_MACRO_undef_strx are added in DWARFv5.
They have two operands. The first operand encodes the line number of
the #define or #undef macro directive. The second operand identifies
a string; it is represented using an unsigned LEB128 encoded value,
which is interpreted as a zero-based index into an array of offsets
in the .debug_str_offsets section. This is as per the section 6.3.2.1
of Dwarf Debugging Information Format Version 5.

Test case used:
 #define MAX_SIZE 10
int main(void)
{
   int size = 0;
   size = size + MAX_SIZE;

   printf("\n The value of size is [%d]\n",size);

   return 0;
}

clang -gdwarf-5 -fdebug-macro  macro.c -o macro.out

Before the patch:

gdb -q  macro.out -ex "start" -ex "p MAX_SIZE"
Reading symbols from macro.out...
Temporary breakpoint 1 at 0x4004df: file macro.c, line 7.
Starting program: /home/nitika/workspace/macro.out

Temporary breakpoint 1, main () at macro.c:7
7          int size = 0;
No symbol "MAX_SIZE" in current context.

After the patch:

gdb -q  macro.out -ex "start" -ex "p MAX_SIZE"
Reading symbols from macro.out...
Temporary breakpoint 1 at 0x4004df: file macro.c, line 7.
Starting program: /home/nitika/workspace/macro.out

Temporary breakpoint 1, main () at macro.c:7
7          int size = 0;
$1 = 10

Tested by running the testsuite before and after the patch with
 -gdwarf-5 and there is no increase in the number of test cases
that fails. Used clang 11.0.0.

gdb/dwarf2/ChangeLog:

*macro.c (dwarf_decode_macro_bytes): Handle DW_MACRO_define_strx
 and DW_MACRO_undef_strx.
 (dwarf_decode_macros): Likewise
*read.c (dwarf_decode_macros): Pass str_offsets_base in the parameters
 which is the value of DW_AT_str_offsets_base.
*macro.h (dwarf_decode_macros): Modify the definition to include
 str_offsets_base.

gdb/ChangeLog:

*macrotab.c (macro_lookup_inclusion): In DWARF version 5 filename
includes the full directory path.
---
 gdb/dwarf2/macro.c | 63 +++++++++++++++++++++++++++++++++++++++++++---
 gdb/dwarf2/macro.h |  1 +
 gdb/dwarf2/read.c  |  4 ++-
 gdb/macrotab.c     |  3 ++-
 4 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/gdb/dwarf2/macro.c b/gdb/dwarf2/macro.c
index d047d806f8..2f5f3aa827 100644
--- a/gdb/dwarf2/macro.c
+++ b/gdb/dwarf2/macro.c
@@ -427,6 +427,7 @@ dwarf_decode_macro_bytes (dwarf2_per_objfile *per_objfile,
 			  const struct dwarf2_section_info *section,
 			  int section_is_gnu, int section_is_dwz,
 			  unsigned int offset_size,
+			  ULONGEST str_offsets_base,
 			  htab_t include_hash)
 {
   struct objfile *objfile = per_objfile->objfile;
@@ -561,6 +562,50 @@ dwarf_decode_macro_bytes (dwarf2_per_objfile *per_objfile,
           }
           break;
 
+	case DW_MACRO_define_strx:
+	case DW_MACRO_undef_strx:
+	  {
+	    unsigned int bytes_read;
+	    int line;
+	    int offset_index;
+	    const char* body;
+	    const gdb_byte* info_ptr;
+	    ULONGEST str_offset;
+
+	    line = read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+	    offset_index = read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+	    struct dwarf2_section_info str_offsets_section = per_objfile->per_bfd->str_offsets;
+	    str_offsets_section.read (objfile);
+	    info_ptr = (str_offsets_section.buffer
+			+ str_offsets_base
+			+ offset_index * offset_size);
+	    if (offset_size == 4)
+	      str_offset = bfd_get_32 (abfd, info_ptr);
+	    else
+	      str_offset = bfd_get_64 (abfd, info_ptr);
+	    body = per_objfile->per_bfd->str.read_string (objfile,
+							  str_offset,
+							  "DW_FORM_strx");
+	    
+	    if (! current_file)
+             {
+               /* DWARF violation as no main source is present.  */
+               complaint (_("debug info with no main source gives macro %s "
+                            "on line %d: %s"),
+                            macinfo_type == DW_MACRO_define_strx ? _("definition")
+                            : _("undefinition"), line, body);
+               break;
+             }
+
+	    if (macinfo_type == DW_MACRO_define_strx)
+	      parse_macro_definition (current_file, line, body);
+	    else
+	      macro_undef (current_file, line, body);
+	   }
+	   break;
+
         case DW_MACRO_start_file:
           {
             unsigned int bytes_read;
@@ -671,7 +716,7 @@ dwarf_decode_macro_bytes (dwarf2_per_objfile *per_objfile,
 					  new_mac_ptr, include_mac_end,
 					  current_file, lh, section,
 					  section_is_gnu, is_dwz, offset_size,
-					  include_hash);
+					  str_offsets_base, include_hash);
 
 		htab_remove_elt (include_hash, (void *) new_mac_ptr);
 	      }
@@ -712,7 +757,8 @@ dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
 		     buildsym_compunit *builder,
 		     const dwarf2_section_info *section,
 		     const struct line_header *lh, unsigned int offset_size,
-		     unsigned int offset, int section_is_gnu)
+		     unsigned int offset, ULONGEST str_offsets_base,
+		     int section_is_gnu)
 {
   bfd *abfd;
   const gdb_byte *mac_ptr, *mac_end;
@@ -814,6 +860,17 @@ dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
 	    mac_ptr += offset_size;
 	  }
 	  break;
+	case DW_MACRO_define_strx:
+	case DW_MACRO_undef_strx:
+	  {
+	    unsigned int bytes_read;
+
+	    read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+	    read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+	  }
+	  break;
 
 	case DW_MACRO_import:
 	case DW_MACRO_import_sup:
@@ -861,5 +918,5 @@ dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
   *slot = (void *) mac_ptr;
   dwarf_decode_macro_bytes (per_objfile, builder, abfd, mac_ptr, mac_end,
 			    current_file, lh, section, section_is_gnu, 0,
-			    offset_size, include_hash.get ());
+			    offset_size, str_offsets_base, include_hash.get ());
 }
diff --git a/gdb/dwarf2/macro.h b/gdb/dwarf2/macro.h
index d874068947..dc396e1b70 100644
--- a/gdb/dwarf2/macro.h
+++ b/gdb/dwarf2/macro.h
@@ -28,6 +28,7 @@ extern void dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
 				 const struct line_header *lh,
 				 unsigned int offset_size,
 				 unsigned int offset,
+				 ULONGEST str_offsets_base,
 				 int section_is_gnu);
 
 #endif /* GDB_DWARF2_MACRO_H */
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index e3073fe43c..a0e197c748 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -23353,8 +23353,10 @@ dwarf_decode_macros (struct dwarf2_cu *cu, unsigned int offset,
 
   buildsym_compunit *builder = cu->get_builder ();
 
+  ULONGEST str_offsets_base = *cu->str_offsets_base;
+
   dwarf_decode_macros (per_objfile, builder, section, lh,
-		       offset_size, offset, section_is_gnu);
+		       offset_size, offset, str_offsets_base, section_is_gnu);
 }
 
 /* Return the .debug_loc section to use for CU.
diff --git a/gdb/macrotab.c b/gdb/macrotab.c
index 63cd30148a..606f084bc9 100644
--- a/gdb/macrotab.c
+++ b/gdb/macrotab.c
@@ -507,7 +507,8 @@ struct macro_source_file *
 macro_lookup_inclusion (struct macro_source_file *source, const char *name)
 {
   /* Is SOURCE itself named NAME?  */
-  if (filename_cmp (name, source->filename) == 0)
+  if (filename_cmp (name, source->filename) == 0 ||
+      filename_cmp (basename (name), basename (source->filename)) == 0)
     return source;
 
   /* It's not us.  Try all our children, and return the lowest.  */
-- 
2.17.1

Re: [PATCH] DWARFv5: Handle DW_MACRO_define_strx and DW_MACRO_undef_strx macro entries.

[Simon Marchi]

git tells me this when applying:

  Applying: DWARFv5: Handle DW_MACRO_define_strx and DW_MACRO_undef_strx macro entries.
  .git/rebase-apply/patch:50: trailing whitespace.

  warning: 1 line adds whitespace errors.

please find and fix it.


On 2020-06-28 12:57 p.m., nitachra wrote:
> GDB is not able to print the macro values with -gdwarf-5 for clang
> generated binaries. Clang is emitting DW_MACRO_define_strx and
> DW_MACRO_undef_strx entries in .debug_macro section which are not
> supported in GDB. This patch handles them.
> 
> DW_MACRO_define_strx and DW_MACRO_undef_strx are added in DWARFv5.
> They have two operands. The first operand encodes the line number of
> the #define or #undef macro directive. The second operand identifies
> a string; it is represented using an unsigned LEB128 encoded value,
> which is interpreted as a zero-based index into an array of offsets
> in the .debug_str_offsets section. This is as per the section 6.3.2.1
> of Dwarf Debugging Information Format Version 5.
> 
> Test case used:
>  #define MAX_SIZE 10
> int main(void)
> {
>    int size = 0;
>    size = size + MAX_SIZE;
> 
>    printf("\n The value of size is [%d]\n",size);
> 
>    return 0;
> }
> 
> clang -gdwarf-5 -fdebug-macro  macro.c -o macro.out
> 
> Before the patch:
> 
> gdb -q  macro.out -ex "start" -ex "p MAX_SIZE"
> Reading symbols from macro.out...
> Temporary breakpoint 1 at 0x4004df: file macro.c, line 7.
> Starting program: /home/nitika/workspace/macro.out
> 
> Temporary breakpoint 1, main () at macro.c:7
> 7          int size = 0;
> No symbol "MAX_SIZE" in current context.
> 
> After the patch:
> 
> gdb -q  macro.out -ex "start" -ex "p MAX_SIZE"
> Reading symbols from macro.out...
> Temporary breakpoint 1 at 0x4004df: file macro.c, line 7.
> Starting program: /home/nitika/workspace/macro.out
> 
> Temporary breakpoint 1, main () at macro.c:7
> 7          int size = 0;
> $1 = 10
> 
> Tested by running the testsuite before and after the patch with
>  -gdwarf-5 and there is no increase in the number of test cases
> that fails. Used clang 11.0.0.

Hmm this is a bit misleading, as clang 11.0.0 is not released yet.  You must
have tested with a preview build.  Please indicate the exact version.

But thanks for specifying, because I only have clang 10 right now, and I didn't
see DW_MACRO_define_strx getting generated.

> 
> gdb/dwarf2/ChangeLog:

There is no gdb/dwarf2/ChangeLog file.  This will go in gdb/ChangeLog.

> *macro.c (dwarf_decode_macro_bytes): Handle DW_MACRO_define_strx
>  and DW_MACRO_undef_strx.
>  (dwarf_decode_macros): Likewise

Maybe it's just your mail client, but just to be sure, the format is:

<tab>*<space><filename>...

Wrapped lines are ligned with the *.

> *read.c (dwarf_decode_macros): Pass str_offsets_base in the parameters
>  which is the value of DW_AT_str_offsets_base.
> *macro.h (dwarf_decode_macros): Modify the definition to include
>  str_offsets_base.
> 
> gdb/ChangeLog:
> 
> *macrotab.c (macro_lookup_inclusion): In DWARF version 5 filename
> includes the full directory path.
> ---
>  gdb/dwarf2/macro.c | 63 +++++++++++++++++++++++++++++++++++++++++++---
>  gdb/dwarf2/macro.h |  1 +
>  gdb/dwarf2/read.c  |  4 ++-
>  gdb/macrotab.c     |  3 ++-
>  4 files changed, 66 insertions(+), 5 deletions(-)
> 
> diff --git a/gdb/dwarf2/macro.c b/gdb/dwarf2/macro.c
> index d047d806f8..2f5f3aa827 100644
> --- a/gdb/dwarf2/macro.c
> +++ b/gdb/dwarf2/macro.c
> @@ -427,6 +427,7 @@ dwarf_decode_macro_bytes (dwarf2_per_objfile *per_objfile,
>  			  const struct dwarf2_section_info *section,
>  			  int section_is_gnu, int section_is_dwz,
>  			  unsigned int offset_size,
> +			  ULONGEST str_offsets_base,
>  			  htab_t include_hash)
>  {
>    struct objfile *objfile = per_objfile->objfile;
> @@ -561,6 +562,50 @@ dwarf_decode_macro_bytes (dwarf2_per_objfile *per_objfile,
>            }
>            break;
>  
> +	case DW_MACRO_define_strx:
> +	case DW_MACRO_undef_strx:
> +	  {
> +	    unsigned int bytes_read;
> +	    int line;
> +	    int offset_index;
> +	    const char* body;
> +	    const gdb_byte* info_ptr;

Space before asterisk.

> +	    ULONGEST str_offset;

Declare all of these on first use (where applicable, doesn't apply
to `bytes_read` of course).

> +
> +	    line = read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
> +	    mac_ptr += bytes_read;
> +	    offset_index = read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
> +	    mac_ptr += bytes_read;
> +	    struct dwarf2_section_info str_offsets_section = per_objfile->per_bfd->str_offsets;

This line is too long.

When using a .dwo, the .debug_macro section is in the dwo (.debug_macro.dwo)?
If so, should we use the string offset and string sections from the dwo?

We don't have a testsuite board for DWARF5 + split-dwarf currently, I think
it would be useful.

> +	    str_offsets_section.read (objfile);
> +	    info_ptr = (str_offsets_section.buffer
> +			+ str_offsets_base
> +			+ offset_index * offset_size);
> +	    if (offset_size == 4)
> +	      str_offset = bfd_get_32 (abfd, info_ptr);
> +	    else
> +	      str_offset = bfd_get_64 (abfd, info_ptr);

Can we get some bound checking here, to avoid reading past the section buffer?

> +	    body = per_objfile->per_bfd->str.read_string (objfile,
> +							  str_offset,
> +							  "DW_FORM_strx");

The "DW_FORM_strx" is used for error reporting inside `read_string`.  I'm not
sure it's exact DW_FORM_strx here, because forms are used for attribute values,
which is not the case here.  Perhaps you could use "DW_MACRO_define_strx" and
"DW_MACRO_undef_strx", it would produce error messages like:

  DW_MACRO_define_strx used without %s section [in module %s]
  DW_MACRO_define_strx pointing outside of %s section [in module %s]

which I think make sense.

> +	    
> +	    if (! current_file)

current_file == nullptr

> +             {
> +               /* DWARF violation as no main source is present.  */
> +               complaint (_("debug info with no main source gives macro %s "
> +                            "on line %d: %s"),
> +                            macinfo_type == DW_MACRO_define_strx ? _("definition")
> +                            : _("undefinition"), line, body);
> +               break;

There are spaces that should be tabs here.

Simon

Re: [PATCH] DWARFv5: Handle DW_MACRO_define_strx and DW_MACRO_undef_strx macro entries.

[Tom Tromey]

>> +	    struct dwarf2_section_info str_offsets_section = per_objfile->per_bfd->str_offsets;

Simon> This line is too long.

It's also slightly bad to copy a section like this.  In weird cases I
think it can lead to it being read more than once.

We should probably delete operator= here, but that's a pain right now.
I think I have some patches toward this somewhere, but I haven't
finished them yet.  (Also, I think the DWP code does do this at the
moment.)

Better here to use a reference or a pointer.

Tom

Re: [PATCH] DWARFv5: Handle DW_MACRO_define_strx and DW_MACRO_undef_strx macro entries.

[Simon Marchi]

On 2020-07-11 6:54 p.m., Tom Tromey wrote:
>>> +	    struct dwarf2_section_info str_offsets_section = per_objfile->per_bfd->str_offsets;
> 
> Simon> This line is too long.
> 
> It's also slightly bad to copy a section like this.  In weird cases I
> think it can lead to it being read more than once.
> 
> We should probably delete operator= here, but that's a pain right now.
> I think I have some patches toward this somewhere, but I haven't
> finished them yet.  (Also, I think the DWP code does do this at the
> moment.)
> 
> Better here to use a reference or a pointer.
> 
> Tom
> 

Ah, I didn't notice that it wasn't a pointer, thanks.

Simon

[PATCH] DWARFv5: Handle DW_MACRO_define_strx and DW_MACRO_undef_strx macro entries.

[nitachra]

Hi Simon and Tom,

Thanks for the review. I've incorporated all of your review comments.
Please have a look.

>Hmm this is a bit misleading, as clang 11.0.0 is not released yet.  You must have tested with a preview build.  Please indicate the exact version.

>But thanks for specifying, because I only have clang 10 right now, and I didn't see DW_MACRO_define_strx getting generated.

clang --version gives me this-
clang version 11.0.0-++20200414064745+fc410138939-1~exp1~20200414165347.1623

>When using a .dwo, the .debug_macro section is in the dwo (.debug_macro.dwo)?
>If so, should we use the string offset and string sections from the dwo?

>We don't have a testsuite board for DWARF5 + split-dwarf currently, I think it would be useful.

Clang is not emitting DW_MACRO_define_strx and DW_MACRO_undef_strx in
the .debug_macro.dwo section as of now.

Regards,
Nitika

---
GDB is not able to print the macro values with -gdwarf-5 for clang
generated binaries. Clang is emitting DW_MACRO_define_strx and
DW_MACRO_undef_strx entries in .debug_macro section which are not
supported in GDB. This patch handles them.

DW_MACRO_define_strx and DW_MACRO_undef_strx are added in DWARFv5.
They have two operands. The first operand encodes the line number of
the #define or #undef macro directive. The second operand identifies
a string; it is represented using an unsigned LEB128 encoded value,
which is interpreted as a zero-based index into an array of offsets
in the .debug_str_offsets section. This is as per the section 6.3.2.1
of Dwarf Debugging Information Format Version 5.

Test case used:
 #define MAX_SIZE 10
int main(void)
{
   int size = 0;
   size = size + MAX_SIZE;

   printf("\n The value of size is [%d]\n",size);

   return 0;
}

clang -gdwarf-5 -fdebug-macro  macro.c -o macro.out

Before the patch:

gdb -q  macro.out -ex "start" -ex "p MAX_SIZE"
Reading symbols from macro.out...
Temporary breakpoint 1 at 0x4004df: file macro.c, line 7.
Starting program: /home/nitika/workspace/macro.out

Temporary breakpoint 1, main () at macro.c:7
7          int size = 0;
No symbol "MAX_SIZE" in current context.

After the patch:

gdb -q  macro.out -ex "start" -ex "p MAX_SIZE"
Reading symbols from macro.out...
Temporary breakpoint 1 at 0x4004df: file macro.c, line 7.
Starting program: /home/nitika/workspace/macro.out

Temporary breakpoint 1, main () at macro.c:7
7          int size = 0;
$1 = 10

Tested by running the testsuite before and after the patch with
 -gdwarf-5 and there is no increase in the number of test cases
that fails. Used clang 11.0.0.

gdb/ChangeLog:

	* dwarf2/macro.c (dwarf_decode_macro_bytes): Handle DW_MACRO_define_strx
	and DW_MACRO_undef_strx.
	(dwarf_decode_macros): Likewise
	* dwarf2/read.c (dwarf_decode_macros): Pass str_offsets_base in the parameters
	which is the value of DW_AT_str_offsets_base.
	* dwarf2/macro.h (dwarf_decode_macros): Modify the definition to include
	str_offsets_base.
	* macrotab.c (macro_lookup_inclusion): In DWARF version 5 filename
	includes the full directory path.
---
 gdb/dwarf2/macro.c | 69 ++++++++++++++++++++++++++++++++++++++++++++--
 gdb/dwarf2/macro.h |  1 +
 gdb/dwarf2/read.c  |  4 ++-
 gdb/macrotab.c     |  3 +-
 4 files changed, 72 insertions(+), 5 deletions(-)

diff --git a/gdb/dwarf2/macro.c b/gdb/dwarf2/macro.c
index d047d806f8..b48157a0d9 100644
--- a/gdb/dwarf2/macro.c
+++ b/gdb/dwarf2/macro.c
@@ -427,6 +427,7 @@ dwarf_decode_macro_bytes (dwarf2_per_objfile *per_objfile,
 			  const struct dwarf2_section_info *section,
 			  int section_is_gnu, int section_is_dwz,
 			  unsigned int offset_size,
+			  ULONGEST str_offsets_base,
 			  htab_t include_hash)
 {
   struct objfile *objfile = per_objfile->objfile;
@@ -561,6 +562,56 @@ dwarf_decode_macro_bytes (dwarf2_per_objfile *per_objfile,
           }
           break;
 
+	case DW_MACRO_define_strx:
+	case DW_MACRO_undef_strx:
+	  {
+	    unsigned int bytes_read;
+
+	    int line = read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+	    int offset_index = read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+	    struct dwarf2_section_info *str_offsets_section = (&per_objfile->per_bfd
+							       ->str_offsets);
+	    str_offsets_section->read (objfile);
+	    const gdb_byte *info_ptr = (str_offsets_section->buffer
+					+ str_offsets_base
+					+ offset_index * offset_size);
+
+	    const char *macinfo_str = (macinfo_type == DW_MACRO_define_strx ?
+				       "DW_MACRO_define_strx" : "DW_MACRO_undef_strx");
+
+	    if (str_offsets_base + offset_index * offset_size
+		>= str_offsets_section->size)
+	      complaint (_("%s pointing outside of .debug_str_offsets section "
+			   "[in module %s]"), macinfo_str, objfile_name (objfile));
+
+	    ULONGEST str_offset;
+	    if (offset_size == 4)
+	      str_offset = bfd_get_32 (abfd, info_ptr);
+	    else
+	      str_offset = bfd_get_64 (abfd, info_ptr);
+
+	    const char *body = per_objfile->per_bfd->str.read_string (objfile,
+								      str_offset,
+								      macinfo_str);
+	    if (current_file == nullptr)
+	      {
+		/* DWARF violation as no main source is present.  */
+		complaint (_("debug info with no main source gives macro %s "
+			     "on line %d: %s"),
+			     macinfo_type == DW_MACRO_define_strx ? _("definition")
+			     : _("undefinition"), line, body);
+		break;
+	      }
+
+	    if (macinfo_type == DW_MACRO_define_strx)
+	      parse_macro_definition (current_file, line, body);
+	    else
+	      macro_undef (current_file, line, body);
+	   }
+	   break;
+
         case DW_MACRO_start_file:
           {
             unsigned int bytes_read;
@@ -671,7 +722,7 @@ dwarf_decode_macro_bytes (dwarf2_per_objfile *per_objfile,
 					  new_mac_ptr, include_mac_end,
 					  current_file, lh, section,
 					  section_is_gnu, is_dwz, offset_size,
-					  include_hash);
+					  str_offsets_base, include_hash);
 
 		htab_remove_elt (include_hash, (void *) new_mac_ptr);
 	      }
@@ -712,7 +763,8 @@ dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
 		     buildsym_compunit *builder,
 		     const dwarf2_section_info *section,
 		     const struct line_header *lh, unsigned int offset_size,
-		     unsigned int offset, int section_is_gnu)
+		     unsigned int offset, ULONGEST str_offsets_base,
+		     int section_is_gnu)
 {
   bfd *abfd;
   const gdb_byte *mac_ptr, *mac_end;
@@ -814,6 +866,17 @@ dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
 	    mac_ptr += offset_size;
 	  }
 	  break;
+	case DW_MACRO_define_strx:
+	case DW_MACRO_undef_strx:
+	  {
+	    unsigned int bytes_read;
+
+	    read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+	    read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+	  }
+	  break;
 
 	case DW_MACRO_import:
 	case DW_MACRO_import_sup:
@@ -861,5 +924,5 @@ dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
   *slot = (void *) mac_ptr;
   dwarf_decode_macro_bytes (per_objfile, builder, abfd, mac_ptr, mac_end,
 			    current_file, lh, section, section_is_gnu, 0,
-			    offset_size, include_hash.get ());
+			    offset_size, str_offsets_base, include_hash.get ());
 }
diff --git a/gdb/dwarf2/macro.h b/gdb/dwarf2/macro.h
index d874068947..dc396e1b70 100644
--- a/gdb/dwarf2/macro.h
+++ b/gdb/dwarf2/macro.h
@@ -28,6 +28,7 @@ extern void dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
 				 const struct line_header *lh,
 				 unsigned int offset_size,
 				 unsigned int offset,
+				 ULONGEST str_offsets_base,
 				 int section_is_gnu);
 
 #endif /* GDB_DWARF2_MACRO_H */
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 558fad74f8..964872e8de 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -23350,8 +23350,10 @@ dwarf_decode_macros (struct dwarf2_cu *cu, unsigned int offset,
 
   buildsym_compunit *builder = cu->get_builder ();
 
+  ULONGEST str_offsets_base = *cu->str_offsets_base;
+
   dwarf_decode_macros (per_objfile, builder, section, lh,
-		       offset_size, offset, section_is_gnu);
+		       offset_size, offset, str_offsets_base, section_is_gnu);
 }
 
 /* Return the .debug_loc section to use for CU.
diff --git a/gdb/macrotab.c b/gdb/macrotab.c
index 9ada436eaf..4ffb2d67cb 100644
--- a/gdb/macrotab.c
+++ b/gdb/macrotab.c
@@ -507,7 +507,8 @@ struct macro_source_file *
 macro_lookup_inclusion (struct macro_source_file *source, const char *name)
 {
   /* Is SOURCE itself named NAME?  */
-  if (filename_cmp (name, source->filename) == 0)
+  if (filename_cmp (name, source->filename) == 0 ||
+      filename_cmp (basename (name), basename (source->filename)) == 0)
     return source;
 
   /* It's not us.  Try all our children, and return the lowest.  */
-- 
2.17.1

Re: [PATCH] DWARFv5: Handle DW_MACRO_define_strx and DW_MACRO_undef_strx macro entries.

[Simon Marchi]

On 2020-07-17 11:13 a.m., nitachra wrote:
> Hi Simon and Tom,
> 
> Thanks for the review. I've incorporated all of your review comments.
> Please have a look.
> 
>> Hmm this is a bit misleading, as clang 11.0.0 is not released yet.  You must have tested with a preview build.  Please indicate the exact version.
> 
>> But thanks for specifying, because I only have clang 10 right now, and I didn't see DW_MACRO_define_strx getting generated.
> 
> clang --version gives me this-
> clang version 11.0.0-++20200414064745+fc410138939-1~exp1~20200414165347.1623

Ok, I'm not very keen on basing our implementation on unstable compilers builds.  But I understand
this is all we have to work with right now.  Seeing that the clang 11 stable branch has been created,
do you think you could use the latest of that branch to test?  It is more likely to be close to the
behavior of the final clang 11 release.

>> When using a .dwo, the .debug_macro section is in the dwo (.debug_macro.dwo)?
>> If so, should we use the string offset and string sections from the dwo?
> 
>> We don't have a testsuite board for DWARF5 + split-dwarf currently, I think it would be useful.
> 
> Clang is not emitting DW_MACRO_define_strx and DW_MACRO_undef_strx in
> the .debug_macro.dwo section as of now.

Ok, but the day it will do so (or another compiler), do you think the current code is correct?

Simon

[PATCH] DWARFv5: Handle DW_MACRO_define_strx and DW_MACRO_undef_strx macro entries.

[nitachra]

Hi Simon,

I have made some changes to handle these entries when using .dwo file. Also,
tested this patch with the clang 11 stable build. Clang 11 is not
emitting DW_MACRO_define_strx and DW_MACRO_undef_strx with
-gsplit-dwarf. However, clang 12 is emitting them with -gsplit-dwarf.
Tested with -gsplit-dwarf using clang 12.

Regards,
Nitika

---
GDB is not able to print the macro values with -gdwarf-5 for clang
generated binaries. Clang is emitting DW_MACRO_define_strx and
DW_MACRO_undef_strx entries in .debug_macro section which are not
supported in GDB. This patch handles them.

DW_MACRO_define_strx and DW_MACRO_undef_strx are added in DWARFv5.
They have two operands. The first operand encodes the line number of
the #define or #undef macro directive. The second operand identifies
a string; it is represented using an unsigned LEB128 encoded value,
which is interpreted as a zero-based index into an array of offsets
in the .debug_str_offsets section. This is as per the section 6.3.2.1
of Dwarf Debugging Information Format Version 5.

Test case used:
 #define MAX_SIZE 10
int main(void)
{
   int size = 0;
   size = size + MAX_SIZE;

   printf("\n The value of size is [%d]\n",size);

   return 0;
}

clang -gdwarf-5 -fdebug-macro  macro.c -o macro.out

Before the patch:

gdb -q  macro.out -ex "start" -ex "p MAX_SIZE"
Reading symbols from macro.out...
Temporary breakpoint 1 at 0x4004df: file macro.c, line 7.
Starting program: /home/nitika/workspace/macro.out

Temporary breakpoint 1, main () at macro.c:7
7          int size = 0;
No symbol "MAX_SIZE" in current context.

After the patch:

gdb -q  macro.out -ex "start" -ex "p MAX_SIZE"
Reading symbols from macro.out...
Temporary breakpoint 1 at 0x4004df: file macro.c, line 7.
Starting program: /home/nitika/workspace/macro.out

Temporary breakpoint 1, main () at macro.c:7
7          int size = 0;
$1 = 10

Tested by running the testsuite before and after the patch with
 -gdwarf-5 and there is no increase in the number of test cases
that fails. Used clang 11.0.0.

gdb/ChangeLog:

	* dwarf2/macro.c (dwarf_decode_macro_bytes): Handle DW_MACRO_define_strx
	and DW_MACRO_undef_strx.
	(dwarf_decode_macros): Likewise
	* dwarf2/read.c (dwarf_decode_macros): Pass str_offsets_base in the parameters
	which is the value of DW_AT_str_offsets_base.
	* dwarf2/macro.h (dwarf_decode_macros): Modify the definition to include
	str_offsets_base.
	* macrotab.c (macro_lookup_inclusion): In DWARF version 5 filename
	includes the full directory path.
---
 gdb/dwarf2/macro.c | 72 ++++++++++++++++++++++++++++++++++++++++++++--
 gdb/dwarf2/macro.h |  3 ++
 gdb/dwarf2/read.c  | 21 +++++++++++++-
 gdb/macrotab.c     |  3 +-
 4 files changed, 94 insertions(+), 5 deletions(-)

diff --git a/gdb/dwarf2/macro.c b/gdb/dwarf2/macro.c
index d047d806f8..0fdc76a151 100644
--- a/gdb/dwarf2/macro.c
+++ b/gdb/dwarf2/macro.c
@@ -427,6 +427,9 @@ dwarf_decode_macro_bytes (dwarf2_per_objfile *per_objfile,
 			  const struct dwarf2_section_info *section,
 			  int section_is_gnu, int section_is_dwz,
 			  unsigned int offset_size,
+			  struct dwarf2_section_info *str_section,
+			  struct dwarf2_section_info *str_offsets_section,
+			  ULONGEST str_offsets_base,
 			  htab_t include_hash)
 {
   struct objfile *objfile = per_objfile->objfile;
@@ -561,6 +564,54 @@ dwarf_decode_macro_bytes (dwarf2_per_objfile *per_objfile,
           }
           break;
 
+	case DW_MACRO_define_strx:
+	case DW_MACRO_undef_strx:
+	  {
+	    unsigned int bytes_read;
+
+	    int line = read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+	    int offset_index = read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+
+	    str_offsets_section->read (objfile);
+	    const gdb_byte *info_ptr = (str_offsets_section->buffer
+					+ str_offsets_base
+					+ offset_index * offset_size);
+
+	    const char *macinfo_str = (macinfo_type == DW_MACRO_define_strx ?
+				       "DW_MACRO_define_strx" : "DW_MACRO_undef_strx");
+
+	    if (str_offsets_base + offset_index * offset_size
+		>= str_offsets_section->size)
+	      complaint (_("%s pointing outside of .debug_str_offsets section "
+			   "[in module %s]"), macinfo_str, objfile_name (objfile));
+
+	    ULONGEST str_offset;
+	    if (offset_size == 4)
+	      str_offset = bfd_get_32 (abfd, info_ptr);
+	    else
+	      str_offset = bfd_get_64 (abfd, info_ptr);
+
+	    const char *body = str_section->read_string (objfile, str_offset,
+							 macinfo_str);
+	    if (current_file == nullptr)
+	      {
+		/* DWARF violation as no main source is present.  */
+		complaint (_("debug info with no main source gives macro %s "
+			     "on line %d: %s"),
+			     macinfo_type == DW_MACRO_define_strx ? _("definition")
+			     : _("undefinition"), line, body);
+		break;
+	      }
+
+	    if (macinfo_type == DW_MACRO_define_strx)
+	      parse_macro_definition (current_file, line, body);
+	    else
+	      macro_undef (current_file, line, body);
+	   }
+	   break;
+
         case DW_MACRO_start_file:
           {
             unsigned int bytes_read;
@@ -671,7 +722,8 @@ dwarf_decode_macro_bytes (dwarf2_per_objfile *per_objfile,
 					  new_mac_ptr, include_mac_end,
 					  current_file, lh, section,
 					  section_is_gnu, is_dwz, offset_size,
-					  include_hash);
+					  str_section, str_offsets_section,
+					  str_offsets_base, include_hash);
 
 		htab_remove_elt (include_hash, (void *) new_mac_ptr);
 	      }
@@ -712,7 +764,9 @@ dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
 		     buildsym_compunit *builder,
 		     const dwarf2_section_info *section,
 		     const struct line_header *lh, unsigned int offset_size,
-		     unsigned int offset, int section_is_gnu)
+		     unsigned int offset, struct dwarf2_section_info *str_section,
+		     struct dwarf2_section_info *str_offsets_section,
+		     ULONGEST str_offsets_base, int section_is_gnu)
 {
   bfd *abfd;
   const gdb_byte *mac_ptr, *mac_end;
@@ -814,6 +868,17 @@ dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
 	    mac_ptr += offset_size;
 	  }
 	  break;
+	case DW_MACRO_define_strx:
+	case DW_MACRO_undef_strx:
+	  {
+	    unsigned int bytes_read;
+
+	    read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+	    read_unsigned_leb128 (abfd, mac_ptr, &bytes_read);
+	    mac_ptr += bytes_read;
+	  }
+	  break;
 
 	case DW_MACRO_import:
 	case DW_MACRO_import_sup:
@@ -861,5 +926,6 @@ dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
   *slot = (void *) mac_ptr;
   dwarf_decode_macro_bytes (per_objfile, builder, abfd, mac_ptr, mac_end,
 			    current_file, lh, section, section_is_gnu, 0,
-			    offset_size, include_hash.get ());
+			    offset_size, str_section, str_offsets_section,
+			    str_offsets_base, include_hash.get ());
 }
diff --git a/gdb/dwarf2/macro.h b/gdb/dwarf2/macro.h
index d874068947..0a7ac55fc0 100644
--- a/gdb/dwarf2/macro.h
+++ b/gdb/dwarf2/macro.h
@@ -28,6 +28,9 @@ extern void dwarf_decode_macros (dwarf2_per_objfile *per_objfile,
 				 const struct line_header *lh,
 				 unsigned int offset_size,
 				 unsigned int offset,
+				 dwarf2_section_info *str_section,
+				 dwarf2_section_info *str_offsets_section,
+				 ULONGEST str_offsets_base,
 				 int section_is_gnu);
 
 #endif /* GDB_DWARF2_MACRO_H */
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 558fad74f8..845adb0325 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -23350,8 +23350,27 @@ dwarf_decode_macros (struct dwarf2_cu *cu, unsigned int offset,
 
   buildsym_compunit *builder = cu->get_builder ();
 
+  struct dwarf2_section_info *str_offsets_section;
+  struct dwarf2_section_info *str_section;
+  ULONGEST str_offsets_base;
+
+  if (cu->dwo_unit != nullptr)
+    {
+      str_offsets_section = &cu->dwo_unit->dwo_file
+			       ->sections.str_offsets;
+      str_section = &cu->dwo_unit->dwo_file->sections.str;
+      str_offsets_base = cu->header.addr_size;
+    }
+  else
+    {
+      str_offsets_section = &per_objfile->per_bfd->str_offsets;
+      str_section = &per_objfile->per_bfd->str;
+      str_offsets_base = *cu->str_offsets_base;
+    }
+
   dwarf_decode_macros (per_objfile, builder, section, lh,
-		       offset_size, offset, section_is_gnu);
+		       offset_size, offset, str_section, str_offsets_section,
+		       str_offsets_base, section_is_gnu);
 }
 
 /* Return the .debug_loc section to use for CU.
diff --git a/gdb/macrotab.c b/gdb/macrotab.c
index 9ada436eaf..4ffb2d67cb 100644
--- a/gdb/macrotab.c
+++ b/gdb/macrotab.c
@@ -507,7 +507,8 @@ struct macro_source_file *
 macro_lookup_inclusion (struct macro_source_file *source, const char *name)
 {
   /* Is SOURCE itself named NAME?  */
-  if (filename_cmp (name, source->filename) == 0)
+  if (filename_cmp (name, source->filename) == 0 ||
+      filename_cmp (basename (name), basename (source->filename)) == 0)
     return source;
 
   /* It's not us.  Try all our children, and return the lowest.  */
-- 
2.17.1