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[gdb/symtab] Handle struct decl with DW_AT_signature 

Consider a test-case with sources 36.c:
...
struct s { int i; };
extern void f (void);
int main (void) {
  struct s a;
  f ();
  return 0;
}
...
and 36b.c:
...
struct s { int j; };
void f (void) {
  struct s b;
}
...
compiled like this:
...
$ gcc 36.c 36b.c -g
...

It contains DWARF like this:
...
 <0><d2>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <d8>   DW_AT_name        : 36.c
 <1><f4>: Abbrev Number: 2 (DW_TAG_structure_type)
    <f5>   DW_AT_name        : s
 <2><fe>: Abbrev Number: 3 (DW_TAG_member)
    <ff>   DW_AT_name        : i
 <1><110>: Abbrev Number: 5 (DW_TAG_subprogram)
    <111>   DW_AT_name        : main
 <2><12d>: Abbrev Number: 6 (DW_TAG_variable)
    <12e>   DW_AT_name        : a
    <132>   DW_AT_type        : <0xf4>
 <0><146>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <14c>   DW_AT_name        : 36b.c
 <1><168>: Abbrev Number: 2 (DW_TAG_structure_type)
    <169>   DW_AT_name        : s
 <2><172>: Abbrev Number: 3 (DW_TAG_member)
    <173>   DW_AT_name        : j
 <1><184>: Abbrev Number: 5 (DW_TAG_subprogram)
    <185>   DW_AT_name        : f
 <2><19b>: Abbrev Number: 6 (DW_TAG_variable)
    <19c>   DW_AT_name        : b
    <1a0>   DW_AT_type        : <0x168>
...

And when printing "struct s", we get first a random one (with int j), and then
context-specific ones (with int i in main, and int j in f):
...
$ gdb -batch a.out \
  -ex "ptype struct s" \
  -ex start \
  -ex "ptype struct s" \
  -ex "break f" -ex continue \
  -ex "ptype struct s" \
  | grep "int [ij];"
    int j;
    int i;
    int j;
...
Same for -readnow.

However, if we use -fdebug-types-section:
...
$ gcc 36.c 36b.c -g -fdebug-types-section
...
we get:
...
$ gdb ... | grep "int [ij];"
    int j;
    int i;
    int i;
$ gdb -readnow ... | grep "int [ij];"
    int j;
    int j;
    int j;
...

This is due to the fact that both "struct s" DIEs have been moved to the
.debug_types section:
...
  Compilation Unit @ offset 0x0:
   Signature:     0xfd1462823bb6f7b7
 <0><17>: Abbrev Number: 1 (DW_TAG_type_unit)
 <1><1d>: Abbrev Number: 2 (DW_TAG_structure_type)
    <1e>   DW_AT_name        : s
 <2><27>: Abbrev Number: 3 (DW_TAG_member)
    <28>   DW_AT_name        : i
  Compilation Unit @ offset 0x3a:
   Signature:     0x534310fbefba324d
 <0><51>: Abbrev Number: 1 (DW_TAG_type_unit)
 <1><57>: Abbrev Number: 2 (DW_TAG_structure_type)
    <58>   DW_AT_name        : s
 <2><61>: Abbrev Number: 3 (DW_TAG_member)
    <62>   DW_AT_name        : j
...
and there's no longer a "struct s" DIE in the 36.c and
and 36b.c CUs to specify which "struct s" belongs in the CU.  This is gcc
PR90232.

However, using a tentative patch for gcc that adds these DIEs (according to
DWARF standard: If the complete declaration of a type has been placed in a
separate type unit, an incomplete declaration of that type in the compilation
unit may provide the unique 64-bit signature of the type using a
DW_AT_signature attribute):
...
  <0><d2>: Abbrev Number: 5 (DW_TAG_compile_unit)
     <d8>   DW_AT_name        : 36.c
+ <1><f4>: Abbrev Number: 6 (DW_TAG_structure_type)
+    <f5>   DW_AT_name        : s
+    <f7>   DW_AT_signature   : signature: 0xfd1462823bb6f7b7
+    <ff>   DW_AT_declaration : 1
  <0><13c>: Abbrev Number: 5 (DW_TAG_compile_unit)
     <142>   DW_AT_name        : 36b.c
+ <1><15e>: Abbrev Number: 6 (DW_TAG_structure_type)
+    <15f>   DW_AT_name        : s
+    <161>   DW_AT_signature   : signature: 0x534310fbefba324d
+    <169>   DW_AT_declaration : 1
...
still does not help, because they're declarations, so new_symbol is not called
for them in process_structure_scope.

Fix this by calling new_symbol for these decls.

Build and tested on x86_64-linux.

Also tested with target board enabling by default -fdebug-types-section
-gdwarf-4, and with gcc with aforementioned tentative patch.  In this
configuration, the patch reduces number of FAILs from 2888 to 238.

gdb/ChangeLog:

2020-04-28  Tom de Vries  <tdevries@suse.de>

	* dwarf2/read.c (process_structure_scope): Add symbol for struct decl
	with DW_AT_signature.

gdb/testsuite/ChangeLog:

2020-04-28  Tom de Vries  <tdevries@suse.de>

	* gdb.dwarf2/main-foo.c: New test.
	* gdb.dwarf2/struct-with-sig.exp: New file.
This commit is contained in:
Tom de Vries 2020-04-28 06:12:35 +02:00
parent 30b57e1bea
commit 15cd93d05e
5 changed files with 187 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
gdb/ChangeLog
View File

@ -1,3 +1,8 @@
2020-04-28 Tom de Vries <tdevries@suse.de>
* dwarf2/read.c (process_structure_scope): Add symbol for struct decl
with DW_AT_signature.
2020-04-27 Simon Marchi <simon.marchi@efficios.com>
* configure.ac: Remove check for fs_base/gs_base in

3
gdb/dwarf2/read.c
View File

@ -15748,7 +15748,8 @@ process_structure_scope (struct die_info *die, struct dwarf2_cu *cu)
these DIEs are identified by the fact that they have no byte_size
attribute, and a declaration attribute. */
if (dwarf2_attr (die, DW_AT_byte_size, cu) != NULL
|| !die_is_declaration (die, cu))
|| !die_is_declaration (die, cu)
|| dwarf2_attr (die, DW_AT_signature, cu) != NULL)
{
struct symbol *sym = new_symbol (die, type, cu);

5
gdb/testsuite/ChangeLog
View File

@ -1,3 +1,8 @@
2020-04-28 Tom de Vries <tdevries@suse.de>
* gdb.dwarf2/main-foo.c: New test.
* gdb.dwarf2/struct-with-sig.exp: New file.
2020-04-25 Tom de Vries <tdevries@suse.de>
* boards/debug-types.exp: New file.

34
gdb/testsuite/gdb.dwarf2/main-foo.c Normal file
View File

@ -0,0 +1,34 @@
/* This testcase is part of GDB, the GNU debugger.
Copyright 2020 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/>. */
/* Dummy foo function. */
void
foo (void)
{
asm ("foo_label: .globl foo_label");
}
/* Dummy main function. */
int
main()
{
asm ("main_label: .globl main_label");
foo ();
return 0;
}

141
gdb/testsuite/gdb.dwarf2/struct-with-sig.exp Normal file
View File

@ -0,0 +1,141 @@
# Copyright 2020 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 dwarf.exp
# This test can only be run on targets which support DWARF-2 and use gas.
if {![dwarf2_support]} {
return 0
}
standard_testfile main-foo.c .S
# Make some DWARF for the test.
set asm_file [standard_output_file $srcfile2]
Dwarf::assemble $asm_file {
global srcdir subdir srcfile
lassign [function_range main ${srcdir}/${subdir}/${srcfile}] \
main_start main_length
lassign [function_range foo ${srcdir}/${subdir}/${srcfile}] \
foo_start foo_length
cu {} {
compile_unit {
{DW_AT_language @DW_LANG_C}
{DW_AT_name main.c}
} {
structure_type {
{name s}
{signature 0x0000000000000001 ref_sig8}
{declaration 1 flag}
}
DW_TAG_subprogram {
{name "main"}
{low_pc $main_start addr}
{high_pc "$main_start + $main_length" addr}
}
}
}
cu {} {
compile_unit {
{DW_AT_language @DW_LANG_C}
{DW_AT_name foo.c}
} {
structure_type {
{name s}
{signature 0x0000000000000002 ref_sig8}
{declaration 1 flag}
}
DW_TAG_subprogram {
{name "foo"}
{low_pc $foo_start addr}
{high_pc "$foo_start + $foo_length" addr}
}
}
}
tu {} 0x0000000000000001 the_type_i {
type_unit {} {
declare_labels int_type
the_type_i: structure_type {
{name s}
{byte_size 4 sdata}
} {
member {
{name i}
{type :$int_type}
}
}
int_type: base_type {
{name int}
{encoding @DW_ATE_signed}
{byte_size 4 sdata}
}
}
}
tu {} 0x0000000000000002 the_type_j {
type_unit {} {
declare_labels int_type
the_type_j: structure_type {
{name s}
{byte_size 4 sdata}
} {
member {
{name j}
{type :$int_type}
}
}
int_type: base_type {
{name int}
{encoding @DW_ATE_signed}
{byte_size 4 sdata}
}
}
}
}
if { [prepare_for_testing "failed to prepare" ${testfile} \
[list $srcfile $asm_file] {nodebug}] } {
return -1
}
set struct_s_i_re \
[multi_line \
"type = struct s {" \
" int i;" \
"}"]
set struct_s_j_re \
[multi_line \
"type = struct s {" \
" int j;" \
"}"]
if ![runto_main] {
return -1
}
gdb_test "ptype struct s" $struct_s_i_re \
"struct s with int i"
gdb_breakpoint "foo"
gdb_continue_to_breakpoint "foo"
gdb_test "ptype struct s" $struct_s_j_re \
"struct s with int j"