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binutils-gdb/gdb/testsuite/gdb.base/symbol-alias2.c

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Handle function aliases better (PR gdb/19487, errno printing) (Ref: https://sourceware.org/ml/gdb/2017-06/msg00048.html) This patch improves GDB support for function aliases defined with __attribute__ alias. For example, in the test added by this commit, there is no reference to "func_alias" in the debug info at all, only to "func"'s definition: $ nm ./testsuite/outputs/gdb.base/symbol-alias/symbol-alias | grep " func" 00000000004005ae t func 00000000004005ae T func_alias $ readelf -w ./testsuite/outputs/gdb.base/symbol-alias/symbol-alias | grep func -B 1 -A 8 <1><db>: Abbrev Number: 5 (DW_TAG_subprogram) <dc> DW_AT_name : (indirect string, offset: 0x111): func <e0> DW_AT_decl_file : 1 <e1> DW_AT_decl_line : 27 <e2> DW_AT_prototyped : 1 <e2> DW_AT_type : <0xf8> <e6> DW_AT_low_pc : 0x4005ae <ee> DW_AT_high_pc : 0xb <f6> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa) <f8> DW_AT_GNU_all_call_sites: 1 So all GDB knows about "func_alias" is from the minsym (elf symbol): (gdb) p func_alias $1 = {<text variable, no debug info>} 0x4005ae <func> (gdb) ptype func_alias type = int () (gdb) p func $2 = {struct S *(void)} 0x4005ae <func> (gdb) ptype func type = struct S { int field1; int field2; } *(void) The result is that calling func_alias from the command line produces incorrect results. This is similar (though not exactly the same) to the glibc errno/__errno_location/__GI___errno_location situation. On glibc, errno is defined like this: extern int *__errno_location (void); #define errno (*__errno_location ()) with __GI___errno_location being an internal alias for __errno_location. On my system's libc (F23), I do see debug info for __errno_location, in the form of name vs linkage name: <1><95a5>: Abbrev Number: 18 (DW_TAG_subprogram) <95a6> DW_AT_external : 1 <95a6> DW_AT_name : (indirect string, offset: 0x2c26): __errno_location <95aa> DW_AT_decl_file : 1 <95ab> DW_AT_decl_line : 24 <95ac> DW_AT_linkage_name: (indirect string, offset: 0x2c21): __GI___errno_location <95b0> DW_AT_prototyped : 1 <95b0> DW_AT_type : <0x9206> <95b4> DW_AT_low_pc : 0x20f40 <95bc> DW_AT_high_pc : 0x11 <95c4> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa) <95c6> DW_AT_GNU_all_call_sites: 1 however that doesn't matter in practice, because GDB doesn't record demangled names anyway, and so we end up with the exact same situation covered by the testcase. So the fix is to make the expression parser find a debug symbol for the same address as the just-found minsym, when a lookup by name didn't find a debug symbol by name. We now get: (gdb) p func_alias $1 = {struct S *(void)} 0x4005ae <func> (gdb) p __errno_location $2 = {int *(void)} 0x7ffff6e92830 <__errno_location> I've made the test exercise variable aliases too, for completeness. Those already work correctly, because unlike for function aliases, GCC emits debug information for variable aliases. Tested on GNU/Linux. gdb/ChangeLog: 2017-08-21 Pedro Alves <palves@redhat.com> PR gdb/19487 * c-exp.y (variable production): Handle function aliases. * minsyms.c (msymbol_is_text): New function. * minsyms.h (msymbol_is_text): Declare. * symtab.c (find_function_alias_target): New function. * symtab.h (find_function_alias_target): Declare. gdb/testsuite/ChangeLog: 2017-08-21 Pedro Alves <palves@redhat.com> PR gdb/19487 * gdb.base/symbol-alias.c: New. * gdb.base/symbol-alias2.c: New. * gdb.base/symbol-alias.exp: New.
2017-08-21 12:34:32 +02:00
/* This test is part of GDB, the GNU debugger.
Copyright 2017 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 S
{
int field1;
int field2;
};
struct S g_var_s = { 1, 2 };
static struct S *
func (void)
{
return &g_var_s;
}
struct S *func_alias (void) __attribute__ ((alias ("func")));
extern struct S g_var_s_alias __attribute__ ((alias ("g_var_s")));