On Mon, 25 Jan 2021, Jakub Jelinek wrote:
> Hi!
>
> binutils since https://sourceware.org/bugzilla/show_bug.cgi?id=25612
> changes from March last year until the
> https://sourceware.org/pipermail/binutils/2020-August/112684.html
> fix in early August emits incorrect .debug_info when assembling files
> with --gdwarf-5. Instead of emitting proper DWARF 5 .debug_info header,
> it emits DWARF 4 .debug_info header with 5 as the dwarf version instead of
> 4. This results e.g. in libgcc.a (morestack.o) having garbage in its
> .debug_info sections and e.g. libbacktrace during pretty much all libgo
> tests fails miserably.
>
> The following patch adds a workaround for that, don't set
> HAVE_AS_GDWARF_5_DEBUG_FLAG if readelf can't read the .debug_info back.
>
> Built tested on x86_64-linux against both binutils 2.35 (buggy ones) and
> latest binutils trunk, the former with the patch now has DWARF 3
> .debug_line and DWARF 2 .debug_info in morestack.o, while the latter
> as before correct DWARF 5 .debug_line and .debug_info.
>
> Ok for trunk?
OK.
Richard.
> 2021-01-25 Jakub Jelinek <ja...@redhat.com>
>
> PR debug/98811
> * configure.ac (HAVE_AS_GDWARF_5_DEBUG_FLAG): Only define if
> readelf -wi is able to read the emitted .debug_info back.
> * configure: Regenerated.
>
> --- gcc/configure.ac.jj 2021-01-25 12:35:11.034835330 +0100
> +++ gcc/configure.ac 2021-01-25 13:04:10.002980861 +0100
> @@ -5416,8 +5416,12 @@ if test x"$insn" != x; then
>
> gcc_GAS_CHECK_FEATURE([--gdwarf-5 option],
> gcc_cv_as_gdwarf_5_flag,
> - [elf,2,36,0], [--gdwarf-5], [$insn],,
> - [AC_DEFINE(HAVE_AS_GDWARF_5_DEBUG_FLAG, 1,
> + [elf,2,36,0], [--gdwarf-5], [$insn],
> + [if test x$gcc_cv_readelf != x \
> + && $gcc_cv_readelf -wi conftest.o 2>&1 \
> + | grep DW_TAG_compile_unit > /dev/null 2>&1; then
> + gcc_cv_as_gdwarf_5_flag=yes;
> + fi],[AC_DEFINE(HAVE_AS_GDWARF_5_DEBUG_FLAG, 1,
> [Define if your assembler supports the --gdwarf-5 option.])])
>
> dwarf4_debug_info_size=0x46
> --- gcc/configure.jj 2021-01-25 12:35:11.012835581 +0100
> +++ gcc/configure 2021-01-25 13:04:14.982924030 +0100
> @@ -29075,7 +29075,11 @@ fi
> $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> test $ac_status = 0; }; }
> then
> - gcc_cv_as_gdwarf_5_flag=yes
> + if test x$gcc_cv_readelf != x \
> + && $gcc_cv_readelf -wi conftest.o 2>&1 \
> + | grep DW_TAG_compile_unit > /dev/null 2>&1; then
> + gcc_cv_as_gdwarf_5_flag=yes;
> + fi
> else
> echo "configure: failed program was" >&5
> cat conftest.s >&5
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
