libbacktrace testsuite fails with mold

[marxin]

Reproducer:

git clone https://github.com/ianlancetaylor/libbacktrace.git
cd libbacktrace
./configure
make check -j16

Note I used GCC 12.
then if I use mold for one of the tests:

$ gcc -funwind-tables -frandom-seed=ctesta_alloc -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wmissing-format-attribute -Wcast-qual -g -fuse-ld=mold -Wl,--compress-debug-sections=zlib-gabi -o ctesta_alloc ctesta_alloc-btest.o ctesta_alloc-testlib.o  ./.libs/libbacktrace_alloc.a  -fuse-ld=mold
$ ./ctesta_alloc
test1: [0]: missing file name or function name
FAIL: backtrace_full noinline
test2: [0]: missing file name or function name
FAIL: backtrace_full inline
test3: [0]: missing file name or function name
FAIL: backtrace_simple noinline
test4: [0]: missing file name or function name
FAIL: backtrace_simple inline
PASS: backtrace_syminfo variable

It's related to --compress-debug-sections=zlib-gabi as --compress-debug-sections=none is fine even with mold.

[marxin]

Apparently happens also with GCC 11:

$ gcc-11 -funwind-tables -frandom-seed=ctesta_alloc -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wmissing-format-attribute -Wcast-qual -g -Wl,--compress-debug-sections=zlib-gabi -o ctesta_alloc ctesta_alloc-btest.o ctesta_alloc-testlib.o  ./.libs/libbacktrace_alloc.a  -B /home/marxin/Programming/mold
$ readelf -p .comment ctesta_alloc

String dump of section '.comment':
  [     1]  mold 1.1.1 (9360267cc31db1e4f88412db90fa960c2728580a; compatible with GNU ld)
  [    4f]  GCC: (SUSE Linux) 11.2.1 20220316 [revision 6a1150d1524aeda3381b2171712e1a6611d441d6]
$ ./ctesta_alloc
test1: [0]: missing file name or function name
FAIL: backtrace_full noinline
test2: [0]: missing file name or function name
FAIL: backtrace_full inline
test3: [0]: missing file name or function name
FAIL: backtrace_simple noinline
test4: [0]: missing file name or function name
FAIL: backtrace_simple inline
PASS: backtrace_syminfo variable

[rui314]

I cannot reproduce the issue on my Ubuntu 20 machine. Can you pack the build directory with tar and share it with me, so that I can run the build command on my machine using your object files?

[marxin]

All right, apparently, so one needs to build all the objects with GCC 12!

Then:

$ gcc --version
gcc (GCC) 12.0.1 20220401 (experimental)
...
$ gcc -funwind-tables -frandom-seed=ctesta_alloc -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wmissing-format-attribute -Wcast-qual -g -Wl,--compress-debug-sections=zlib-gabi -o ctesta_alloc ctesta_alloc-btest.o ctesta_alloc-testlib.o  ./.libs/libbacktrace_alloc.a
$ ./ctesta_alloc
PASS: backtrace_full noinline
PASS: backtrace_full inline
PASS: backtrace_simple noinline
PASS: backtrace_simple inline
PASS: backtrace_syminfo variable
$ gcc -funwind-tables -frandom-seed=ctesta_alloc -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wmissing-format-attribute -Wcast-qual -g -Wl,--compress-debug-sections=zlib-gabi -o ctesta_alloc ctesta_alloc-btest.o ctesta_alloc-testlib.o  ./.libs/libbacktrace_alloc.a  -B /home/marxin/Programming/mold
$ ./ctesta_alloc
abbrev offset out of range
failed to read executable information
failed to read executable information
failed to read executable information
failed to read executable information
failed to read executable information
failed to read executable information
failed to read executable information
test1: not enough frames; got 0, expected at least 3
FAIL: backtrace_full noinline
failed to read executable information
failed to read executable information
failed to read executable information
failed to read executable information
failed to read executable information
FAIL: backtrace_full inline
failed to read executable information
failed to read executable information
failed to read executable information
failed to read executable information
test3: [0]: unexpected return value from backtrace_syminfo 0
failed to read executable information
test3: [1]: unexpected return value from backtrace_syminfo 0
failed to read executable information
test3: [2]: unexpected return value from backtrace_syminfo 0
FAIL: backtrace_simple noinline
failed to read executable information
FAIL: backtrace_simple inline
failed to read executable information
test5: unexpected return value from backtrace_syminfo 0
FAIL: backtrace_syminfo variable

Build dir (built with GCC 12): https://splichal.eu/tmp/libbacktrace.tar.bz2

[rui314]

Thanks for the info. It looks like it is a bug in libbacktrace and not in mold. I'll send a PR to libbacktrace to fix the issue.

[rui314]

It took me a few hours to find the cause of the issue, but it looks like with the above fix, libbacktrace's tests are now green when built with mold.

[ianlancetaylor]

Thanks for the bug report and fix. The libbacktrace repo and GCC tip have been updated with @rui314 's patch.