Paul Eggert wrote:
> If I understand things correctly a similar problem was also on FreeBSD
> with PIE and the bug wasn't fixed until November of last year:
>
> https://github.com/llvm/llvm-project/commit/7440e4ed85aa992718d4b5ccd1c97724bc3bdd2c
This issue does not affect the Gnulib 'stack-trace' module, because
we link only to GCC's sanitizer library, not to clang's sanitizer library.
But looking into the situation on FreeBSD, it appears that the 'stack-trace'
module could be enhanced with clang-specific approaches:
(A) Use the fact that clang's internal libraries
libclang_rt.{asan,msan,tsan,ubsan_standalone}.a
define the symbol __sanitizer_print_stack_trace, like GCC's libasan does.
This would mean that m4/stack-trace.m4 would add to $CC and $CXX the
option '-fsanitize=return' [1]. This appears to be the cheapest way to
include __sanitizer_print_stack_trace in the executable.
However, there are several drawbacks:
* An autoconf macro should not modify the value of CC (or CFLAGS).
* Programs compiled this way link to 6 additional shared libraries:
libthr.so.3
librt.so.1
libm.so.5
libexecinfo.so.1
libgcc_s.so.1
libelf.so.2
* The behaviour becomes dependent on some environment variables.
* The approach does not work if $CC already contains the option
'-fsanitize-minimal-runtime'.
(B) Do what __sanitizer_print_stack_trace does, namely invoke the program
'llvm-symbolizer' [2]. This program is installed by default in /usr/bin
in FreeBSD ≥ 13.
There are several drawbacks here as well:
* Gnulib would need extra code to get the addresses from libexecinfo,
determine VMA boundaries (using /proc, I guess), then invoke
llvm-symbolizer as a subprocess.
* The approach does not work if llvm-symbolizer is not found in $PATH.
* Extra command-line options are needed on macOS, due to .dSYM.
The existing first-choice approach (libbacktrace) is better than either of
(A) or (B). Therefore I see no reason for implementing (A) or (B).
Bruno
[1]
https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html#stack-traces-and-report-symbolization
[2] https://llvm.org/docs/CommandGuide/llvm-symbolizer.html
