scripts: Document existing problems with the symbolizer build script.

[vitalybuka]

Thank you!

[Enna1]

Hi @vitalybuka @pcc
is there any progress about this problem? Is symbolizer.o can be buildable with a regular cmake rule possible now? Thanks!

[vitalybuka]

We didn't look into that.
Are you interested in this feature? I expect almost none other but Google internally uses this approach.

[Enna1]

Thanks for your reply!
Internal symbolizer is a very useful feature, which lets us symbolize sanitizer error report without the dependency of external symbolizer tool.
I have tested the build_symbolizer.sh approach in my local environment, we will try to deploy the build_symbolizer.sh approach to our sanitizer buildbot.
The cmake approach may be more compilcated according to https://bugs.llvm.org/show_bug.cgi?id=30750, I will give it a try.

compiler-rt/trunk/lib/sanitizer_common/symbolizer/scripts/build_symbolizer.sh

 # avoiding dependencies on any program symbols. The only acceptable dependencies
 # are libc and __sanitizer::internal_* from sanitizer runtime.
 #
 # Symbols exported by the object file will be used by Sanitizer runtime
 # libraries to symbolize code/data in-process.
 #
 # The script will modify the output directory which is given as the first
 # argument to the script.
+#
+# FIXME: We should really be using a simpler approach to building this object
+# file, and it should be available as a regular cmake rule. Conceptually, we
+# want to be doing "ld -r" followed by "objcopy -G" to create a relocatable
+# object file with only our entry points exposed. However, this does not work at
+# present, see PR30750.
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
 SRC_DIR=$(readlink -f $SCRIPT_DIR/..)
 TARGE_DIR=$(readlink -f $1)
 
 LLVM_SRC="${LLVM_SRC:-$SCRIPT_DIR/../../../../../..}"
 LLVM_SRC=$(readlink -f $LLVM_SRC)