-fdata-sections decides whether global variables go into different sections.
This is orthogonal to whether we place their metadata (`.data` or `asan_globals`) into different sections.
With -fno-data-sections, `-fsanitize-address-globals-dead-stripping` can still:
* deduplicate COMDAT `asan.module_ctor` and `asan.module_dtor`
* (with ld --gc-sections): for a data section (e.g. `.data`), if all global variables defined relative to it are unreferenced, discard them and associated `asan_globals` sections (rare but no need to exclude this case)
Similar to c7b90947bd0179d914fea56b52be545c8f60f20a for PE/COFF.
Reviewed By: #sanitizers, kstoimenov, vitalybuka
Differential Revision: https://reviews.llvm.org/D120394
This feature is subtly broken when the linker is gold 2.26 or
earlier. See the following bug for details:
https://sourceware.org/bugzilla/show_bug.cgi?id=19002
Since the decision needs to be made at compilation time, we can not
test the linker version. The flag is off by default on ELF targets,
and on otherwise.
llvm-svn: 302591
This change restores pre-r301225 behavior, where linker GC compatible global
instrumentation was used on COFF targets disregarding -f(no-)data-sections and/or
/Gw flags.
This instrumentation puts each global in a COMDAT with an ASan descriptor for that global.
It effectively enables -fdata-sections, but limits it to ASan-instrumented globals.
llvm-svn: 301374
