clang: support __attribute__((__symver__("...")))

[bnoordhuis]

clang does not seem to support gcc's __symver__ attribute (also spelled symver). It would be nice if it did.

gcc documentation: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes (sorry, I can't seem to link to a specific entry - it's about 4/5th down)

My workaround looks like this:

#ifdef __clang__
__asm__(".symver foo,foo@@V1.2.3");
#else
__attribute__((__symver__("foo@@V1.2.3")))
#endif
void foo(void) {}

Other people/projects seem to hit this as well, ex. https://github.com/OpenMandrivaAssociation/kernel-rc/blob/087b62e4c6c036c4cf79558891b6851a67b2f684/linux-5.16-clang-no-attribute-symver.patch

[llvmbot]

@llvm/issue-subscribers-clang-frontend