https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112858
--- Comment #5 from Thomas Schwinge <tschwinge at gcc dot gnu.org> ---
(I did see that the '__cxa_thread_atexit_impl' issue has been resolved
differently, but there is a genuine GCC/nvptx issue here.)
(In reply to myself from comment #1)
> Indeed in 'build-gcc/nvptx-none/libstdc++-v3/libsupc++/atexit_thread.o' I
> see:
>
> // BEGIN GLOBAL FUNCTION DECL: __cxa_thread_atexit_impl
> .extern .func (.param .u32 %value_out) __cxa_thread_atexit_impl (.param
> .u64 %in_ar0, .param .u64 %in_ar1, .param .u64 %in_ar2);
>
> That is, '.extern' instead of '.weak' linking directive, huh.
That one indeed is a GCC/nvptx back end issue. A fix might look similar to the
following:
--- gcc/config/nvptx/nvptx.cc
+++ gcc/config/nvptx/nvptx.cc
@@ -1001,10 +1001,11 @@ write_fn_proto_1 (std::stringstream &s, bool
is_defn,
const char *name, const_tree decl, bool force_public)
{
- if (lookup_attribute ("alias", DECL_ATTRIBUTES (decl)) == NULL)
+ if (lookup_attribute ("alias", DECL_ATTRIBUTES (decl)) == NULL
+ && !DECL_WEAK (decl))
write_fn_marker (s, is_defn, TREE_PUBLIC (decl) || force_public,
name);
/* PTX declaration. */
if (DECL_EXTERNAL (decl))
- s << ".extern ";
+ s << (DECL_WEAK (decl) ? ".weak " : ".extern ");
else if (TREE_PUBLIC (decl) || force_public)
s << (DECL_WEAK (decl) ? ".weak " : ".visible ");
> ..., but still doing the NULL check: [...]
..., and that check ('if (__cxa_thread_atexit_impl)') then fails to assemble,
and thus the build (!) fails:
ptxas fatal : Cannot take address of function '__cxa_thread_atexit_impl'
Thus, more smarts are needed to make "weak, undefined" work. (May be able to
fix this up in the linker, assuming seeing the whole program; similar to
PR105018 "[nvptx] Need better alias support" ideas?) (For reference, "weak,
defined" does not run into this problem.)
