On Wed, 19 Mar 2025 at 14:21, Marek Polacek <pola...@redhat.com> wrote:
>
> On Wed, Mar 19, 2025 at 12:38:31PM +0100, Thomas Schwinge wrote:
> > In 2001 Subversion r40924 (Git commit
> > 52a11cbfcf0cfb32628b6953588b6af4037ac0b6)
> > "IA-64 ABI Exception Handling", '__cxa_bad_cast' changed from 'void *' to
> > 'void' return type:
> >
> > --- libstdc++-v3/libsupc++/exception_support.cc
> > +++ /dev/null
> > @@ -1,388 +0,0 @@
> > -[...]
> > -// Helpers for rtti. Although these don't return, we give them return
> > types so
> > -// that the type system is not broken.
> > -extern "C" void *
> > -__cxa_bad_cast ()
> > -{
> > - [...]
> > -}
> > -[...]
> >
> > --- /dev/null
> > +++ libstdc++-v3/libsupc++/unwind-cxx.h
> > @@ -0,0 +1,163 @@
> > +[...]
> > +extern "C" void __cxa_bad_cast ();
> > +[...]
> >
> > --- /dev/null
> > +++ libstdc++-v3/libsupc++/eh_aux_runtime.cc
> > @@ -0,0 +1,56 @@
> > +[...]
> > +extern "C" void
> > +__cxa_bad_cast ()
> > +{
> > + [...]
> > +}
> > +[...]
> >
> > The implicit prototype in the C++ front end however wasn't likewise
> > adjusted,
> > and so for nvptx we generate code for 'void *' return type:
> >
> > // BEGIN GLOBAL FUNCTION DECL: __cxa_bad_cast
> > .extern .func (.param .u64 %value_out) __cxa_bad_cast;
> >
> > {
> > .param .u64 %value_in;
> > call (%value_in),__cxa_bad_cast;
> > trap;
> > // (noreturn)
> > exit;
> > // (noreturn)
> > ld.param.u64 %r30,[%value_in];
> > }
> >
> > ..., which is in conflict with the library code with 'void' return type:
> >
> > // BEGIN GLOBAL FUNCTION DECL: __cxa_bad_cast
> > .visible .func __cxa_bad_cast;
> >
> > // BEGIN GLOBAL FUNCTION DEF: __cxa_bad_cast
> > .visible .func __cxa_bad_cast
> > {
> > [...]
> > }
> >
> > ..., and we thus get execution test FAIL for 'g++.dg/rtti/dyncast2.C':
> >
> > error : Prototype doesn't match for '__cxa_bad_cast' in 'input file 7
> > at offset 51437', first defined in 'input file 7 at offset 51437'
> > nvptx-run: cuLinkAddData failed: device kernel image is invalid
> > (CUDA_ERROR_INVALID_SOURCE, 300)
> >
> > With this patched, we get the expected:
> >
> > // BEGIN GLOBAL FUNCTION DECL: __cxa_bad_cast
> > -.extern .func (.param .u64 %value_out) __cxa_bad_cast;
> > +.extern .func __cxa_bad_cast;
> >
> > {
> > -.param .u64 %value_in;
> > -call (%value_in),__cxa_bad_cast;
> > +call __cxa_bad_cast;
> > trap;
> > // (noreturn)
> > exit;
> > // (noreturn)
> > -ld.param.u64 %r30,[%value_in];
> > }
> >
> > ..., and execution test PASS.
> >
> > gcc/cp/
> > * rtti.cc (throw_bad_cast): Adjust implicit '__cxa_bad_cast'
> > prototype to reality.
> > ---
> > gcc/cp/rtti.cc | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/gcc/cp/rtti.cc b/gcc/cp/rtti.cc
> > index dcf84f17163..a10fa383f79 100644
> > --- a/gcc/cp/rtti.cc
> > +++ b/gcc/cp/rtti.cc
> > @@ -198,7 +198,7 @@ throw_bad_cast (void)
> > fn = get_global_binding (name);
> > if (!fn)
> > fn = push_throw_library_fn
> > - (name, build_function_type_list (ptr_type_node, NULL_TREE));
> > + (name, build_function_type_list (void_type_node, NULL_TREE));
> > }
> >
> > return build_cxx_call (fn, 0, NULL, tf_warning_or_error);
>
> LGTM, matches what I see in abi-eh.html from the itanium-cxx-abi.
>
> The comment above mentions libstdc++/exception.cc but I don't see that
> file.
I think that was removed in 2001 by r39445 :-)
