Hi!
On 2025-03-19T14:25:49+0000, Jonathan Wakely <jwakely....@gmail.com> wrote:
> 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 :-)
Yeah, I'd noticed that right after (of course) having sent my original
email; fixed in the "v2" that I've now pushed to trunk branch:
commit 618c42d23726be6e2086d452d6718abe5e0daca8
"C++: Adjust implicit '__cxa_bad_cast' prototype to reality", see
attached.
By the way, I've also tested this with 'fn = get_global_binding (name);'
commented out, to force always using the C++ front end-synthesized
prototype (per my understanding).
I've just realized that we might check if some users of 'throw_bad_cast'
have special code to handle the case of 'void *' return type in addition
to 'void', which can now be simplified -- I'll try to look into that next
week.
Grüße
Thomas
>From 618c42d23726be6e2086d452d6718abe5e0daca8 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <tschwi...@baylibre.com>
Date: Wed, 19 Mar 2025 12:18:26 +0100
Subject: [PATCH] C++: Adjust implicit '__cxa_bad_cast' prototype to reality
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 | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/gcc/cp/rtti.cc b/gcc/cp/rtti.cc
index dcf84f17163..158b5ba1397 100644
--- a/gcc/cp/rtti.cc
+++ b/gcc/cp/rtti.cc
@@ -186,7 +186,7 @@ build_headof (tree exp)
/* Get a bad_cast node for the program to throw...
- See libstdc++/exception.cc for __throw_bad_cast */
+ See 'libstdc++-v3/libsupc++/eh_aux_runtime.cc' for '__cxa_bad_cast'. */
static tree
throw_bad_cast (void)
@@ -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);
--
2.34.1
