[Bug target/114968] New: missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[Bug target/114968] New: missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

            Bug ID: 114968
           Summary: missing `__thiscall` attribute on builtin declaration
                    of `__cxa_thread_atexit()`
           Product: gcc
           Version: 14.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lh_mouse at 126 dot com
  Target Milestone: ---

The builtin declaration lacks a `__thiscall` attribute on its first argument
(the callback) and conflicts with the libstdc++ declaration.

This issue has been introduced in eaeaad3fcac4d7a30b5a256410cb59fa1a3fa9dd.

This error is observed when building boost 1.48.

```
gcc.compile.c++
bin.v2\libs\stacktrace\build\gcc-14\release\pch-off\threadapi-win32\threading-multi\visibility-hidden\windbg_cached.o
<built-in>: error: conflicting declaration of C function 'int
__cxxabiv1::__cxa_thread_atexit(void (*)(), void*, void*)'
In file included from ./boost/core/demangle.hpp:32,
                 from ./boost/stacktrace/detail/frame_msvc.ipp:17,
                 from libs/stacktrace/build/../src/windbg_cached.cpp:10:
C:/msys64/mingw32/include/c++/14.0.1/cxxabi.h:140:3: note: previous declaration
'int __cxxabiv1::__cxa_thread_atexit(void (__attribute__((thiscall)) *)(void*),
void*, void*)'
  140 |   __cxa_thread_atexit(void (_GLIBCXX_CDTOR_CALLABI *)(void*), void*,
void *) _GLIBCXX_NOTHROW;
```

[Bug target/114968] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

LIU Hao <lh_mouse at 126 dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |i686-w64-mingw32,
                   |                            |x86_64-w64-mingw32
                 CC|                            |nathan at acm dot org
      Known to work|                            |13.1.0
      Known to fail|                            |14.1.0

--- Comment #1 from LIU Hao <lh_mouse at 126 dot com> ---
CC'ing the author of eaeaad3fcac4d7a30b5a256410cb59fa1a3fa9dd.

The declaration of `__cxa_atexit` probably misses the exact attribute, and
requires a same fix.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|missing `__thiscall`        |[14/15 Regression] missing
                   |attribute on builtin        |`__thiscall` attribute on
                   |declaration of              |builtin declaration of
                   |`__cxa_thread_atexit()`     |`__cxa_thread_atexit()`
           Keywords|                            |rejects-valid
   Target Milestone|---                         |14.2

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |10walls at gmail dot com,
                   |                            |jakub at gcc dot gnu.org,
                   |                            |jason at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Guess you need to add a target hook next to use_aeabi_atexit and
use_atexit_for_cxa_atexit which returns attributes that should be added to a
FUNCTION_TYPE constructed by get_atexit_fn_ptr_type (build_function_type_list
returns a shared type, so if attributes are to be added, it needs to go on a
variant of the type.

On all but mingw ia32 it shouldn't add anything, and guess it shouldn't be done
if
!flag_use_cxa_atexit || !targetm.cxx.use_atexit_for_cxa_atexit ()
A question is what to do about the __tcf_* cleanup functions that might be
sometimes created.

Anyway, seems to be primarily mingw maintainer responsibility given that it is
the only target with such requirements.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Oh, the third argument type for __cxa_throw in cp/except.cc probably needs the
same, so the target hook likely should be called similarly to the libstdc++
macro for that.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #4 from LIU Hao <lh_mouse at 126 dot com> ---
(In reply to Jakub Jelinek from comment #2)
> Guess you need to add a target hook next to use_aeabi_atexit and
> use_atexit_for_cxa_atexit which returns attributes that should be added to a
> FUNCTION_TYPE constructed by get_atexit_fn_ptr_type
> (build_function_type_list returns a shared type, so if attributes are to be
> added, it needs to go on a variant of the type.
> 
> On all but mingw ia32 it shouldn't add anything, and guess it shouldn't be
> done if
> !flag_use_cxa_atexit || !targetm.cxx.use_atexit_for_cxa_atexit ()
> A question is what to do about the __tcf_* cleanup functions that might be
> sometimes created.
> 
> Anyway, seems to be primarily mingw maintainer responsibility given that it
> is the only target with such requirements.

I think a quick and dirty solution should look like this?

```
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 2af026d255d..311f1ca780b 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -9669,6 +9669,13 @@ get_atexit_fn_ptr_type (void)

       fn_type = build_function_type_list (void_type_node,
                                           arg_type, NULL_TREE);
+#ifdef IX86_CALLCVT_THISCALL
+      if (flag_use_cxa_atexit
+          && !targetm.cxx.use_atexit_for_cxa_atexit ())
+        TYPE_ATTRIBUTES (fn_type) = tree_cons (
+                  get_identifier ("thiscall"), NULL_TREE,
+                  TYPE_ATTRIBUTES (fn_type));
+#endif
       atexit_fn_ptr_type_node = build_pointer_type (fn_type);
     }

```

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #5 from LIU Hao <lh_mouse at 126 dot com> ---
(In reply to LIU Hao from comment #4)
> > (build_function_type_list returns a shared type, so if attributes are to be
> > added, it needs to go on a variant of the type.
> > 


Just saw this. So I would have to clone the tree..

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #6 from LIU Hao <lh_mouse at 126 dot com> ---
I suspect this isn't correct. I am getting strange errors like 'ld exited with
code 5'  not sure what could cause it (possibly also recent MSYS2 updates):

```
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 2af026d255d..f5dce6a93bc 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -9669,6 +9669,16 @@ get_atexit_fn_ptr_type (void)

       fn_type = build_function_type_list (void_type_node,
                                          arg_type, NULL_TREE);
+#ifdef IX86_CALLCVT_THISCALL
+      if (flag_use_cxa_atexit
+          && !targetm.cxx.use_atexit_for_cxa_atexit ())
+        {
+          fn_type = copy_node (fn_type);
+          TYPE_ATTRIBUTES (fn_type) = tree_cons (
+                    get_identifier ("thiscall"), NULL_TREE,
+                    TYPE_ATTRIBUTES (fn_type));
+        }
+#endif
       atexit_fn_ptr_type_node = build_pointer_type (fn_type);
     }

diff --git a/gcc/cp/except.cc b/gcc/cp/except.cc
index f1ffda22fd3..00a8843fa2e 100644
--- a/gcc/cp/except.cc
+++ b/gcc/cp/except.cc
@@ -648,6 +648,12 @@ build_throw (location_t loc, tree exp, tsubst_flags_t
complain)
        {
          tree tmp = build_function_type_list (void_type_node,
                                               ptr_type_node, NULL_TREE);
+#ifdef IX86_CALLCVT_THISCALL
+          tmp = copy_node (tmp);
+          TYPE_ATTRIBUTES (tmp) = tree_cons (
+                    get_identifier ("thiscall"), NULL_TREE,
+                    TYPE_ATTRIBUTES (tmp));
+#endif
          cleanup_type = build_pointer_type (tmp);
        }


```

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to LIU Hao from comment #6)
> I suspect this isn't correct. I am getting strange errors like 'ld exited
> with code 5'  not sure what could cause it (possibly also recent MSYS2
> updates):
> 
> ```
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 2af026d255d..f5dce6a93bc 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -9669,6 +9669,16 @@ get_atexit_fn_ptr_type (void)
>        
>        fn_type = build_function_type_list (void_type_node,
>  					  arg_type, NULL_TREE);
> +#ifdef IX86_CALLCVT_THISCALL
> +      if (flag_use_cxa_atexit
> +          && !targetm.cxx.use_atexit_for_cxa_atexit ())
> +        {
> +          fn_type = copy_node (fn_type);
> +          TYPE_ATTRIBUTES (fn_type) = tree_cons (
> +                    get_identifier ("thiscall"), NULL_TREE,
> +                    TYPE_ATTRIBUTES (fn_type));
> +        }
> +#endif
>        atexit_fn_ptr_type_node = build_pointer_type (fn_type);
>      }
>  
> diff --git a/gcc/cp/except.cc b/gcc/cp/except.cc
> index f1ffda22fd3..00a8843fa2e 100644
> --- a/gcc/cp/except.cc
> +++ b/gcc/cp/except.cc
> @@ -648,6 +648,12 @@ build_throw (location_t loc, tree exp, tsubst_flags_t
> complain)
>  	{
>  	  tree tmp = build_function_type_list (void_type_node,
>  					       ptr_type_node, NULL_TREE);
> +#ifdef IX86_CALLCVT_THISCALL
> +          tmp = copy_node (tmp);
> +          TYPE_ATTRIBUTES (tmp) = tree_cons (
> +                    get_identifier ("thiscall"), NULL_TREE,
> +                    TYPE_ATTRIBUTES (tmp));
> +#endif
>  	  cleanup_type = build_pointer_type (tmp);
>  	}
>  
> 
> ```

Besides wrong formatting and the case that you need to build_variant_type (or
build_distinct_type?, one needs to look at what will be normally done if you
do:
void (__attribute__((thiscall)) *fn) (void);
), you really can't do it like that.  IX86_CALLCVT_THISCALL is defined on all
x86_64/i?86 targets, so not limited to mingw 32-bit.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 58123
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58123&action=edit
gcc15-pr114968.patch

This is what I'd do, but completely untested...

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #9 from LIU Hao <lh_mouse at 126 dot com> ---
(In reply to Jakub Jelinek from comment #8)
> Created attachment 58123 [details]
> gcc15-pr114968.patch
> 
> This is what I'd do, but completely untested...

Thanks. I am gonna give it a run.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #10 from LIU Hao <lh_mouse at 126 dot com> ---
(In reply to Jakub Jelinek from comment #8)
> Created attachment 58123 [details]
> gcc15-pr114968.patch
> 
> This is what I'd do, but completely untested...

It does not solve the issue.

Side note: Although I think `-mrtd` should mostly not be useful, the MSVC `/Gz`
and Clang `-mrtd` function do not affect the calling convention of non-static
member functions; they are always `__thiscall`, which means `this` goes in ECX
and the others are passed on stack and popped by callee like `__stdcall`.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #11 from LIU Hao <lh_mouse at 126 dot com> ---
(In reply to LIU Hao from comment #10)
> (In reply to Jakub Jelinek from comment #8)
> > Created attachment 58123 [details]
> > gcc15-pr114968.patch
> > 
> > This is what I'd do, but completely untested...
> 
> It does not solve the issue.
> 

Wait, I can't reproduce the error with
```
namespace std {
class type_info;
}  // namespace std

extern "C" {
int __cxa_at_quick_exit(void (__thiscall* dtor)(void*), void* obj, void* dso)
noexcept;
int __cxa_atexit(void (__thiscall* dtor)(void*), void* obj, void* dso)
noexcept;
int __cxa_thread_atexit(void (__thiscall* dtor)(void*), void* obj, void* dso)
noexcept;
void __cxa_throw(void* obj, std::type_info* type, void (__thiscall*
dtor)(void*));
}  // extern "C"
```

Probably there's something wrong in boost configuration. Investigating.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #12 from LIU Hao <lh_mouse at 126 dot com> ---
testcase:

```
namespace __cxxabiv1
{
extern "C" int __cxa_thread_atexit(void (__thiscall* dtor)(void*), void* obj,
void* dso) noexcept;
}

struct nontrivial
{
  nontrivial();
  ~nontrivial();
};

void*
get_data()
{
  thread_local nontrivial nt;
  return &nt;
}
```

```
E:\lh_mouse\Desktop>g++ test.cc
<built-in>: error: conflicting declaration of C function 'int
__cxxabiv1::__cxa_thread_atexit(void (*)(), void*, void*)'
test.cc:3:18: note: previous declaration 'int
__cxxabiv1::__cxa_thread_atexit(void (__attribute__((thiscall)) *)(void*),
void*, void*)'
    3 |   extern "C" int __cxa_thread_atexit(void (__thiscall* dtor)(void*),
void* obj, void* dso) noexcept;
      |                  ^~~~~~~~~~~~~~~~~~~
```

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #13 from LIU Hao <lh_mouse at 126 dot com> ---
I am using a modified patch:

```
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 4d6b2b98761..fbd9b4dac2e 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -25799,6 +25799,24 @@ ix86_bitint_type_info (int n, struct bitint_info
*info)
   return true;
 }

+/* Returns modified FUNCTION_TYPE for cdtor callabi.  */
+tree
+ix86_cxx_adjust_cdtor_callabi_fntype (tree fntype)
+{
+fprintf(stderr, "TARGET_64BIT = %d\n", (bool) TARGET_64BIT);
+fprintf(stderr, "TARGET_RTD = %d\n", (bool) TARGET_RTD);
+fprintf(stderr, "ix86_function_type_abi = %d\n", ix86_function_type_abi
(fntype));
+  if (TARGET_64BIT
+      || TARGET_RTD
+      || ix86_function_type_abi (fntype) != MS_ABI)
+    return fntype;
+  /* For 32-bit MS ABI add thiscall attribute.  */
+  tree attribs = tree_cons (get_identifier ("thiscall"), NULL_TREE,
+         TYPE_ATTRIBUTES (fntype));
+fprintf(stderr, "__thiscall applied!\n");
+  return build_type_attribute_variant (fntype, attribs);
+}
+
 /* Implement PUSH_ROUNDING.  On 386, we have pushw instruction that
    decrements by exactly 2 no matter what the position was, there is no pushb.

```

There is no message when compiling the testcase:

```
E:\lh_mouse\Desktop>g++ test.cc -Wall -Wextra
<built-in>: error: conflicting declaration of C function 'int
__cxxabiv1::__cxa_thread_atexit(void (*)(), void*, void*)'
test.cc:3:16: note: previous declaration 'int
__cxxabiv1::__cxa_thread_atexit(void (__attribute__((thiscall)) *)(void*),
void*, void*)'
    3 | extern "C" int __cxa_thread_atexit(void (__thiscall* dtor)(void*),
void* obj, void* dso) noexcept;
      |                ^~~~~~~~~~~~~~~~~~~
```

So I suspect this is a wrong place to look at.. ?

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #14 from LIU Hao <lh_mouse at 126 dot com> ---
I suspect it's because that `get_atexit_fn_ptr_type` is shared by `atexit` and
`__cxa_thread_atexit` but the destructors for them do not use the same calling
convention ..

So I should make a copy of it, as well as `atexit_fn_ptr_type_node`.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #15 from LIU Hao <lh_mouse at 126 dot com> ---
Created attachment 58124
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58124&action=edit
proposed patch v2

Update the patch. Did a quick test on i686-w64-mingw32 and seemed to solve the
issue.

Rebuilding everything now.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #16 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
What is the reason behind
/* mingw32 atexit function is safe to use in shared libraries.  Use it
   to register C++ static destructors.  */
#define TARGET_CXX_USE_ATEXIT_FOR_CXA_ATEXIT hook_bool_void_true
?
Couldn't we just drop that?
I mean, when using atexit, GCC needs to emit wrapper functions around the
destructors,
like
__tcf_0:
        pushq   %rbp
        .seh_pushreg    %rbp
        movq    %rsp, %rbp
        .seh_setframe   %rbp, 0
        subq    $32, %rsp
        .seh_stackalloc 32
        .seh_endprologue
        leaq    _ZZ3foovE1s(%rip), %rax
        movq    %rax, %rcx
        call    _ZN1SD1Ev
        nop
        addq    $32, %rsp
        popq    %rbp
        ret
while with __cxa_atexit one can just pass the destructor itself to the
__cxa_atexit function (indeed with slightly more instructions there because in
addition to the function pointer it needs to pass the address of the object and
__dso_handle).
But it is still smaller.

Anyway, if there is some strong reason to keep it, I think it would be better
to avoid adding yet another GTY tree, the __cxa_throw last argument type is the
same as __cxa_atexit/__cxa_thread_atexit.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #58123|0                           |1
        is obsolete|                            |

--- Comment #17 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 58125
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58125&action=edit
gcc15-pr114968.patch

Here is an updated patch.
Note, even when not taking thiscall attribute into consideration, the existing
code was wrong on the !targetm.cxx.use_atexit_for_cxa_atexit () targets (aka
mingw), because it would happily use the atexit function argument type (aka
void (*) ()) for __cxa_thread_atexit.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #18 from LIU Hao <lh_mouse at 126 dot com> ---
(In reply to Jakub Jelinek from comment #16)
> What is the reason behind
> /* mingw32 atexit function is safe to use in shared libraries.  Use it
>    to register C++ static destructors.  */
> #define TARGET_CXX_USE_ATEXIT_FOR_CXA_ATEXIT hook_bool_void_true
> ?
> Couldn't we just drop that?

I think so. We have a statically linked `atexit()` much like glibc [1]. However
we have added `__cxa_atexit()` a couple of years ago, so it might be preferred.
As the Windows system library does not provide `__cxa_*` routines, those
functions are also linked statically, so they ignore the DSO handle parameter.


 [1]
https://github.com/mingw-w64/mingw-w64/blob/19cf5d171f6df208b27271b40014c66d2b44e38b/mingw-w64-crt/crt/crtdll.c#L205
 [2]
https://github.com/mingw-w64/mingw-w64/blob/19cf5d171f6df208b27271b40014c66d2b44e38b/mingw-w64-crt/crt/cxa_atexit.c#L11


> while with __cxa_atexit one can just pass the destructor itself to the
> __cxa_atexit function (indeed with slightly more instructions there because
> in addition to the function pointer it needs to pass the address of the
> object and __dso_handle).
> But it is still smaller.

Can `./configure --enable-__cxa_atexit` be safely used? Documentation says it's
only available with glibc [3], but I don't see any stuff specific to glibc.

 [3] https://gcc.gnu.org/install/configure.html


> Anyway, if there is some strong reason to keep it, I think it would be
> better to avoid adding yet another GTY tree, the __cxa_throw last argument
> type is the same as __cxa_atexit/__cxa_thread_atexit.

Maybe it can be kept for backward compatibility.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #19 from LIU Hao <lh_mouse at 126 dot com> ---
(In reply to Jakub Jelinek from comment #17)
> Created attachment 58125 [details]
> gcc15-pr114968.patch
> 
> Here is an updated patch.
> Note, even when not taking thiscall attribute into consideration, the
> existing
> code was wrong on the !targetm.cxx.use_atexit_for_cxa_atexit () targets (aka
> mingw), because it would happily use the atexit function argument type (aka
> void (*) ()) for __cxa_thread_atexit.

Bootstrapped successfully on {i686,x86_64}-w64-mingw32. Also rebuilt mingw-w64
CRT, binutils, GDB and boost. Everything went well.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #20 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Thanks, I'll test it myself on x86_64-linux/i686-linux and post if it succeeds.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #21 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:e5d8fd9ce05611093191d500ebc39f150d0ece2b

commit r15-358-ge5d8fd9ce05611093191d500ebc39f150d0ece2b
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri May 10 09:21:38 2024 +0200

    c++, mingw: Fix up types of dtor hooks to
__cxa_{,thread_}atexit/__cxa_throw on mingw ia32 [PR114968]

    __cxa_atexit/__cxa_thread_atexit/__cxa_throw functions accept function
    pointers to usually directly destructors rather than wrappers around
    them.
    Now, mingw ia32 uses implicitly __attribute__((thiscall)) calling
    conventions for METHOD_TYPE (where the this pointer is passed in %ecx
    register, the rest on the stack), so these functions use:
    in config/os/mingw32/os_defines.h:
     #if defined (__i386__)
     #define _GLIBCXX_CDTOR_CALLABI __thiscall
     #endif
    in libsupc++/cxxabi.h
    __cxa_atexit(void (_GLIBCXX_CDTOR_CALLABI *)(void*), void*, void*)
_GLIBCXX_NOTHROW;
    __cxa_thread_atexit(void (_GLIBCXX_CDTOR_CALLABI *)(void*), void*, void *)
_GLIBCXX_NOTHROW;
    __cxa_throw(void*, std::type_info*, void (_GLIBCXX_CDTOR_CALLABI *) (void
*))
    __attribute__((__noreturn__));

    Now, mingw for some weird reason uses
     #define TARGET_CXX_USE_ATEXIT_FOR_CXA_ATEXIT hook_bool_void_true
    so it never actually uses __cxa_atexit, but does use __cxa_thread_atexit
    and __cxa_throw.  Recent changes for modules result in more detailed
    __cxa_*atexit/__cxa_throw prototypes precreated by the compiler, and if
    that happens and one also includes <cxxabi.h>, the compiler complains about
    mismatches in the prototypes.

    One thing is the missing thiscall attribute on the FUNCTION_TYPE, the
    other problem is that all of atexit/__cxa_atexit/__cxa_thread_atexit
    get function pointer types created by a single function,
    get_atexit_fn_ptr_type (), which creates it depending on if atexit
    or __cxa_atexit will be used as either void(*)(void) or void(*)(void *),
    but when using atexit and __cxa_thread_atexit it uses the wrong function
    type for __cxa_thread_atexit.

    The following patch adds a target hook to add the thiscall attribute to the
    function pointers, and splits the get_atexit_fn_ptr_type () function into
    get_atexit_fn_ptr_type () and get_cxa_atexit_fn_ptr_type (), the former
always
    creates shared void(*)(void) type, the latter creates either
    void(*)(void*) (on most targets) or void(__attribute__((thiscall))*)(void*)
    (on mingw ia32).  So that we don't waiste another GTY global tree for it,
    because cleanup_type used for the same purpose for __cxa_throw should be
    the same, the code changes it to use that type too.

    In register_dtor_fn then based on the decision whether to use atexit,
    __cxa_atexit or __cxa_thread_atexit it picks the right function pointer
    type, and also if it decides to emit a __tcf_* wrapper for the cleanup,
    uses that type for that wrapper so that it agrees on calling convention.

    2024-05-10  Jakub Jelinek  <jakub@redhat.com>

            PR target/114968
    gcc/
            * target.def (use_atexit_for_cxa_atexit): Remove spurious space
            from comment.
            (adjust_cdtor_callabi_fntype): New cxx target hook.
            * targhooks.h (default_cxx_adjust_cdtor_callabi_fntype): Declare.
            * targhooks.cc (default_cxx_adjust_cdtor_callabi_fntype): New
            function.
            * doc/tm.texi.in (TARGET_CXX_ADJUST_CDTOR_CALLABI_FNTYPE): Add.
            * doc/tm.texi: Regenerate.
            * config/i386/i386.cc (ix86_cxx_adjust_cdtor_callabi_fntype): New
            function.
            (TARGET_CXX_ADJUST_CDTOR_CALLABI_FNTYPE): Redefine.
    gcc/cp/
            * cp-tree.h (atexit_fn_ptr_type_node, cleanup_type): Adjust macro
            comments.
            (get_cxa_atexit_fn_ptr_type): Declare.
            * decl.cc (get_atexit_fn_ptr_type): Adjust function comment, only
            build type for atexit argument.
            (get_cxa_atexit_fn_ptr_type): New function.
            (get_atexit_node): Call get_cxa_atexit_fn_ptr_type rather than
            get_atexit_fn_ptr_type when using __cxa_atexit.
            (get_thread_atexit_node): Call get_cxa_atexit_fn_ptr_type
            rather than get_atexit_fn_ptr_type.
            (start_cleanup_fn): Add ob_parm argument, call
            get_cxa_atexit_fn_ptr_type or get_atexit_fn_ptr_type depending
            on it and create PARM_DECL also based on that argument.
            (register_dtor_fn): Adjust start_cleanup_fn caller, use
            get_cxa_atexit_fn_ptr_type rather than get_atexit_fn_ptr_type
            for use_dtor casts.
            * except.cc (build_throw): Use get_cxa_atexit_fn_ptr_type ().

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #22 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Does even the committed version work fine on mingw32?

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #23 from LIU Hao <lh_mouse at 126 dot com> ---
I am afraid I can't do a complete bootstrap any more due to
https://sourceware.org/bugzilla/show_bug.cgi?id=31720. LD is segfaulting
randomly.

I will backport the commit to GCC 14 branch and make a non-bootstrapped build,
then build others as usual.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #24 from LIU Hao <lh_mouse at 126 dot com> ---
GCC 14 branch built successfully on i686-w64-mingw32 with the backported
commit. I have also built boost 1.84 successfully.

I'm now trying to fix the LD fault..

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #25 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-14 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:a805de33f7be4f6886906ca5f4da493f3b743c76

commit r14-10193-ga805de33f7be4f6886906ca5f4da493f3b743c76
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri May 10 09:21:38 2024 +0200

    c++, mingw: Fix up types of dtor hooks to
__cxa_{,thread_}atexit/__cxa_throw on mingw ia32 [PR114968]

    __cxa_atexit/__cxa_thread_atexit/__cxa_throw functions accept function
    pointers to usually directly destructors rather than wrappers around
    them.
    Now, mingw ia32 uses implicitly __attribute__((thiscall)) calling
    conventions for METHOD_TYPE (where the this pointer is passed in %ecx
    register, the rest on the stack), so these functions use:
    in config/os/mingw32/os_defines.h:
     #if defined (__i386__)
     #define _GLIBCXX_CDTOR_CALLABI __thiscall
     #endif
    in libsupc++/cxxabi.h
    __cxa_atexit(void (_GLIBCXX_CDTOR_CALLABI *)(void*), void*, void*)
_GLIBCXX_NOTHROW;
    __cxa_thread_atexit(void (_GLIBCXX_CDTOR_CALLABI *)(void*), void*, void *)
_GLIBCXX_NOTHROW;
    __cxa_throw(void*, std::type_info*, void (_GLIBCXX_CDTOR_CALLABI *) (void
*))
    __attribute__((__noreturn__));

    Now, mingw for some weird reason uses
     #define TARGET_CXX_USE_ATEXIT_FOR_CXA_ATEXIT hook_bool_void_true
    so it never actually uses __cxa_atexit, but does use __cxa_thread_atexit
    and __cxa_throw.  Recent changes for modules result in more detailed
    __cxa_*atexit/__cxa_throw prototypes precreated by the compiler, and if
    that happens and one also includes <cxxabi.h>, the compiler complains about
    mismatches in the prototypes.

    One thing is the missing thiscall attribute on the FUNCTION_TYPE, the
    other problem is that all of atexit/__cxa_atexit/__cxa_thread_atexit
    get function pointer types created by a single function,
    get_atexit_fn_ptr_type (), which creates it depending on if atexit
    or __cxa_atexit will be used as either void(*)(void) or void(*)(void *),
    but when using atexit and __cxa_thread_atexit it uses the wrong function
    type for __cxa_thread_atexit.

    The following patch adds a target hook to add the thiscall attribute to the
    function pointers, and splits the get_atexit_fn_ptr_type () function into
    get_atexit_fn_ptr_type () and get_cxa_atexit_fn_ptr_type (), the former
always
    creates shared void(*)(void) type, the latter creates either
    void(*)(void*) (on most targets) or void(__attribute__((thiscall))*)(void*)
    (on mingw ia32).  So that we don't waiste another GTY global tree for it,
    because cleanup_type used for the same purpose for __cxa_throw should be
    the same, the code changes it to use that type too.

    In register_dtor_fn then based on the decision whether to use atexit,
    __cxa_atexit or __cxa_thread_atexit it picks the right function pointer
    type, and also if it decides to emit a __tcf_* wrapper for the cleanup,
    uses that type for that wrapper so that it agrees on calling convention.

    2024-05-10  Jakub Jelinek  <jakub@redhat.com>

            PR target/114968
    gcc/
            * target.def (use_atexit_for_cxa_atexit): Remove spurious space
            from comment.
            (adjust_cdtor_callabi_fntype): New cxx target hook.
            * targhooks.h (default_cxx_adjust_cdtor_callabi_fntype): Declare.
            * targhooks.cc (default_cxx_adjust_cdtor_callabi_fntype): New
            function.
            * doc/tm.texi.in (TARGET_CXX_ADJUST_CDTOR_CALLABI_FNTYPE): Add.
            * doc/tm.texi: Regenerate.
            * config/i386/i386.cc (ix86_cxx_adjust_cdtor_callabi_fntype): New
            function.
            (TARGET_CXX_ADJUST_CDTOR_CALLABI_FNTYPE): Redefine.
    gcc/cp/
            * cp-tree.h (atexit_fn_ptr_type_node, cleanup_type): Adjust macro
            comments.
            (get_cxa_atexit_fn_ptr_type): Declare.
            * decl.cc (get_atexit_fn_ptr_type): Adjust function comment, only
            build type for atexit argument.
            (get_cxa_atexit_fn_ptr_type): New function.
            (get_atexit_node): Call get_cxa_atexit_fn_ptr_type rather than
            get_atexit_fn_ptr_type when using __cxa_atexit.
            (get_thread_atexit_node): Call get_cxa_atexit_fn_ptr_type
            rather than get_atexit_fn_ptr_type.
            (start_cleanup_fn): Add ob_parm argument, call
            get_cxa_atexit_fn_ptr_type or get_atexit_fn_ptr_type depending
            on it and create PARM_DECL also based on that argument.
            (register_dtor_fn): Adjust start_cleanup_fn caller, use
            get_cxa_atexit_fn_ptr_type rather than get_atexit_fn_ptr_type
            for use_dtor casts.
            * except.cc (build_throw): Use get_cxa_atexit_fn_ptr_type ().

    (cherry picked from commit e5d8fd9ce05611093191d500ebc39f150d0ece2b)

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #26 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed then.

[Bug target/114968] [14/15 Regression] missing `__thiscall` attribute on builtin declaration of `__cxa_thread_atexit()`

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114968

--- Comment #27 from LIU Hao <lh_mouse at 126 dot com> ---
Thank you!