[gcc r11-4812] libsupc++: Make the destructor parameter to `__cxa_thread_atexit()` use the `__thiscall` calling con

[gcc r11-4812] libsupc++: Make the destructor parameter to `__cxa_thread_atexit()` use the `__thiscall` calling con

[Jonathan Yong]

https://gcc.gnu.org/g:7fc0f78c3f43af1967cb7b1ee8f4947f3b890aa2

commit r11-4812-g7fc0f78c3f43af1967cb7b1ee8f4947f3b890aa2
Author: Liu Hao <lh_mouse@126.com>
Date:   Thu Oct 8 10:26:13 2020 +0800

    libsupc++: Make the destructor parameter to `__cxa_thread_atexit()` use the `__thiscall` calling convention for i686-w64-mingw32
    
    The mingw-w64 implementations of `__cxa_thread_atexit()` and `__cxa_atexit()` have been
    using `__thiscall` since two years ago. Using the default calling convention (which is
    `__cdecl`) causes crashes as explained in PR83562.
    
    Calling conventions have no effect on x86_64-w64-mingw32.
    
    Reference: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83562
    Reference: https://sourceforge.net/p/mingw-w64/mingw-w64/ci/master/tree/mingw-w64-crt/crt/cxa_thread_atexit.c
    Reference: https://sourceforge.net/p/mingw-w64/mingw-w64/ci/f3e0fbb40cbc9f8821db8bd8a0c4dae8ff671e9f/
    Reference: https://github.com/msys2/MINGW-packages/issues/7071
    Signed-off-by: Liu Hao <lh_mouse@126.com>
    
        2020-10-08  Liu Hao  <lh_mouse@126.com>
    
            libstdc++-v3:
            * libsupc++/cxxabi.h: (__cxa_atexit): mark with _GLIBCXX_CDTOR_CALLABI
            (__cxa_thread_atexit): ditto
            * libsupc++/atexit_thread.cc: (__cxa_atexit): mark with
            _GLIBCXX_CDTOR_CALLABI
            (__cxa_thread_atexit): ditto
            (elt): ditto

Diff:
---
 libstdc++-v3/libsupc++/atexit_thread.cc | 14 ++++++++++----
 libstdc++-v3/libsupc++/cxxabi.h         |  8 ++++++++
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/libsupc++/atexit_thread.cc b/libstdc++-v3/libsupc++/atexit_thread.cc
index e97644f8cd4..4f7f982ac6b 100644
--- a/libstdc++-v3/libsupc++/atexit_thread.cc
+++ b/libstdc++-v3/libsupc++/atexit_thread.cc
@@ -30,16 +30,21 @@
 #include <windows.h>
 #endif
 
+// Simplify it a little for this file.
+#ifndef _GLIBCXX_CDTOR_CALLABI
+#  define _GLIBCXX_CDTOR_CALLABI
+#endif
+
 #if _GLIBCXX_HAVE___CXA_THREAD_ATEXIT
 
 // Libc provides __cxa_thread_atexit definition.
 
 #elif _GLIBCXX_HAVE___CXA_THREAD_ATEXIT_IMPL
 
-extern "C" int __cxa_thread_atexit_impl (void (*func) (void *),
+extern "C" int __cxa_thread_atexit_impl (void (_GLIBCXX_CDTOR_CALLABI *func) (void *),
 					 void *arg, void *d);
 extern "C" int
-__cxxabiv1::__cxa_thread_atexit (void (*dtor)(void *),
+__cxxabiv1::__cxa_thread_atexit (void (_GLIBCXX_CDTOR_CALLABI *dtor)(void *),
 				 void *obj, void *dso_handle)
   _GLIBCXX_NOTHROW
 {
@@ -52,7 +57,7 @@ namespace {
   // One element in a singly-linked stack of cleanups.
   struct elt
   {
-    void (*destructor)(void *);
+    void (_GLIBCXX_CDTOR_CALLABI *destructor)(void *);
     void *object;
     elt *next;
 #ifdef _GLIBCXX_THREAD_ATEXIT_WIN32
@@ -116,7 +121,8 @@ namespace {
 }
 
 extern "C" int
-__cxxabiv1::__cxa_thread_atexit (void (*dtor)(void *), void *obj, void */*dso_handle*/)
+__cxxabiv1::__cxa_thread_atexit (void (_GLIBCXX_CDTOR_CALLABI *dtor)(void *),
+				 void *obj, void */*dso_handle*/)
   _GLIBCXX_NOTHROW
 {
   // Do this initialization once.
diff --git a/libstdc++-v3/libsupc++/cxxabi.h b/libstdc++-v3/libsupc++/cxxabi.h
index 000713ecdf8..3d6217a6fac 100644
--- a/libstdc++-v3/libsupc++/cxxabi.h
+++ b/libstdc++-v3/libsupc++/cxxabi.h
@@ -125,14 +125,22 @@ namespace __cxxabiv1
 
   // DSO destruction.
   int
+#ifdef _GLIBCXX_CDTOR_CALLABI
+  __cxa_atexit(void (_GLIBCXX_CDTOR_CALLABI *)(void*), void*, void*) _GLIBCXX_NOTHROW;
+#else
   __cxa_atexit(void (*)(void*), void*, void*) _GLIBCXX_NOTHROW;
+#endif
 
   void
   __cxa_finalize(void*);
 
   // TLS destruction.
   int
+#ifdef _GLIBCXX_CDTOR_CALLABI
+  __cxa_thread_atexit(void (_GLIBCXX_CDTOR_CALLABI *)(void*), void*, void *) _GLIBCXX_NOTHROW;
+#else
   __cxa_thread_atexit(void (*)(void*), void*, void *) _GLIBCXX_NOTHROW;
+#endif
 
   // Pure virtual functions.
   void