fwd: Redefine __MCF_cxa_dtor_union for x86

lhmouse · Jan 22, 2024 · 743c4f4 · 743c4f4
1 parent 12b6010
commit 743c4f4
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Showing 3 changed files with 26 additions and 5 deletions.
diff --git a/mcfgthread/dtor_queue.h b/mcfgthread/dtor_queue.h
@@ -16,7 +16,7 @@ __MCF_C_DECLARATIONS_BEGIN
 /* Define the cxa_atexit queue structure.  */
 struct __MCF_dtor_element
   {
-    __MCF_cxa_dtor_cdecl* __dtor;
+    __MCF_cxa_dtor_union __dtor;
     void* __this;
     void* __dso;
   };

diff --git a/mcfgthread/fwd.h b/mcfgthread/fwd.h
@@ -168,7 +168,28 @@ typedef void _MCF_tls_dtor(void* __ptr);
  * and on the stack, to allow both `__cdecl` and `__thiscall` functions to work
  * properly. The function prototype is declared for compatibility with GCC.  */
 typedef void __MCF_cxa_dtor_cdecl(void* __arg);
-typedef __MCF_cxa_dtor_cdecl __MCF_cxa_dtor_union;
+
+#if defined __i386__ && (defined __GNUC__ || defined __clang__)
+typedef void __thiscall __MCF_cxa_dtor_thiscall(void* __arg);
+typedef union __MCF_cxa_dtor_union __MCF_cxa_dtor_union;
+
+/* Provide dual-ABI support via this union.  */
+union __attribute__((__transparent_union__)) __MCF_cxa_dtor_union
+  {
+    __MCF_cxa_dtor_cdecl* __c_ptr;
+    __MCF_cxa_dtor_thiscall* __tc_ptr;
+
+#  ifdef __cplusplus
+    /* `__transparent_union__` is not supported in C++, so mimic it.  */
+    __MCF_cxa_dtor_union(__MCF_cxa_dtor_cdecl* __p) __MCF_NOEXCEPT : __c_ptr(__p)  { }
+    __MCF_cxa_dtor_union(__MCF_cxa_dtor_stdcall* __p) __MCF_NOEXCEPT : __tc_ptr(__p)  { }
+#  endif
+  };
+#else
+/* FIXME: MSVC doesn't seem to support `__thiscall` on non-member functions.  */
+typedef __MCF_cxa_dtor_cdecl __MCF_cxa_dtor_thiscall;
+typedef __MCF_cxa_dtor_cdecl* __MCF_cxa_dtor_union;
+#endif
 
 /* Define the prototype for `atexit()` and `at_quick_exit()`.  */
 typedef void __MCF_atexit_callback(void);

diff --git a/mcfgthread/xglobals.i b/mcfgthread/xglobals.i
@@ -144,13 +144,13 @@ __MCF_seh_i386_cleanup(__MCF_seh_i386_node* __seh_node) __MCF_NOEXCEPT
  * properly.  */
 __MCF_ALWAYS_INLINE
 void
-__MCF_invoke_cxa_dtor(__MCF_cxa_dtor_cdecl* __dtor, void* __arg)
+__MCF_invoke_cxa_dtor(__MCF_cxa_dtor_union __dtor, void* __arg)
   {
     /* Parameters are `EAX`, `EDX`, `ECX`, `ESP[4]`.  */
-    typedef void __i386_abi_dtor(int, int, void*, void*) __attribute__((__regparm__(3)));
     int __eax, __edx;
     __asm__ ("" : "=a"(__eax), "=d"(__edx));  /* uninitialized.  */
-    (*(__i386_abi_dtor*)(int) __dtor) (__eax, __edx, __arg, __arg);
+    typedef void __i386_abi_dtor(int, int, void*, void*) __attribute__((__regparm__(3)));
+    (*(__i386_abi_dtor*)(int) __dtor.__c_ptr) (__eax, __edx, __arg, __arg);
   }
 #else
 /* Otherwise, SEH is table-based.  */