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)

gcc/config/i386/i386.cc

@@ -25799,6 +25799,20 @@ 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)
+{
+  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));
+  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.
 
@@ -26410,6 +26424,8 @@ static const scoped_attribute_specs *const ix86_attribute_table[] =
 #define TARGET_C_EXCESS_PRECISION ix86_get_excess_precision
 #undef TARGET_C_BITINT_TYPE_INFO
 #define TARGET_C_BITINT_TYPE_INFO ix86_bitint_type_info
+#undef TARGET_CXX_ADJUST_CDTOR_CALLABI_FNTYPE
+#define TARGET_CXX_ADJUST_CDTOR_CALLABI_FNTYPE ix86_cxx_adjust_cdtor_callabi_fntype
 #undef TARGET_PROMOTE_PROTOTYPES
 #define TARGET_PROMOTE_PROTOTYPES hook_bool_const_tree_true
 #undef TARGET_PUSH_ARGUMENT

gcc/cp/cp-tree.h

@@ -369,8 +369,7 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
 #define throw_fn			cp_global_trees[CPTI_THROW_FN]
 #define rethrow_fn			cp_global_trees[CPTI_RETHROW_FN]
 
-/* The type of the function-pointer argument to "__cxa_atexit" (or
-   "std::atexit", if "__cxa_atexit" is not being used).  */
+/* The type of the function-pointer argument to "std::atexit".  */
 #define atexit_fn_ptr_type_node         cp_global_trees[CPTI_ATEXIT_FN_PTR_TYPE]
 
 /* A pointer to `std::atexit'.  */
@@ -385,7 +384,8 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
 /* The declaration of the dynamic_cast runtime.  */
 #define dynamic_cast_node		cp_global_trees[CPTI_DCAST]
 
-/* The type of a destructor.  */
+/* The type of a destructor, passed to __cxa_atexit, __cxa_thread_atexit
+   or __cxa_throw.  */
 #define cleanup_type			cp_global_trees[CPTI_CLEANUP_TYPE]
 
 /* The type of the vtt parameter passed to subobject constructors and
@@ -7065,6 +7065,7 @@ extern tree check_default_argument		(tree, tree, tsubst_flags_t);
 extern int wrapup_namespace_globals		();
 extern tree create_implicit_typedef		(tree, tree);
 extern int local_variable_p			(const_tree);
+extern tree get_cxa_atexit_fn_ptr_type		();
 extern tree register_dtor_fn			(tree);
 extern tmpl_spec_kind current_tmpl_spec_kind	(int);
 extern tree cxx_builtin_function		(tree decl);

gcc/cp/decl.cc

@@ -93,7 +93,7 @@ static void record_key_method_defined (tree);
 static tree create_array_type_for_decl (tree, tree, tree, location_t);
 static tree get_atexit_node (void);
 static tree get_dso_handle_node (void);
-static tree start_cleanup_fn (void);
+static tree start_cleanup_fn (bool);
 static void end_cleanup_fn (void);
 static tree cp_make_fname_decl (location_t, tree, int);
 static void initialize_predefined_identifiers (void);
@@ -9647,34 +9647,39 @@ declare_global_var (tree name, tree type)
   return decl;
 }
 
-/* Returns the type for the argument to "__cxa_atexit" (or "atexit",
-   if "__cxa_atexit" is not being used) corresponding to the function
+/* Returns the type for the argument to "atexit" corresponding to the function
    to be called when the program exits.  */
 
 static tree
-get_atexit_fn_ptr_type (void)
+get_atexit_fn_ptr_type ()
 {
-  tree fn_type;
-
   if (!atexit_fn_ptr_type_node)
     {
-      tree arg_type;
-      if (flag_use_cxa_atexit 
-	  && !targetm.cxx.use_atexit_for_cxa_atexit ())
-	/* The parameter to "__cxa_atexit" is "void (*)(void *)".  */
-	arg_type = ptr_type_node;
-      else
-	/* The parameter to "atexit" is "void (*)(void)".  */
-	arg_type = NULL_TREE;
-      
-      fn_type = build_function_type_list (void_type_node,
-					  arg_type, NULL_TREE);
+      tree fn_type = build_function_type_list (void_type_node, NULL_TREE);
       atexit_fn_ptr_type_node = build_pointer_type (fn_type);
     }
 
   return atexit_fn_ptr_type_node;
 }
 
+/* Returns the type for the argument to "__cxa_atexit", "__cxa_thread_atexit"
+   or "__cxa_throw" corresponding to the destructor to be called when the
+   program exits.  */
+
+tree
+get_cxa_atexit_fn_ptr_type ()
+{
+  if (!cleanup_type)
+    {
+      tree fntype = build_function_type_list (void_type_node,
+					      ptr_type_node, NULL_TREE);
+      fntype = targetm.cxx.adjust_cdtor_callabi_fntype (fntype);
+      cleanup_type = build_pointer_type (fntype);
+    }
+
+  return cleanup_type;
+}
+
 /* Returns a pointer to the `atexit' function.  Note that if
    FLAG_USE_CXA_ATEXIT is nonzero, then this will actually be the new
    `__cxa_atexit' function specified in the IA64 C++ ABI.  */
@@ -9705,7 +9710,7 @@ get_atexit_node (void)
       use_aeabi_atexit = targetm.cxx.use_aeabi_atexit ();
       /* First, build the pointer-to-function type for the first
 	 argument.  */
-      fn_ptr_type = get_atexit_fn_ptr_type ();
+      fn_ptr_type = get_cxa_atexit_fn_ptr_type ();
       /* Then, build the rest of the argument types.  */
       argtype2 = ptr_type_node;
       if (use_aeabi_atexit)
@@ -9788,7 +9793,7 @@ get_thread_atexit_node (void)
 
      int __cxa_thread_atexit (void (*)(void *), void *, void *) */
   tree fn_type = build_function_type_list (integer_type_node,
-					   get_atexit_fn_ptr_type (),
+					   get_cxa_atexit_fn_ptr_type (),
 					   ptr_type_node, ptr_type_node,
 					   NULL_TREE);
 
@@ -9830,12 +9835,13 @@ get_dso_handle_node (void)
 }
 
 /* Begin a new function with internal linkage whose job will be simply
-   to destroy some particular variable.  */
+   to destroy some particular variable.  OB_PARM is true if object pointer
+   is passed to the cleanup function, otherwise no argument is passed.  */
 
 static GTY(()) int start_cleanup_cnt;
 
 static tree
-start_cleanup_fn (void)
+start_cleanup_fn (bool ob_parm)
 {
   char name[32];
 
@@ -9846,8 +9852,9 @@ start_cleanup_fn (void)
 
   /* Build the name of the function.  */
   sprintf (name, "__tcf_%d", start_cleanup_cnt++);
+  tree fntype = TREE_TYPE (ob_parm ? get_cxa_atexit_fn_ptr_type ()
+				   : get_atexit_fn_ptr_type ());
   /* Build the function declaration.  */
-  tree fntype = TREE_TYPE (get_atexit_fn_ptr_type ());
   tree fndecl = build_lang_decl (FUNCTION_DECL, get_identifier (name), fntype);
   DECL_CONTEXT (fndecl) = FROB_CONTEXT (current_namespace);
   /* It's a function with internal linkage, generated by the
@@ -9860,7 +9867,7 @@ start_cleanup_fn (void)
      emissions this way.  */
   DECL_DECLARED_INLINE_P (fndecl) = 1;
   DECL_INTERFACE_KNOWN (fndecl) = 1;
-  if (flag_use_cxa_atexit && !targetm.cxx.use_atexit_for_cxa_atexit ())
+  if (ob_parm)
     {
       /* Build the parameter.  */
       tree parmdecl = cp_build_parm_decl (fndecl, NULL_TREE, ptr_type_node);
@@ -9937,8 +9944,8 @@ register_dtor_fn (tree decl)
       build_cleanup (decl);
   
       /* Now start the function.  */
-      cleanup = start_cleanup_fn ();
-      
+      cleanup = start_cleanup_fn (ob_parm);
+
       /* Now, recompute the cleanup.  It may contain SAVE_EXPRs that refer
 	 to the original function, rather than the anonymous one.  That
 	 will make the back end think that nested functions are in use,
@@ -9967,7 +9974,7 @@ register_dtor_fn (tree decl)
     {
       /* We must convert CLEANUP to the type that "__cxa_atexit"
 	 expects.  */
-      cleanup = build_nop (get_atexit_fn_ptr_type (), cleanup);
+      cleanup = build_nop (get_cxa_atexit_fn_ptr_type (), cleanup);
       /* "__cxa_atexit" will pass the address of DECL to the
 	 cleanup function.  */
       mark_used (decl);

gcc/cp/except.cc

@@ -645,11 +645,7 @@ build_throw (location_t loc, tree exp, tsubst_flags_t complain)
 
       /* The CLEANUP_TYPE is the internal type of a destructor.  */
       if (!cleanup_type)
-	{
-	  tree tmp = build_function_type_list (void_type_node,
-					       ptr_type_node, NULL_TREE);
-	  cleanup_type = build_pointer_type (tmp);
-	}
+	cleanup_type = get_cxa_atexit_fn_ptr_type ();
 
       if (!throw_fn)
 	{

gcc/doc/tm.texi

@@ -11117,6 +11117,14 @@ shared libraries are run in the correct order when the libraries are
 unloaded. The default is to return false.
 @end deftypefn
 
+@deftypefn {Target Hook} tree TARGET_CXX_ADJUST_CDTOR_CALLABI_FNTYPE (tree @var{fntype})
+This hook returns a possibly modified @code{FUNCTION_TYPE} for arguments
+to @code{__cxa_atexit}, @code{__cxa_thread_atexit} or @code{__cxa_throw}
+function pointers.  ABIs like mingw32 require special attributes to be added
+to function types pointed to by arguments of these functions.
+The default is to return the passed argument unmodified.
+@end deftypefn
+
 @deftypefn {Target Hook} void TARGET_CXX_ADJUST_CLASS_AT_DEFINITION (tree @var{type})
 @var{type} is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that has just
 been defined.  Use this hook to make adjustments to the class (eg, tweak

gcc/doc/tm.texi.in

@@ -7223,6 +7223,8 @@ floating-point support; they are not included in this mechanism.
 
 @hook TARGET_CXX_USE_ATEXIT_FOR_CXA_ATEXIT
 
+@hook TARGET_CXX_ADJUST_CDTOR_CALLABI_FNTYPE
+
 @hook TARGET_CXX_ADJUST_CLASS_AT_DEFINITION
 
 @hook TARGET_CXX_DECL_MANGLING_CONTEXT

gcc/target.def

@@ -6498,7 +6498,7 @@ is in effect.  The default is to return false to use @code{__cxa_atexit}.",
  hook_bool_void_false)
 
 /* Returns true if target may use atexit in the same manner as
-   __cxa_atexit  to register static destructors.  */
+   __cxa_atexit to register static destructors.  */
 DEFHOOK
 (use_atexit_for_cxa_atexit,
  "This hook returns true if the target @code{atexit} function can be used\n\
@@ -6509,6 +6509,17 @@ unloaded. The default is to return false.",
  bool, (void),
  hook_bool_void_false)
 
+/* Returns modified FUNCTION_TYPE for cdtor callabi.  */
+DEFHOOK
+(adjust_cdtor_callabi_fntype,
+ "This hook returns a possibly modified @code{FUNCTION_TYPE} for arguments\n\
+to @code{__cxa_atexit}, @code{__cxa_thread_atexit} or @code{__cxa_throw}\n\
+function pointers.  ABIs like mingw32 require special attributes to be added\n\
+to function types pointed to by arguments of these functions.\n\
+The default is to return the passed argument unmodified.",
+ tree, (tree fntype),
+ default_cxx_adjust_cdtor_callabi_fntype)
+
 DEFHOOK
 (adjust_class_at_definition,
 "@var{type} is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that has just\n\

gcc/targhooks.cc

@@ -329,6 +329,14 @@ default_cxx_get_cookie_size (tree type)
   return cookie_size;
 }
 
+/* Returns modified FUNCTION_TYPE for cdtor callabi.  */
+
+tree
+default_cxx_adjust_cdtor_callabi_fntype (tree fntype)
+{
+  return fntype;
+}
+
 /* Return true if a parameter must be passed by reference.  This version
    of the TARGET_PASS_BY_REFERENCE hook uses just MUST_PASS_IN_STACK.  */
 

gcc/targhooks.h

@@ -65,6 +65,7 @@ extern machine_mode default_mode_for_suffix (char);
 
 extern tree default_cxx_guard_type (void);
 extern tree default_cxx_get_cookie_size (tree);
+extern tree default_cxx_adjust_cdtor_callabi_fntype (tree);
 
 extern bool hook_pass_by_reference_must_pass_in_stack
   (cumulative_args_t, const function_arg_info &);