Support -Wabi warning about backward compatibility.

gcc/c-family/
	* c.opt (Wabi=, fabi-compat-version): New.
	* c-opts.c (c_common_handle_option): Handle -Wabi=.
	(c_common_post_options): Handle flag_abi_compat_version default.
	Disallow -fabi-compat-version=1.
	* c-common.h (abi_version_crosses): New.
gcc/cp/
	* call.c (convert_arg_to_ellipsis): Use abi_version_crosses.
	* cvt.c (type_promotes_to): Likewise.
	* mangle.c (write_type, write_expression): Likewise.
	(write_name, write_template_arg): Likewise.
	(mangle_decl): Make alias based on flag_abi_compat_version.
	Emit -Wabi warning here.
	(finish_mangling_internal): Not here.  Drop warn parm.
	(finish_mangling_get_identifier, finish_mangling): Adjust.
	(mangle_type_string, mangle_special_for_type): Adjust.
	(mangle_ctor_vtbl_for_type, mangle_thunk): Adjust.
	(mangle_guard_variable, mangle_tls_init_fn): Adjust.
	(mangle_tls_wrapper_fn, mangle_ref_init_variable): Adjust.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@211594 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 20 insertions, 14 deletions

diff --git a/gcc/cp/cvt.c b/gcc/cp/cvt.c
index 2a827237f28..1dec9cc7f0e 100644
--- a/gcc/cp/cvt.c
+++ b/gcc/cp/cvt.c
@@ -1701,13 +1701,9 @@ type_promotes_to (tree type)
   if (TREE_CODE (type) == BOOLEAN_TYPE)
     type = integer_type_node;
 
-  /* Scoped enums don't promote, but pretend they do for backward ABI bug
-     compatibility wrt varargs.  */
-  else if (SCOPED_ENUM_P (type) && abi_version_at_least (6))
-    ;
-
   /* Normally convert enums to int, but convert wide enums to something
-     wider.  */
+     wider.  Scoped enums don't promote, but pretend they do for backward
+     ABI bug compatibility wrt varargs.  */
   else if (TREE_CODE (type) == ENUMERAL_TYPE
 	   || type == char16_type_node
 	   || type == char32_type_node
@@ -1716,16 +1712,26 @@ type_promotes_to (tree type)
       int precision = MAX (TYPE_PRECISION (type),
 			   TYPE_PRECISION (integer_type_node));
       tree totype = c_common_type_for_size (precision, 0);
+      tree prom = type;
+      if (TREE_CODE (prom) == ENUMERAL_TYPE)
+	prom = ENUM_UNDERLYING_TYPE (prom);
+      if (TYPE_UNSIGNED (prom)
+	  && ! int_fits_type_p (TYPE_MAX_VALUE (prom), totype))
+	prom = c_common_type_for_size (precision, 1);
+      else
+	prom = totype;
       if (SCOPED_ENUM_P (type))
-	warning (OPT_Wabi, "scoped enum %qT will not promote to an integral "
-		 "type in a future version of GCC", type);
-      if (TREE_CODE (type) == ENUMERAL_TYPE)
-	type = ENUM_UNDERLYING_TYPE (type);
-      if (TYPE_UNSIGNED (type)
-	  && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
-	type = c_common_type_for_size (precision, 1);
+	{
+	  if (abi_version_crosses (6)
+	      && TYPE_MODE (prom) != TYPE_MODE (type))
+	    warning (OPT_Wabi, "scoped enum %qT passed through ... as "
+		     "%qT before -fabi-version=6, %qT after",
+		     type, prom, ENUM_UNDERLYING_TYPE (type));
+	  if (!abi_version_at_least (6))
+	    type = prom;
+	}
       else
-	type = totype;
+	type = prom;
     }
   else if (c_promoting_integer_type_p (type))
     {