We don't yet have clear agreement on removing -Wtraditional (although
it seems there is little to no use for most of the warnings therein),
so fix the bug in its interaction with -std=gnu23 to continue progress
on making -std=gnu23 the default while -Wtraditional remains under
discussion.
The warning for ISO C function definitions with -Wtraditional properly
covers (void), but also wrongly warned for () in C23 mode as that has
the same semantics as (void) in that case. Keep track in c_arg_info
of when () was converted to (void) for C23 so that -Wtraditional can
avoid warning in that case (with an appropriate comment on the
definition of the new field to make clear it can be removed along with
-Wtraditional).
Bootstrapped with no regressions for x86_64-pc-linux-gnu.
gcc/c/
* c-tree.h (c_arg_info): Add c23_empty_parens.
* c-decl.cc (grokparms): Set c23_empty_parens.
(build_arg_info): Clear c23_empty_parens.
(store_parm_decls_newstyle): Do not give -Wtraditional warning for
ISO C function definition if c23_empty_parens.
gcc/testsuite/
* gcc.dg/wtr-gnu17-1.c, gcc.dg/wtr-gnu23-1.c: New tests.
diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 491c24b9fe7..3733ecfc13f 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -8519,7 +8519,10 @@ grokparms (struct c_arg_info *arg_info, bool
funcdef_flag)
&& !arg_types
&& !arg_info->parms
&& !arg_info->no_named_args_stdarg_p)
- arg_types = arg_info->types = void_list_node;
+ {
+ arg_types = arg_info->types = void_list_node;
+ arg_info->c23_empty_parens = 1;
+ }
/* If there is a parameter of incomplete type in a definition,
this is an error. In a declaration this is valid, and a
@@ -8589,6 +8592,7 @@ build_arg_info (void)
ret->pending_sizes = NULL;
ret->had_vla_unspec = 0;
ret->no_named_args_stdarg_p = 0;
+ ret->c23_empty_parens = 0;
return ret;
}
@@ -10923,7 +10927,8 @@ store_parm_decls_newstyle (tree fndecl, const struct
c_arg_info *arg_info)
its parameter list). */
else if (!in_system_header_at (input_location)
&& !current_function_scope
- && arg_info->types != error_mark_node)
+ && arg_info->types != error_mark_node
+ && !arg_info->c23_empty_parens)
warning_at (DECL_SOURCE_LOCATION (fndecl), OPT_Wtraditional,
"traditional C rejects ISO C style function definitions");
diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index bfdcb78bbcc..a1435e7cb0c 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -525,6 +525,10 @@ struct c_arg_info {
BOOL_BITFIELD had_vla_unspec : 1;
/* True when the arguments are a (...) prototype. */
BOOL_BITFIELD no_named_args_stdarg_p : 1;
+ /* True when empty parentheses have been interpreted as (void) in C23 or
+ later. This is only for use by -Wtraditional and is no longer needed if
+ -Wtraditional is removed. */
+ BOOL_BITFIELD c23_empty_parens : 1;
};
/* A declarator. */
diff --git a/gcc/testsuite/gcc.dg/wtr-gnu17-1.c
b/gcc/testsuite/gcc.dg/wtr-gnu17-1.c
new file mode 100644
index 00000000000..74c06e4aa4c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/wtr-gnu17-1.c
@@ -0,0 +1,9 @@
+/* Test -Wtraditional -std=gnu17 does not warn for empty parentheses in
+ function definition. */
+/* { dg-do compile } */
+/* { dg-options "-Wtraditional -std=gnu17" } */
+
+void
+f ()
+{
+}
diff --git a/gcc/testsuite/gcc.dg/wtr-gnu23-1.c
b/gcc/testsuite/gcc.dg/wtr-gnu23-1.c
new file mode 100644
index 00000000000..207e7c59d27
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/wtr-gnu23-1.c
@@ -0,0 +1,9 @@
+/* Test -Wtraditional -std=gnu23 does not warn for empty parentheses in
+ function definition. */
+/* { dg-do compile } */
+/* { dg-options "-Wtraditional -std=gnu23" } */
+
+void
+f ()
+{
+}
--
Joseph S. Myers
josmy...@redhat.com
