PR c/23143

	* c-parser.c (c_parser_parms_list_declarator): Call
	mark_forward_parm_decls.
	* c-decl.c (merge_decls): Only check DECL_IN_SYSTEM_HEADER for
	decls with visibility structure.

testsuite:
	* gcc.dg/parm-forwdecl-1.c, gcc.dg/parm-forwdecl-2.c,
	gcc.dg/parm-forwdecl-3.c, gcc.dg/parm-forwdecl-4.c: New tests.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@102581 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 52 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.dg/parm-forwdecl-1.c b/gcc/testsuite/gcc.dg/parm-forwdecl-1.c
new file mode 100644
index 00000000000..470636de95c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/parm-forwdecl-1.c
@@ -0,0 +1,26 @@
+/* Test GNU parameter forward declarations.  */
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+/* Valid uses.  */
+int f1(int a; int a);
+int f2(int a; int a) { return 0; }
+int f3(int a; int a; int a);
+int f4(int a; int a; int a) { return 0; }
+int f5(int a; int (*x)[a], int a);
+int f6(int a; int (*x)[a], int a) { return 0; }
+int f7(int a; int (*x)[a]; int (*y)[x[1][2]], int (*x)[a], int a);
+int f8(int a; int (*x)[a]; int (*y)[x[1][2]], int (*x)[a], int a) { return 0; }
+
+/* Strange uses accepted by GCC 4.0 but not by 3.4 and probably not
+   desirable to accept.  */
+int g1(int a;); /* { dg-error "just a forward declaration" "no parms" { xfail *-*-* } } */
+int g2(int a; __attribute__((unused))); /* { dg-error "just a forward declaration" "no parms" { xfail *-*-* } } */
+int g3(int;); /* { dg-error "just a forward declaration" "no parms" { xfail *-*-* } } */
+int g4(int, long;); /* { dg-error "just a forward declaration" "no parms" { xfail *-*-* } } */
+
+/* Invalid uses.  */
+int h1(int a; int b); /* { dg-error "just a forward declaration" } */
+int h2(int; int b); /* { dg-error "just a forward declaration" } */
+int h3(int a; long a); /* { dg-error "conflicting types|previous definition|just a forward declaration" } */
diff --git a/gcc/testsuite/gcc.dg/parm-forwdecl-2.c b/gcc/testsuite/gcc.dg/parm-forwdecl-2.c
new file mode 100644
index 00000000000..cecedf2515c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/parm-forwdecl-2.c
@@ -0,0 +1,8 @@
+/* Test GNU parameter forward declarations.  Warning with
+   -pedantic.  */
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "-pedantic" } */
+
+int f1(int a; int a); /* { dg-warning "warning: ISO C forbids forward parameter declarations" } */
+int f2(int a; int a) { return 0; } /* { dg-warning "warning: ISO C forbids forward parameter declarations" } */
diff --git a/gcc/testsuite/gcc.dg/parm-forwdecl-3.c b/gcc/testsuite/gcc.dg/parm-forwdecl-3.c
new file mode 100644
index 00000000000..d99188a0bd4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/parm-forwdecl-3.c
@@ -0,0 +1,8 @@
+/* Test GNU parameter forward declarations.  Error with
+   -pedantic-errors.  */
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "-pedantic-errors" } */
+
+int f1(int a; int a); /* { dg-error "error: ISO C forbids forward parameter declarations" } */
+int f2(int a; int a) { return 0; } /* { dg-error "error: ISO C forbids forward parameter declarations" } */
diff --git a/gcc/testsuite/gcc.dg/parm-forwdecl-4.c b/gcc/testsuite/gcc.dg/parm-forwdecl-4.c
new file mode 100644
index 00000000000..a210092e1d5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/parm-forwdecl-4.c
@@ -0,0 +1,10 @@
+/* Test GNU parameter forward declarations.  OK with
+   -Wredundant-decls.  */
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "-Wredundant-decls" } */
+
+int f1(int a; int a);
+int f2(int a; int a) { return 0; }
+int f3(int a; int a; int a);
+int f4(int a; int a; int a) { return 0; }