c: Allow omitted parameter names for C2x

C2x allows parameter names to be omitted in function definitions, as
in C++; add support for this feature.  As with other features that
only result in previously rejected code being accepted, this feature
is now accepted as an extension for previous standard versions, with a
pedwarn-if-pedantic that is disabled by -Wno-c11-c2x-compat.  The
logic for avoiding unused-parameter warnings for unnamed parameters is
in code shared between C and C++, so no changes are needed there.

Bootstrapped with no regressions for x86_64-pc-linux-gnu.

gcc/c/
2020-10-28  Joseph Myers  <joseph@codesourcery.com>

	* c-decl.c (store_parm_decls_newstyle): Use pedwarn_c11 not
	error_at for omitted parameter name.

gcc/testsuite/
2020-10-28  Joseph Myers  <joseph@codesourcery.com>

	* gcc.dg/c11-parm-omit-1.c, gcc.dg/c11-parm-omit-2.c,
	gcc.dg/c11-parm-omit-3.c, gcc.dg/c11-parm-omit-4.c,
	gcc.dg/c2x-parm-omit-1.c, gcc.dg/c2x-parm-omit-2.c,
	gcc.dg/c2x-parm-omit-3.c, gcc.dg/c2x-parm-omit-4.c: New tests.
	* gcc.dg/noncompile/pr79758.c: Do not expect error for omitted
	parameter name.

diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 1673b9585550859cea170ef4bb94b35f0e72fff0..a5d0b158a26967878f51fac1dcbcea3b0f70ee3e 100644 (file)
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -9630,7 +9630,9 @@ store_parm_decls_newstyle (tree fndecl, const struct c_arg_info *arg_info)
            warn_if_shadowing (decl);
        }
       else
-       error_at (DECL_SOURCE_LOCATION (decl), "parameter name omitted");
+       pedwarn_c11 (DECL_SOURCE_LOCATION (decl), OPT_Wpedantic,
+                    "ISO C does not support omitting parameter names in "
+                    "function definitions before C2X");
     }
 
   /* Record the parameter list in the function declaration.  */

diff --git a/gcc/testsuite/gcc.dg/c11-parm-omit-1.c b/gcc/testsuite/gcc.dg/c11-parm-omit-1.c
new file mode 100644 (file)
index 0000000..83d1b50
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-parm-omit-1.c
@@ -0,0 +1,5 @@
+/* Test omitted parameter names not in C11: -pedantic-errors.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic-errors" } */
+
+void f (int) { } /* { dg-error "omitting parameter names" } */

diff --git a/gcc/testsuite/gcc.dg/c11-parm-omit-2.c b/gcc/testsuite/gcc.dg/c11-parm-omit-2.c
new file mode 100644 (file)
index 0000000..2efd450
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-parm-omit-2.c
@@ -0,0 +1,5 @@
+/* Test omitted parameter names not in C11: -pedantic.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic" } */
+
+void f (int) { } /* { dg-warning "omitting parameter names" } */

diff --git a/gcc/testsuite/gcc.dg/c11-parm-omit-3.c b/gcc/testsuite/gcc.dg/c11-parm-omit-3.c
new file mode 100644 (file)
index 0000000..5bf27a0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-parm-omit-3.c
@@ -0,0 +1,5 @@
+/* Test omitted parameter names not in C11: -pedantic -Wno-c11-c2x-compat.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic -Wno-c11-c2x-compat" } */
+
+void f (int) { }

diff --git a/gcc/testsuite/gcc.dg/c11-parm-omit-4.c b/gcc/testsuite/gcc.dg/c11-parm-omit-4.c
new file mode 100644 (file)
index 0000000..ea4cbfa
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-parm-omit-4.c
@@ -0,0 +1,6 @@
+/* Test omitted parameter names not in C11: accepted by default in the
+   absence of -pedantic.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11" } */
+
+void f (int) { }

diff --git a/gcc/testsuite/gcc.dg/c2x-parm-omit-1.c b/gcc/testsuite/gcc.dg/c2x-parm-omit-1.c
new file mode 100644 (file)
index 0000000..0dc89bb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-parm-omit-1.c
@@ -0,0 +1,5 @@
+/* Test omitted parameter names in C2x.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+void f (int) { }

diff --git a/gcc/testsuite/gcc.dg/c2x-parm-omit-2.c b/gcc/testsuite/gcc.dg/c2x-parm-omit-2.c
new file mode 100644 (file)
index 0000000..7d68933
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-parm-omit-2.c
@@ -0,0 +1,10 @@
+/* Test omitted parameter names in C2x.  Warning test: there should be
+   no warning for an unnamed parameter being unused.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -pedantic-errors -Wall -Wextra" } */
+
+int
+f (int a, int, int c, int d) /* { dg-warning "unused parameter 'd'" } */
+{
+  return a + c;
+}

diff --git a/gcc/testsuite/gcc.dg/c2x-parm-omit-3.c b/gcc/testsuite/gcc.dg/c2x-parm-omit-3.c
new file mode 100644 (file)
index 0000000..dac258b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-parm-omit-3.c
@@ -0,0 +1,23 @@
+/* Test omitted parameter names in C2x.  Execution test.  */
+/* { dg-do run } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+extern void abort (void);
+extern void exit (int);
+
+void
+f (int a, int [++a], int b)
+{
+  /* Verify array size expression of unnamed parameter is processed as
+     expected.  */
+  if (a != 2 || b != 3)
+    abort ();
+}
+
+int
+main (void)
+{
+  int t[2];
+  f (1, t, 3);
+  exit (0);
+}

diff --git a/gcc/testsuite/gcc.dg/c2x-parm-omit-4.c b/gcc/testsuite/gcc.dg/c2x-parm-omit-4.c
new file mode 100644 (file)
index 0000000..a4b0deb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-parm-omit-4.c
@@ -0,0 +1,5 @@
+/* Test omitted parameter names in C2x: diagnosed with -Wc11-c2x-compat.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -pedantic-errors -Wc11-c2x-compat" } */
+
+void f (int) { } /* { dg-warning "omitting parameter names" } */

diff --git a/gcc/testsuite/gcc.dg/noncompile/pr79758.c b/gcc/testsuite/gcc.dg/noncompile/pr79758.c
index aeaf7c71decdd23086293f72fa8bd636f3387e98..a31216068f002378cf6e120890695f143863088b 100644 (file)
--- a/gcc/testsuite/gcc.dg/noncompile/pr79758.c
+++ b/gcc/testsuite/gcc.dg/noncompile/pr79758.c
@@ -1,6 +1,6 @@
 /* PR c/79758 */
 /* { dg-do compile } */
 
-void fn1 (int[a]) { }; /* { dg-error "undeclared here|parameter name omitted" } */
+void fn1 (int[a]) { }; /* { dg-error "undeclared here" } */
 void fn1 (b) { }; /* { dg-error "redefinition" } */
 /* { dg-warning "defaults to 'int'" "" { target *-*-* } .-1 } */