c: Remove restrictions on declarations in 'for' loops for C2X

C2X removes a restriction that the only declarations in the
declaration part of a 'for' loop are declarations of objects with
storage class auto or register.  Implement this change, making the
diagnostics into pedwarn_c11 calls instead of errors (as usual for
features added in a new standard version that were invalid code in a
previous version), so now pedwarn-if-pedantic for older standards and
diagnosed also with -Wc11-c2x-compat.

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

gcc/c/
	* c-decl.cc (check_for_loop_decls): Use pedwarn_c11 for
	diagnostics.

gcc/testsuite/
	* gcc.dg/c11-fordecl-1.c, gcc.dg/c11-fordecl-2.c,
	gcc.dg/c11-fordecl-3.c, gcc.dg/c11-fordecl-4.c,
	gcc.dg/c2x-fordecl-1.c, gcc.dg/c2x-fordecl-2.c,
	gcc.dg/c2x-fordecl-3.c, gcc.dg/c2x-fordecl-4.c: New tests.
	* gcc.dg/c99-fordecl-2.c: Test diagnostic for typedef declaration
	in for loop here.
	* gcc.dg/pr67784-2.c, gcc.dg/pr68320.c, objc.dg/foreach-7.m: Do
	not expect errors for typedef declaration in for loop.

13 files changed, 142 insertions, 30 deletions

diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 90d7cd27cd5..f8ede362bfd 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -11032,7 +11032,9 @@ check_for_loop_decls (location_t loc, bool turn_off_iso_c99_error)
      only applies to those that are.  (A question on this in comp.std.c
      in November 2000 received no answer.)  We implement the strictest
      interpretation, to avoid creating an extension which later causes
-     problems.  */
+     problems.
+
+     This constraint was removed in C2X.  */
 
   for (b = current_scope->bindings; b; b = b->prev)
     {
@@ -11048,33 +11050,35 @@ check_for_loop_decls (location_t loc, bool turn_off_iso_c99_error)
 	  {
 	    location_t decl_loc = DECL_SOURCE_LOCATION (decl);
 	    if (TREE_STATIC (decl))
-	      error_at (decl_loc,
-			"declaration of static variable %qD in %<for%> loop "
-			"initial declaration", decl);
+	      pedwarn_c11 (decl_loc, OPT_Wpedantic,
+			   "declaration of static variable %qD in %<for%> "
+			   "loop initial declaration", decl);
 	    else if (DECL_EXTERNAL (decl))
-	      error_at (decl_loc,
-			"declaration of %<extern%> variable %qD in %<for%> loop "
-			"initial declaration", decl);
+	      pedwarn_c11 (decl_loc, OPT_Wpedantic,
+			   "declaration of %<extern%> variable %qD in %<for%> "
+			   "loop initial declaration", decl);
 	  }
 	  break;
 
 	case RECORD_TYPE:
-	  error_at (loc,
-		    "%<struct %E%> declared in %<for%> loop initial "
-		    "declaration", id);
+	  pedwarn_c11 (loc, OPT_Wpedantic,
+		       "%<struct %E%> declared in %<for%> loop initial "
+		       "declaration", id);
 	  break;
 	case UNION_TYPE:
-	  error_at (loc,
-		    "%<union %E%> declared in %<for%> loop initial declaration",
-		    id);
+	  pedwarn_c11 (loc, OPT_Wpedantic,
+		       "%<union %E%> declared in %<for%> loop initial "
+		       "declaration",
+		       id);
 	  break;
 	case ENUMERAL_TYPE:
-	  error_at (loc, "%<enum %E%> declared in %<for%> loop "
-		    "initial declaration", id);
+	  pedwarn_c11 (loc, OPT_Wpedantic,
+		       "%<enum %E%> declared in %<for%> loop "
+		       "initial declaration", id);
 	  break;
 	default:
-	  error_at (loc, "declaration of non-variable "
-		    "%qD in %<for%> loop initial declaration", decl);
+	  pedwarn_c11 (loc, OPT_Wpedantic, "declaration of non-variable "
+		       "%qD in %<for%> loop initial declaration", decl);
 	}
 
       n_decls++;
diff --git a/gcc/testsuite/gcc.dg/c11-fordecl-1.c b/gcc/testsuite/gcc.dg/c11-fordecl-1.c
new file mode 100644
index 00000000000..4aceb335e18
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-fordecl-1.c
@@ -0,0 +1,27 @@
+/* Test for C99 declarations in for loops.  Test constraints are diagnosed for
+   C11.  Based on c99-fordecl-2.c.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic-errors" } */
+
+void
+foo (void)
+{
+  int j = 0;
+  for (int i = 1, bar (void); i <= 10; i++) /* { dg-error "bar" } */
+    j += i;
+
+  for (static int i = 1; i <= 10; i++) /* /* { dg-error "static" } */
+    j += i;
+
+  for (extern int i; j <= 500; j++) /* { dg-error "extern" } */
+    j += 5;
+
+  for (enum { FOO } i = FOO; i < 10; i++) /* { dg-error "FOO" } */
+    j += i;
+
+  for (enum BAR { FOO } i = FOO; i < 10; i++) /* { dg-error "FOO" } */
+    /* { dg-error "BAR" "enum tag in for loop" { target *-*-* } .-1 } */
+    j += i;
+  for (typedef int T;;) /* { dg-error "non-variable" } */
+    ;
+}
diff --git a/gcc/testsuite/gcc.dg/c11-fordecl-2.c b/gcc/testsuite/gcc.dg/c11-fordecl-2.c
new file mode 100644
index 00000000000..0be1a0d13fa
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-fordecl-2.c
@@ -0,0 +1,14 @@
+/* Test for C99 declarations in for loops.  Test constraints are diagnosed for
+   C11: struct and union tags can't be declared there (affirmed in response to
+   DR#277).  Based on c99-fordecl-3.c.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic-errors" } */
+
+void
+foo (void)
+{
+  for (struct s { int p; } *p = 0; ;) /* { dg-error "'struct s' declared in 'for' loop initial declaration" } */
+    ;
+  for (union u { int p; } *p = 0; ;) /* { dg-error "'union u' declared in 'for' loop initial declaration" } */
+    ;
+}
diff --git a/gcc/testsuite/gcc.dg/c11-fordecl-3.c b/gcc/testsuite/gcc.dg/c11-fordecl-3.c
new file mode 100644
index 00000000000..28ef6294c20
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-fordecl-3.c
@@ -0,0 +1,6 @@
+/* Test restrictions on the kind of declarations permitted in for loops removed
+   in C2X, and thus with -std=c11 -pedantic -Wno-c11-c2x-compat.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic -Wno-c11-c2x-compat" } */
+
+#include "c99-fordecl-2.c"
diff --git a/gcc/testsuite/gcc.dg/c11-fordecl-4.c b/gcc/testsuite/gcc.dg/c11-fordecl-4.c
new file mode 100644
index 00000000000..2a352d64963
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-fordecl-4.c
@@ -0,0 +1,6 @@
+/* Test restrictions on the kind of declarations permitted in for loops removed
+   in C2X, and thus with -std=c11 -pedantic -Wno-c11-c2x-compat.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic -Wno-c11-c2x-compat" } */
+
+#include "c99-fordecl-3.c"
diff --git a/gcc/testsuite/gcc.dg/c2x-fordecl-1.c b/gcc/testsuite/gcc.dg/c2x-fordecl-1.c
new file mode 100644
index 00000000000..563186f060b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-fordecl-1.c
@@ -0,0 +1,6 @@
+/* Test restrictions on the kind of declarations permitted in for loops removed
+   in C2X.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+#include "c99-fordecl-2.c"
diff --git a/gcc/testsuite/gcc.dg/c2x-fordecl-2.c b/gcc/testsuite/gcc.dg/c2x-fordecl-2.c
new file mode 100644
index 00000000000..42501901c3d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-fordecl-2.c
@@ -0,0 +1,6 @@
+/* Test restrictions on the kind of declarations permitted in for loops removed
+   in C2X.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+#include "c99-fordecl-3.c"
diff --git a/gcc/testsuite/gcc.dg/c2x-fordecl-3.c b/gcc/testsuite/gcc.dg/c2x-fordecl-3.c
new file mode 100644
index 00000000000..d39d4a6a4d7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-fordecl-3.c
@@ -0,0 +1,27 @@
+/* Test for C99 declarations in for loops.  Test constraints are diagnosed with
+   -Wc11-c2x-compat for C2X.  Based on c99-fordecl-2.c.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -pedantic-errors -Wc11-c2x-compat" } */
+
+void
+foo (void)
+{
+  int j = 0;
+  for (int i = 1, bar (void); i <= 10; i++) /* { dg-warning "bar" } */
+    j += i;
+
+  for (static int i = 1; i <= 10; i++) /* /* { dg-warning "static" } */
+    j += i;
+
+  for (extern int i; j <= 500; j++) /* { dg-warning "extern" } */
+    j += 5;
+
+  for (enum { FOO } i = FOO; i < 10; i++) /* { dg-warning "FOO" } */
+    j += i;
+
+  for (enum BAR { FOO } i = FOO; i < 10; i++) /* { dg-warning "FOO" } */
+    /* { dg-warning "BAR" "enum tag in for loop" { target *-*-* } .-1 } */
+    j += i;
+  for (typedef int T;;) /* { dg-warning "non-variable" } */
+    ;
+}
diff --git a/gcc/testsuite/gcc.dg/c2x-fordecl-4.c b/gcc/testsuite/gcc.dg/c2x-fordecl-4.c
new file mode 100644
index 00000000000..e9dfc4b51fa
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-fordecl-4.c
@@ -0,0 +1,14 @@
+/* Test for C99 declarations in for loops.  Test constraints are diagnosed with
+   -Wc11-c2x-compat for C2X: struct and union tags can't be declared there
+   (affirmed in response to DR#277).  Based on c99-fordecl-3.c.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -pedantic-errors -Wc11-c2x-compat" } */
+
+void
+foo (void)
+{
+  for (struct s { int p; } *p = 0; ;) /* { dg-warning "'struct s' declared in 'for' loop initial declaration" } */
+    ;
+  for (union u { int p; } *p = 0; ;) /* { dg-warning "'union u' declared in 'for' loop initial declaration" } */
+    ;
+}
diff --git a/gcc/testsuite/gcc.dg/c99-fordecl-2.c b/gcc/testsuite/gcc.dg/c99-fordecl-2.c
index aa5bc783ff8..a8d5b124fb6 100644
--- a/gcc/testsuite/gcc.dg/c99-fordecl-2.c
+++ b/gcc/testsuite/gcc.dg/c99-fordecl-2.c
@@ -29,4 +29,6 @@ foo (void)
     /* { dg-error "FOO" "enum value in for loop" { target *-*-* } .-1 } */
     /* { dg-error "BAR" "enum tag in for loop" { target *-*-* } .-2 } */
     j += i;
+  for (typedef int T;;) /* { dg-error "non-variable" } */
+    ;
 }
diff --git a/gcc/testsuite/gcc.dg/pr67784-2.c b/gcc/testsuite/gcc.dg/pr67784-2.c
index de3b1c89a89..07af9cbcb82 100644
--- a/gcc/testsuite/gcc.dg/pr67784-2.c
+++ b/gcc/testsuite/gcc.dg/pr67784-2.c
@@ -7,7 +7,7 @@ int T;
 void
 fn1 (void)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
       ;
   T *x; /* { dg-error "undeclared" } */
@@ -16,7 +16,7 @@ fn1 (void)
 void
 fn2 (void)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
       T = 1; /* { dg-error "expected expression" } */
   T *x; /* { dg-error "undeclared" } */
@@ -25,7 +25,7 @@ fn2 (void)
 void
 fn3 (void)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
       {
       }
@@ -35,7 +35,7 @@ fn3 (void)
 void
 fn4 (void)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
 L:
       ;
@@ -45,7 +45,7 @@ L:
 void
 fn5 (void)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
       ;
     else
diff --git a/gcc/testsuite/gcc.dg/pr68320.c b/gcc/testsuite/gcc.dg/pr68320.c
index 7060af8993e..5d891b9bb1e 100644
--- a/gcc/testsuite/gcc.dg/pr68320.c
+++ b/gcc/testsuite/gcc.dg/pr68320.c
@@ -5,7 +5,7 @@
 void
 fn1 (void)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
       ;
   T x; /* { dg-error "unknown type name" } */
@@ -14,7 +14,7 @@ fn1 (void)
 void
 fn2 (int i)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
       i = 5;
   T x; /* { dg-error "unknown type name" } */
@@ -23,7 +23,7 @@ fn2 (int i)
 void
 fn3 (void)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
       {
       }
@@ -33,7 +33,7 @@ fn3 (void)
 void
 fn4 (void)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
       ;
   T, T; /* { dg-error "undeclared" } */
@@ -42,7 +42,7 @@ fn4 (void)
 void
 fn5 (void)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
       ;
   T = 10; /* { dg-error "undeclared" } */
@@ -51,7 +51,7 @@ fn5 (void)
 void
 fn6 (void)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
       ;
   T[0]; /* { dg-error "undeclared" } */
@@ -60,7 +60,7 @@ fn6 (void)
 void
 fn7 (void)
 {
-  for (typedef int T;;) /* { dg-error "declaration of non-variable" } */
+  for (typedef int T;;)
     if (1)
       ;
   T (); /* { dg-warning "implicit declaration" } */
diff --git a/gcc/testsuite/objc.dg/foreach-7.m b/gcc/testsuite/objc.dg/foreach-7.m
index 7ceff075016..c8e817f258c 100644
--- a/gcc/testsuite/objc.dg/foreach-7.m
+++ b/gcc/testsuite/objc.dg/foreach-7.m
@@ -39,7 +39,7 @@ int main (void)
   id array = nil;
   id object = nil;
 
-  for (typedef int my_typedef in array) /* { dg-error "declaration of non-variable" } */
+  for (typedef int my_typedef in array)
     ;                                   /* { dg-error "iterating variable in fast enumeration is not an object" "" { target *-*-* } .-1 } */
 
   for (function () in nil) /* { dg-error "invalid iterating variable in fast enumeration" } */