Patch for PR 15749

["Joseph S. Myers" <jsm at polyomino dot org dot uk>]

Bug 15749 (a regression in 3.4 and 3.5) reports a problem with
-pedantic-errors rejecting glibc's <stdio.h> for flexible array
misuses.  The reason this didn't happen before 3.4 (although the
detection of these misuses went into 3.3) is that pedwarn_with_decl
didn't give any diagnostics in system headers at all, whereas with
-pedantic-errors pedwarns in system headers cause errors unless
there's a separate in_system_header check.  We may wish to revisit
this and cause pedwarn() not to give diagnostics in system headers at
all unless -Wsystem-headers (and also to revisit the various local
in_system_header checks on warnings or, after such a change, pedwarns,
that may predate -Wsystem-headers and the general disabling of
warnings in system headers by default), but the safe fix for 3.4
branch is clearly that below which adds local tests of
in_system_header to the pedwarns-if-pedantic for flexible array member
misuse.

Bootstrapped with no regressions on i686-pc-linux-gnu.  Applied to
mainline and 3.4 branch.

2004-05-31  Joseph S. Myers  <jsm@polyomino.org.uk>

	PR c/15749
	* c-decl.c (grokdeclarator, finish_struct): Don't pedwarn for
	misuses of structures with flexible array members if
	in_system_header.

testsuite:
2004-05-31  Joseph S. Myers  <jsm@polyomino.org.uk>

	PR c/15749
	* gcc.dg/pr15749-1.c, gcc.dg/pr15749-1.h: New test.

diff -rupN gcc.orig/c-decl.c gcc/c-decl.c
--- gcc.orig/c-decl.c	2004-03-24 10:52:04.000000000 +0000
+++ gcc/c-decl.c	2004-05-31 15:26:32.000000000 +0000
@@ -3832,7 +3832,7 @@ grokdeclarator (tree declarator, tree de
 	      type = error_mark_node;
 	    }
 
-	  if (pedantic && flexible_array_type_p (type))
+	  if (pedantic && !in_system_header && flexible_array_type_p (type))
 	    pedwarn ("invalid use of structure with flexible array member");
 
 	  if (size == error_mark_node)
@@ -5027,7 +5027,7 @@ finish_struct (tree t, tree fieldlist, t
 	    }
 	}
 
-      if (pedantic && TREE_CODE (t) == RECORD_TYPE
+      if (pedantic && !in_system_header && TREE_CODE (t) == RECORD_TYPE
 	  && flexible_array_type_p (TREE_TYPE (x)))
 	pedwarn ("%Jinvalid use of structure with flexible array member", x);
 
diff -rupN gcc.orig/testsuite/gcc.dg/pr15749-1.c gcc/testsuite/gcc.dg/pr15749-1.c
--- gcc.orig/testsuite/gcc.dg/pr15749-1.c	1970-01-01 00:00:00.000000000 +0000
+++ gcc/testsuite/gcc.dg/pr15749-1.c	2004-05-31 15:22:50.000000000 +0000
@@ -0,0 +1,8 @@
+/* Flexible array misuses (that are accepted without -pedantic) should
+   be OK in system headers even with -pedantic-errors.  PR 15749
+   from Tuomo dot Tikkanen at nokia dot com.  */
+/* Origin: Joseph Myers <jsm@polyomino.org.uk> */
+/* { dg-do compile } */
+/* { dg-options "-std=iso9899:1999 -pedantic-errors" } */
+
+#include "pr15749-1.h"
diff -rupN gcc.orig/testsuite/gcc.dg/pr15749-1.h gcc/testsuite/gcc.dg/pr15749-1.h
--- gcc.orig/testsuite/gcc.dg/pr15749-1.h	1970-01-01 00:00:00.000000000 +0000
+++ gcc/testsuite/gcc.dg/pr15749-1.h	2004-05-31 15:19:23.000000000 +0000
@@ -0,0 +1,28 @@
+/* Similar to c99-flex-array-3.c, but a system header so should not
+   have diagnostics even with -pedantic-errors.  */
+
+#pragma GCC system_header
+
+struct flex { int a; int b[]; };
+union rf1 { struct flex a; int b; };
+union rf2 { int a; struct flex b; };
+union rf3 { int a; union rf1 b; };
+union rf4 { union rf2 a; int b; };
+
+struct t0 { struct flex a; };
+struct t1 { union rf1 a; };
+struct t2 { union rf2 a; };
+struct t3 { union rf3 a; };
+struct t4 { union rf4 a; };
+
+void f0 (struct flex[]);
+void f1 (union rf1[]);
+void f2 (union rf2[]);
+void f3 (union rf3[]);
+void f4 (union rf4[]);
+
+struct flex a0[1];
+union rf1 a1[1];
+union rf2 a2[1];
+union rf3 a3[1];
+union rf4 a4[1];

-- 
Joseph S. Myers
jsm@polyomino.org.uk