re PR c/42439 (Linux kernel BUILD_BUG_ON() broke)

	PR c/42439
	* c-decl.c (check_bitfield_type_and_width): Only pedwarn if
	pedantic for bit-field width not an integer constant expression
	but folding to one.

testsuite:
	* gcc.dg/bitfld-19.c, gcc.dg/bitfld-20.c, gcc.dg/bitfld-21.c: New
	tests.

From-SVN: r155526

gcc/ChangeLog

+2009-12-30  Joseph Myers  <joseph@codesourcery.com>
+
+	PR c/42439
+	* c-decl.c (check_bitfield_type_and_width): Only pedwarn if
+	pedantic for bit-field width not an integer constant expression
+	but folding to one.
+
 2009-12-30  Ira Rosen  <irar@il.ibm.com>
 
 	PR tree-optimization/41956

gcc/c-decl.c

@@ -4570,14 +4570,26 @@ check_bitfield_type_and_width (tree *type, tree *width, tree orig_name)
 
   /* Detect and ignore out of range field width and process valid
      field widths.  */
-  if (!INTEGRAL_TYPE_P (TREE_TYPE (*width))
-      || TREE_CODE (*width) != INTEGER_CST)
+  if (!INTEGRAL_TYPE_P (TREE_TYPE (*width)))
     {
       error ("bit-field %qs width not an integer constant", name);
       *width = integer_one_node;
     }
   else
     {
+      if (TREE_CODE (*width) != INTEGER_CST)
+	{
+	  *width = c_fully_fold (*width, false, NULL);
+	  if (TREE_CODE (*width) == INTEGER_CST)
+	    pedwarn (input_location, OPT_pedantic,
+		     "bit-field %qs width not an integer constant expression",
+		     name);
+	}
+      if (TREE_CODE (*width) != INTEGER_CST)
+	{
+	  error ("bit-field %qs width not an integer constant", name);
+	  *width = integer_one_node;
+	}
       constant_expression_warning (*width);
       if (tree_int_cst_sgn (*width) < 0)
 	{

gcc/testsuite/ChangeLog

+2009-12-30  Joseph Myers  <joseph@codesourcery.com>
+
+	PR c/42439
+	* gcc.dg/bitfld-19.c, gcc.dg/bitfld-20.c, gcc.dg/bitfld-21.c: New
+	tests.
+
 2009-12-30  Ira Rosen  <irar@il.ibm.com>
 
 	PR tree-optimization/41956

gcc/testsuite/gcc.dg/bitfld-19.c

+/* Test for bit-field widths not integer constant expressions but
+   folding to integer constants: PR 42439.  */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+void
+f (void)
+{
+  const int m = 1;
+  ((void)(sizeof(struct { int i:!!m; })));
+}

gcc/testsuite/gcc.dg/bitfld-20.c

+/* Test for bit-field widths not integer constant expressions but
+   folding to integer constants: PR 42439.  */
+/* { dg-do compile } */
+/* { dg-options "-O2 -pedantic" } */
+
+void
+f (void)
+{
+  const int m = 1;
+  ((void)(sizeof(struct { int i:!!m; }))); /* { dg-warning "not an integer constant expression" } */
+}

gcc/testsuite/gcc.dg/bitfld-21.c

+/* Test for bit-field widths not integer constant expressions but
+   folding to integer constants: PR 42439.  */
+/* { dg-do compile } */
+/* { dg-options "-O2 -pedantic-errors" } */
+
+void
+f (void)
+{
+  const int m = 1;
+  ((void)(sizeof(struct { int i:!!m; }))); /* { dg-error "not an integer constant expression" } */
+}