re PR preprocessor/45038 (__DBL_MIN__ result in old-style-cast)

gcc/c-family/
	PR preprocessor/45038
	* c-cppbuiltin.c (c_cpp_builtins): Use different format for C++
	dialects.

gcc/testsuite/
	PR preprocessor/45038
	* g++.dg/pr45038.C: New test.

From-SVN: r166756

gcc/c-family/ChangeLog

+2010-11-15  Nathan Froyd  <froydnj@codesourcery.com>
+
+	PR preprocessor/45038
+	* c-cppbuiltin.c (c_cpp_builtins): Use different format for C++
+	dialects.
+
 2010-11-12  Joseph Myers  <joseph@codesourcery.com>
 
 	* c-common.h (c_family_lang_mask): Declare.

gcc/c-family/c-cppbuiltin.c

@@ -657,9 +657,13 @@ c_cpp_builtins (cpp_reader *pfile)
   /* Cast the double precision constants.  This is needed when single
      precision constants are specified or when pragma FLOAT_CONST_DECIMAL64
      is used.  The correct result is computed by the compiler when using
-     macros that include a cast.  */
-  builtin_define_float_constants ("DBL", "L", "((double)%s)", "",
-				  double_type_node);
+     macros that include a cast.  We use a different cast for C++ to avoid
+     problems with -Wold-style-cast.  */
+  builtin_define_float_constants ("DBL", "L",
+				  (c_dialect_cxx ()
+				   ? "double(%s)"
+				   : "((double)%s)"),
+				  "", double_type_node);
   builtin_define_float_constants ("LDBL", "L", "%s", "L",
 				  long_double_type_node);
 

gcc/testsuite/ChangeLog

+2010-11-15  Nathan Froyd  <froydnj@codesourcery.com>
+
+	PR preprocessor/45038
+	* g++.dg/pr45038.C: New test.
+
 2010-11-15  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/46467

gcc/testsuite/g++.dg/pr45038.C

+// PR preprocessor/45038
+// { dg-do compile }
+// { dg-options "-Werror -Wold-style-cast" }
+
+double f(void)
+{
+  // We used to produce old-style casts for this.
+  return __DBL_MIN__;
+}