Add a wchar effective target to the testsuite

[Richard Sandiford <richard at codesourcery dot com>]

This patch adds an effective target for testing whether the runtime
has wide character support.  It's usually enough to check whether
<wchar.h> exists, but on uClibc targets, you also need to check
whether __UCLIBC_HAS_WCHAR__ is defined; if it isn't, the header
will still exist but will not be usable.

Tested on m68k-uclinux, i586-wrs-vxworks (which has no wchar.h)
and x86_64-linux-gnu.  OK to install?

Richard


gcc/testsuite/
	* lib/target-supports.exp (check_missing_uclibc_feature)
	(check_effective_target_wchar): New procedures.
	* gcc.dg/wchar_t-1.c: Require target wchar.
	* gcc.dg/wint_t-1.c: Likewise.

Index: gcc/testsuite/lib/target-supports.exp
===================================================================
--- gcc/testsuite/lib/target-supports.exp	(revision 122923)
+++ gcc/testsuite/lib/target-supports.exp	(working copy)
@@ -2065,6 +2065,21 @@ proc check_effective_target_uclibc {} {
     }]
 }
 
+# Return true if this is a uclibc target and if the uclibc feature
+# described by __$feature__ is not present.
+
+proc check_missing_uclibc_feature {feature} {
+    if {[check_no_compiler_messages $feature object "
+	     #include <features.h>
+	     #if defined (__UCLIBC__) && !defined (__${feature}__)
+	     #error FOO
+	     #endif
+	 "]} {
+	return 0
+    }
+    return 1
+}
+
 # Return true if this is a Newlib target.
 
 proc check_effective_target_newlib {} {
@@ -2197,3 +2212,14 @@ proc check_effective_target_vxworks_kern
 	#endif
     }]
 }
+
+# Return 1 if the target is expected to provide wide character support.
+
+proc check_effective_target_wchar { } {
+    if {[check_missing_uclibc_feature UCLIBC_HAS_WCHAR]} {
+	return 0
+    }
+    return [check_no_compiler_messages wchar assembly {
+	#include <wchar.h>
+    }]
+}
Index: gcc/testsuite/gcc.dg/wchar_t-1.c
===================================================================
--- gcc/testsuite/gcc.dg/wchar_t-1.c	(revision 122923)
+++ gcc/testsuite/gcc.dg/wchar_t-1.c	(working copy)
@@ -1,4 +1,4 @@
-/* { dg-do compile } */
+/* { dg-do compile { target wchar } } */
 /* { dg-options "-Wall" } */
 
 /* Compile with -Wall to get a warning if built-in and system wchar_t don't
Index: gcc/testsuite/gcc.dg/wint_t-1.c
===================================================================
--- gcc/testsuite/gcc.dg/wint_t-1.c	(revision 122923)
+++ gcc/testsuite/gcc.dg/wint_t-1.c	(working copy)
@@ -1,4 +1,4 @@
-/* { dg-do compile } */
+/* { dg-do compile { target wchar } } */
 /* { dg-options "-Wall" } */
 
 /* Compile with -Wall to get a warning if built-in and system wint_t don't