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Re: Make bits/wchar.h correct for all architectures (bug 15036)


On Tue, 22 Jan 2013, Roland McGrath wrote:

> The substance of the change seems fine.  But the explanation for all the
> nonobvious elements belongs in comments in the file itself, not just in
> a posting here.

I've committed the patch in the following form, with an added comment.

diff --git a/ChangeLog b/ChangeLog
index 7d8eaf7..3d378c8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2013-01-23  Joseph Myers  <joseph@codesourcery.com>
+
+	[BZ #15036]
+	* bits/wchar.h (__WCHAR_MAX): Define based on __WCHAR_MAX__, or
+	based on [L'\0' - 1 > 0] if [!__WCHAR_MAX__].
+	(__WCHAR_MIN): Likewise, using __WCHAR_MIN__.
+	* sysdeps/unix/sysv/linux/x86/bits/wchar.h: Remove.
+
 2013-01-21  David S. Miller  <davem@davemloft.net>
 
 	* sysdeps/sparc/backtrace.c: New file.
diff --git a/NEWS b/NEWS
index abbbbae..9a039d8 100644
--- a/NEWS
+++ b/NEWS
@@ -10,7 +10,7 @@ Version 2.18
 * The following bugs are resolved with this release:
 
   13951, 14200, 14317, 14327, 14496, 14964, 14981, 14982, 14985, 14994,
-  14996, 15003, 15020, 15023.
+  14996, 15003, 15020, 15023, 15036.
 
 
 Version 2.17
diff --git a/bits/wchar.h b/bits/wchar.h
index eb07151..ef93d0e 100644
--- a/bits/wchar.h
+++ b/bits/wchar.h
@@ -19,7 +19,31 @@
 #ifndef _BITS_WCHAR_H
 #define _BITS_WCHAR_H	1
 
-#define __WCHAR_MIN	(-2147483647 - 1)
-#define __WCHAR_MAX	(2147483647)
+/* The fallback definitions, for when __WCHAR_MAX__ or __WCHAR_MIN__
+   are not defined, give the right value and type as long as both int
+   and wchar_t are 32-bit types.  Adding L'\0' to a constant value
+   ensures that the type is correct; it is necessary to use (L'\0' +
+   0) rather than just L'\0' so that the type in C++ is the promoted
+   version of wchar_t rather than the distinct wchar_t type itself.
+   Because wchar_t in preprocessor #if expressions is treated as
+   intmax_t or uintmax_t, the expression (L'\0' - 1) would have the
+   wrong value for WCHAR_MAX in such expressions and so cannot be used
+   to define __WCHAR_MAX in the unsigned case.  */
+
+#ifdef __WCHAR_MAX__
+# define __WCHAR_MAX	__WCHAR_MAX__
+#elif L'\0' - 1 > 0
+# define __WCHAR_MAX	(0xffffffffu + L'\0')
+#else
+# define __WCHAR_MAX	(0x7fffffff + L'\0')
+#endif
+
+#ifdef __WCHAR_MIN__
+# define __WCHAR_MIN	__WCHAR_MIN__
+#elif L'\0' - 1 > 0
+# define __WCHAR_MIN	(L'\0' + 0)
+#else
+# define __WCHAR_MIN	(-__WCHAR_MAX - 1)
+#endif
 
 #endif	/* bits/wchar.h */
diff --git a/sysdeps/unix/sysv/linux/x86/bits/wchar.h b/sysdeps/unix/sysv/linux/x86/bits/wchar.h
deleted file mode 100644
index 16b8b77..0000000
--- a/sysdeps/unix/sysv/linux/x86/bits/wchar.h
+++ /dev/null
@@ -1,32 +0,0 @@
-/* wchar_t type related definitions.  i386/x86-64 version.
-   Copyright (C) 2000-2013 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-#ifndef _BITS_WCHAR_H
-#define _BITS_WCHAR_H	1
-
-#include <bits/wordsize.h>
-
-#if __WORDSIZE == 64
-# define __WCHAR_MIN	(-2147483647 - 1)
-# define __WCHAR_MAX	(2147483647)
-#else
-# define __WCHAR_MIN	(-2147483647l - 1l)
-# define __WCHAR_MAX	(2147483647l)
-#endif
-
-#endif	/* bits/wchar.h */

-- 
Joseph S. Myers
joseph@codesourcery.com


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