Re: Why AC_C_CHAR_UNSIGNED?

[Eric Blake]

Eric Blake <ebb9 <at> byu.net> writes:
> According to Ralf Wildenhues on 8/3/2008 11:53 PM:
> | No.  The macro is not broken, don't fix it.  When you receive a bug
> | report about a system where it is problematic, then fix it.  Until
> | then, all you're doing is making life harder for users.
> 
> I think the verdict is in.  AC_C_CHAR_UNSIGNED will not be obsoleted in
> 2.63, unless someone points to a platform where the current implementation
> gets it wrong.  However, I am still open to a doc patch that mentions the
> alternative of CHAR_MIN.

Here's what I'm committing.  [I've also done a commit to resync various 
upstream files, such as GNUmakefile].

From: Eric Blake <address@hidden>
Date: Wed, 6 Aug 2008 09:24:09 -0600
Subject: [PATCH] AC_C_CHAR_UNSIGNED is not strictly necessary.

* doc/autoconf.texi (C Compiler) <AC_C_CHAR_UNSIGNED>: Mention a
portable alternative to this macro.
* THANKS: Update.
Reported by Hallvard B Furuseth.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog         |    6 ++++++
 THANKS            |    1 +
 doc/autoconf.texi |   11 +++++++++++
 3 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 155637b..ed7a915 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2008-08-06  Eric Blake  <address@hidden>
 
+       AC_C_CHAR_UNSIGNED is not strictly necessary.
+       * doc/autoconf.texi (C Compiler) <AC_C_CHAR_UNSIGNED>: Mention a
+       portable alternative to this macro.
+       * THANKS: Update.
+       Reported by Hallvard B Furuseth.
+
        Update some files from upstream.
        * GNUmakefile: Update.
        * build-aux/announce-gen: Likewise.
diff --git a/THANKS b/THANKS
index 912ec2c..7b903a9 100644
--- a/THANKS
+++ b/THANKS
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index b1b2a24..61cccca 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -6884,6 +6884,17 @@ if it accepts one of those, otherwise define @code
{inline} to be empty.
 @cvindex __CHAR_UNSIGNED__
 If the C type @code{char} is unsigned, define @code{__CHAR_UNSIGNED__},
 unless the C compiler predefines it.
+
+These days, using this macro is not necessary.  The same information can
+be determined by this portable alternative, thus avoiding the use of
+preprocessor macros in the namespace reserved for the implementation.
+
address@hidden
+#include <limits.h>
+#if CHAR_MIN == 0
+# define CHAR_UNSIGNED 1
+#endif
address@hidden example
 @end defmac
 
 @defmac AC_C_STRINGIZE
-- 
1.5.6.4