POSIX_C_SOURCE

[Erik Trulsson]

On Sat, Aug 30, 2003 at 12:49:15PM -0400, Garrett Wollman wrote:
> In article <20030830161813.GA28890 at twisted.net> you write:
> 
> >Any chance that someone will finally commit the fixes to prevent the
> >POSIX_C_SOURCE warnings from showing up? I saw a number of posts on this
> >topic, but it still seems like it's not "officially committed"
> 
> >/usr/include/sys/cdefs.h:273: warning: `_POSIX_C_SOURCE' is not defined
> >/usr/include/sys/cdefs.h:279: warning: `_POSIX_C_SOURCE' is not defined
> 
> The warnings are wrong,[1] so you should probably ask the GCC people
> about that.

The warnings are not wrong (see below), but anyway, since -stable uses
the "ancient" GCC 2.95.4, the GCC people are not likely to
give a damn in either case.  They usually don't care about the older
releases.

> 
> -GAWollman
> 
> [1] That is to say, any identifier used in a preprocessor expression
> (after macro expansion) is defined to have a value of zero, and GCC
> should not be complaining about this.

The code is correct, which is why GCC only gives a warning and not an
error.  Code looking like that are usually an indication of a
programmer error though, so GCC is perfectly right in warning about
it.  This is similar to the compiler warning about unused variables,
which isn't a bug either but often indicates a programmer mistake.

To make gcc shut up, you can apply the following patch to cdefs.h
which makes the warnings go away, without changing the semantics of the
include file in any way.


Index: cdefs.h
===================================================================
RCS file: /ncvs/src/sys/sys/cdefs.h,v
retrieving revision 1.28.2.8
diff -u -r1.28.2.8 cdefs.h
--- cdefs.h	18 Sep 2002 04:05:13 -0000	1.28.2.8
+++ cdefs.h	29 Jan 2003 21:23:30 -0000
@@ -269,6 +269,8 @@
  * Our macros begin with two underscores to avoid namespace screwage.
  */
 
+#ifdef _POSIX_C_SOURCE
+
 /* Deal with IEEE Std. 1003.1-1990, in which _POSIX_C_SOURCE == 1. */
 #if _POSIX_C_SOURCE == 1
 #undef _POSIX_C_SOURCE		/* Probably illegal, but beyond caring now. */
@@ -280,6 +282,8 @@
 #undef _POSIX_C_SOURCE
 #define	_POSIX_C_SOURCE		199209
 #endif
+
+#endif /* _POSIX_C_SOURCE */
 
 /* Deal with various X/Open Portability Guides and Single UNIX Spec. */
 #ifdef _XOPEN_SOURCE




-- 
<Insert your favourite quote here.>
Erik Trulsson
ertr1013 at student.uu.se