That was introduced to fix bug 128853. I suppose I could use
_GNU_SOURCE, but I'd hoped to address the issue on non-glibc platforms
too.

That error doesn't make much sense to me (and is not in the headers on
the Solaris 9 box I just looked at). Are you using gcc? what happens
if you compile with -ansi?

I am using the Forte compiler on Solaris.  I am using a development
version of SolarisNext (the one that will be released after
Solaris 9).  So that is why the headers are different than what 
you see.   Forte supports these options:

-Xa             Compile assuming ANSI C conformance, allow K & R 
                extensions (default mode)
-Xc             Compile assuming strict ANSI C conformance
-Xs             Compile assuming (pre-ANSI) K & R C style code
-Xt             Compile assuming K & R conformance, allow ANSI C

I believe -Xa is the equilivant of -ansi for the gcc compiler.  I
tried using all of the above 4 options, and they all fail to compile.

If you want to #ifdef the logic so that it doesn't get used on 
Solaris, you could surround the #define with the following

#ifndef __SUNPRO_C
#endif

__SUNPRO_C is defined if you are compiling with Forte.

I'd rather try to figure out the right thing rather than do compiler
specific #ifdefs, especially since I don't know what will happen with gcc.

In limits.h (or wherever it is defined), what is the definition of
SSIZE_MAX guarded by?

Also, what is that #error guarded by?

The error is guarded by (from /usr/include/sys/feature_tests.h):

/*
 * It is invalid to compile an XPG3, XPG4, XPG4v2, or XPG5 application
 * using c99.  The same is true for POSIX.1-1990, POSIX.2-1992, POSIX.1b,
 * and POSIX.1c applications. Likewise, it is invalid to compile an XPG6
 * or a POSIX.1-2001 application with anything other than a c99 or later
 * compiler.  Therefore, we force an error in both cases.
 */
#if defined(_STDC_C99) && (defined(__XOPEN_OR_POSIX) && !defined(_XPG6))
#error "Compiler or options invalid for pre-UNIX 03 X/Open applications \
    and pre-2001 POSIX applications"
#elif !defined(_STDC_C99) && \
    (defined(__XOPEN_OR_POSIX) && defined(_XPG6))
#error "Compiler or options invalid; UNIX 03 and POSIX.1-2001
applications \
    require the use of c99"
#endif

----

SSIZE_MAX is guarded by:

#if defined(__EXTENSIONS__) || !defined(_STRICT_STDC) || \
    defined(__XOPEN_OR_POSIX)

#define SSIZE_MAX   LONG_MAX    /* max value of an "ssize_t" */

[..]
#endif /* defined(__EXTENSIONS__) || !defined(_STRICT_STDC) ... */

---

Hmm, it looks like with Solaris 9 headers and gcc -ansi, #define
_POSIX_SOURCE is needed as well, so papering it over with _GNU_SOURCE
instead won't work. Probably the same thing will happen on Solaris 10
once gcc's fixincludes is changed to recognize _STRICT_STDC.

I'm really not sure what to do here. What do the Sun docs recommend
for an app that is both POSIX-1.1990 and POSIX.1-2001 compliant?

It looks like we somehow need to get _XPG6 defined...

Brian, any progress on this front ? 
Is this still a problem ? 
Should we just close this bug ?

Yes, we work around this problem with Forte by adding a patch that says this just before the #include "config.h" in giounix.c

+#ifdef _STDC_C99
+#undef _STDC_C99
+#endif

Created attachment 135013 [details] [review]
Patch fixing the problem

Defining _XOPEN_SOURCE to 600 fixes the compilation problem.

I wonder if it is not redundant to define both _POSIX_SOURCE and _XOPEN_SOURCE. 

Doing some research on the patches that Sun applies, I see that we are not applying this patch anymore.  The patch was removed after glib was bumped to 2.12.4 in December 2006.  So I believe this issue was resolved via some other way.
I think this bug can just be closed.

thanks for the update