Re: [RFC/PATCH 1/2] Teach Solaris that _XOPEN_SOURCE=600 really menas XPG6

Brandon Casey [off-list ref] writes:

So we either require compiling with a c99 compiler (by ensuring that
_XPG6 is set) or exclude compiling with a c99 compiler on sun (by
ensuring that _XPG6 is not set).  Actually, this would only affect Solaris
versions which support XPG6.  Solaris 11 and 10 do.  I don't know about
Solaris 9 and 8.  Solaris 7 doesn't.

Which do we want to do?

If possible, both ;-), because people would have or want to use different
compilers.

I use "gcc -std=c99" on all platforms I compile git on (for details see
"Make" in the 'todo' branch; I have a checkout of the todo branch at Meta/
and say "Meta/Make --pedantic" from the toplevel), and that is how I
noticed this breakage on OpenSolaris 08.11 (it identifies itself as 5.11,
so presumably it falls into "Solaris 11" category you cited above?)

quoted

diff --git a/git-compat-util.h b/git-compat-util.h
index c7cf2d5..4236647 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h

@@ -41,8 +41,10 @@
 
 #if !defined(__APPLE__) && !defined(__FreeBSD__)  && !defined(__USLC__) && !defined(_M_UNIX)
 #define _XOPEN_SOURCE 600 /* glibc2 and AIX 5.3L need 500, OpenBSD needs 600 for S_ISLNK() */

Judging from their header files, I guess Sun's attitude is incompatible
with the above comment for _XOPEN_SOURCE.  We say "... need 500" and set
it to 600 because we merely mean "need to be at least 500" by "need 500",
but Sun wants us to be very precise.  So instead of saying __sun__, we
could do something more explicit with a huge comment...

	#if !defined(__APPLE__) ...
        # define _XOPEN_SOURCE 600
        /*
         * On Solaris, when _XOPEN_EXTENDED is set, its header file
         * forces the programs to be XPG4v2, defeating the _XOPEN_SOURCE
         * setting we just made to say we are XPG6.  Also on Solaris,
         * XPG6 programs must be compiled with a c99 compiler, while
         * non XPG6 programs must be compiled with a pre-c99 compiler.
         */
        # if defined(__sun__) && !(__STDC_VERSION__ - 0 >= 199901L)
        # define _XOPEN_EXTENDED 1 /* AIX 5.3L wants this */
        # endif
	#endif

We might want to flatten this a bit more to special case Solaris, which
might make it easier to maintain, e.g.

	#if defined(__sun__)
        # ... whatever _XOPEN_SOURCE and _XOPEN_EXTENDED magic
        # ... Solaris wants
        #elif !defined(__APPLE__) && ...
        # ... existing code
        #endif