[Dvipng] dvipng and mmap preprocessor woes

[Karl Berry]

Hi Jan,

Vladimir discovered that dvipng/misc.c did not compile on AIX, where
mmap is a macro.  This interferes with its usage as a structure member
name in dvipng's struct filemmap.  (And this is allowed by C/POSIX
standards as far as I know -- my understanding is that basically any
"function" name can be a macro, as long as the result is addressable.)

Vladimir found a workaround (see patch and all the details below), but I
think the cleanest solution would be to simply rename the member field.
If you'd accept that, perhaps Vladimir or I could send you a patch for
that.  (Vladimir: meanwhile, I installed your change below.)

By the way, do you have any plans to make another dvipng release?  I'm
sorry for not writing earlier; I'd like to get the TeX Live tree to the
other builders as soon as possible.

Thanks,
Karl


Date: Sun, 27 Apr 2008 21:11:56 -0700
From: Vladimir Volovich <address@hidden>
To: address@hidden (Karl Berry)

[...]  what is happening is that texk/dvipng/misc.c #includes "dvipng.h"
which defines struct filemmap containing the field called "mmap".

then, misc.c includes <sys/mman.h>, which has "#define mmap mmap64",
so subsequent occurences of "mmap" get correctly translated to "mmap64".

but since "dvipng.h" was included prior to <sys/mman.h>, the "mmap"
field in "struct filemmap" was not affected by the "#define mmap
mmap64", which leads to inconsistency with later code which accesses the
"mmap" field (but because of "#define mmap mmap64" actually accesses
"mmap64" field).

so probably a better fix is to load "dvipng.h" after system headers,
ensuring that the same macros will apply to all code:

================================
--- texk/dvipng/misc.c
+++ texk/dvipng/misc.c
@@ -23,7 +23,6 @@
 
 ************************************************************************/
 
-#include "dvipng.h"
 #ifdef HAVE_LIBGEN_H
 # include <libgen.h>
 #else
@@ -34,6 +33,7 @@
 #include <sys/mman.h>
 #endif
 #include <sys/stat.h>
+#include "dvipng.h"
 
 static char *programname;
 
================================