Please describe the problem:
There is no S_ISREG in headers of Visual C++.
Please see the following bug-reports.
http://bugzilla.gnome.org/show_bug.cgi?id=156728
http://bugzilla.gnome.org/show_bug.cgi?id=158263

Steps to reproduce:
1. compile by Visual C++ 6.0

Actual results:
The following message is displayed.
gkeyfile.c(362) : error C4013: 'S_ISREG' undefined; assuming extern returning int

Expected results:
#156728 conflicts with #158263.
So, I suggest inserting the following macros to gstdio.h.

#ifdef S_IFMT
#define G_S_IFMT S_IFMT
#else
#define G_S_IFMT 0170000
#endif
#ifdef S_IFREG
#define G_S_IFREG S_IFREG
#else
#define G_S_IFREG 0100000
#endif
#ifdef S_IFDIR
#define G_S_IFDIR S_IFDIR
#else
#define G_S_IFDIR 0040000
#endif
#ifdef S_IFCHR
#define G_S_IFCHR S_IFCHR
#else
#define G_S_IFCHR 0020000
#endif
#ifdef S_IFBLK
#define G_S_IFBLK S_IFBLK
#else
#define G_S_IFBLK 0060000
#endif
#ifdef S_IFIFO
#define G_S_IFIFO S_IFIFO
#else
#define G_S_IFIFO 0010000
#endif
#ifdef S_IFLNK
#define G_S_IFLNK S_IFLNK
#else
#define G_S_IFLNK 0120000
#endif
#ifdef S_IFSOCK
#define G_S_IFSOCK S_IFSOCK
#else
#define G_S_IFSOCK 0140000
#endif

#ifdef S_ISREG
#define G_S_ISREG S_ISREG
#else
#define G_S_ISREG(m) (((m) & G_S_IFMT) == G_S_IFREG)
#endif
#ifdef S_ISDIR
#define G_S_ISDIR S_ISDIR
#else
#define G_S_ISDIR(m) (((m) & G_S_IFMT) == G_S_IFDIR)
#endif
#ifdef S_ISCHR
#define G_S_ISCHR S_ISCHR
#else
#define G_S_ISCHR(m) (((m) & G_S_IFMT) == G_S_IFCHR)
#endif
#ifdef S_ISBLK
#define G_S_ISBLK S_ISBLK
#else
#define G_S_ISBLK(m) (((m) & G_S_IFMT) == G_S_IFBLK)
#endif
#ifdef S_ISFIFO
#define G_S_ISFIFO S_ISFIFO
#else
#define G_S_ISFIFO(m) (((m) & G_S_IFMT) == G_S_IFIFO)
#endif
#ifdef S_ISLNK
#define G_S_ISLNK S_ISLNK
#else
#define G_S_ISLNK(m) (((m) & G_S_IFMT) == G_S_IFLNK)
#endif
#ifdef S_ISSOCK
#define G_S_ISSOCK S_ISSOCK
#else
#define G_S_ISSOCK(m) (((m) & G_S_IFMT) == G_S_IFSOCK)
#endif

Does this happen every time?
every time

Other information: