Example: Use of Predefined Macros in OS/2

version() is a routine from UnZip that prints as much compilation info as is known, based entirely on predefined compiler macros. Its output looks something like this:

Compiled with emx+gcc 2.5.8 for OS/2 2.x or 3.x (32-bit) on Jan 27 1995.

In the listing below, note that the Borland version numbers are probably wrong; they're based on the MS-DOS version of the compiler, which is why the debugging section is included at the end. The value of the __WATCOM__ variable is unknown, too. (Any and all information appreciated; please mail it to newt@pobox.com.)

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OS/2 version() routine:

void version()
{
 int len;
#if defined(__IBMC__) || defined(__WATCOMC__) || defined(_MSC_VER)
 char buf[80];
#endif
 len = sprintf((char *)slide, "Compiled with %s%s for %s%s%s%s.\n\n",
#ifdef __GNUC__
# ifdef __EMX__ /* __EMX__ is defined as "1" only (sigh) */
 "emx+gcc ", __VERSION__,
# else
 "gcc/2 ", __VERSION__,
# endif
#else
#ifdef __IBMC__
 "IBM C Set/2", (sprintf(buf, " %d.%02d", __IBMC__/100,__IBMC__%100), buf),
#else
#ifdef __WATCOMC__
 "Watcom C", (sprintf(buf, " (__WATCOMC__ = %d)", __WATCOMC__), buf),
#else
#ifdef __TURBOC__
# ifdef __BORLANDC__
 "Borland C++",
# if (__BORLANDC__ < 0x0200) " 1.0", # else # if (__BORLANDC__ == 0x0200) " 2.0", # else # if (__BORLANDC__ == 0x0400) " 3.0", # else # if (__BORLANDC__ == 0x0410) " 3.1", # else # if (__BORLANDC__ == 0x0452) " 4.0", # else /* these two are guesses based on DOS version */ # if (__BORLANDC__ == 0x0460) " 4.5", # else " later than 4.5", # endif # endif # endif # endif # endif # endif # else "Turbo C", # if (__TURBOC__>= 661)
 "++ 1.0 or later",
# else
# if (__TURBOC__ == 661)
 " 3.0?",
# else
# if (__TURBOC__ == 397)
 " 2.0",
# else
 " 1.0 or 1.5?",
# endif
# endif
# endif
# endif
#else
#ifdef MSC
 "Microsoft C ",
# ifdef _MSC_VER
 (sprintf(buf, "%d.%02d", _MSC_VER/100, _MSC_VER%100), buf),
# else
 "5.1 or earlier",
# endif
#else
 "unknown compiler", "",
#endif /* MSC */
#endif /* __TURBOC__ */
#endif /* __WATCOMC__ */
#endif /* __IBMC__ */
#endif /* __GNUC__ */
 "OS/2",
/* GRR: does IBM C/2 identify itself as IBM rather than Microsoft? */
#if (defined(MSC) || (defined(__WATCOMC__) && !defined(__386__)))
# if defined(M_I86HM) || defined(__HUGE__)
 " (16-bit, huge)",
# else
# if defined(M_I86LM) || defined(__LARGE__)
 " (16-bit, large)",
# else
# if defined(M_I86MM) || defined(__MEDIUM__)
 " (16-bit, medium)",
# else
# if defined(M_I86CM) || defined(__COMPACT__)
 " (16-bit, compact)",
# else
# if defined(M_I86SM) || defined(__SMALL__)
 " (16-bit, small)",
# else
# if defined(M_I86TM) || defined(__TINY__)
 " (16-bit, tiny)",
# else
 " (16-bit)",
# endif
# endif
# endif
# endif
# endif
# endif
#else
 " 2.x or 3.x (32-bit)",
#endif
#ifdef __DATE__
 " on ", __DATE__
#else
 "", ""
#endif
 );
 message(slide, (ulg)len, 0); /* MSC can't handle huge macro expansions */
 /* temporary debugging code for Borland compilers only */
#ifdef __TURBOC__
 Info(slide, 0, ((char *)slide, "\t(__TURBOC__ = 0x%04x = %d)\n", __TURBOC__,
 __TURBOC__));
#ifdef __BORLANDC__
 Info(slide, 0, ((char *)slide, "\t(__BORLANDC__ = 0x%04x)\n",__BORLANDC__));
#else
 Info(slide, 0, ((char *)slide, "\tdebug(__BORLANDC__ not defined)\n"));
#endif
#ifdef __TCPLUSPLUS__
 Info(slide, 0, ((char *)slide, "\t(__TCPLUSPLUS__ = 0x%04x)\n",
 __TCPLUSPLUS__));
#else
 Info(slide, 0, ((char *)slide, "\tdebug(__TCPLUSPLUS__ not defined)\n"));
#endif
#ifdef __BCPLUSPLUS__
 Info(slide, 0, ((char *)slide, "\t(__BCPLUSPLUS__ = 0x%04x)\n\n",
 __BCPLUSPLUS__));
#else
 Info(slide, 0, ((char *)slide, "\tdebug(__BCPLUSPLUS__ not defined)\n\n"));
#endif
#endif /* __TURBOC__ */
} /* end function version() */

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Click here to see UnZip's multi-compiler OS/2 makefile.
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Last modified 12 August 2000 by newt@pobox.com , you betcha.