June 1994
Intermediate to advanced
821 pages
24h 40m
English
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15.10 ANSI-C and POSIX Portability
The MIT Release 5 X distribution is compliant with ANSI-C and POSIX standards, and portable across a wide variety of platforms. While the goal of the ANSI-C and POSIX standards is portability, many systems do not implement these standards, or do not implement them fully, so the MIT R5 distribution defines new header files that attempt to mask the differences between systems. The header files are <X11/Xfuncproto.h>, <X11/Xfuncs.h>, <X11/Xosdefs.h>, and <X11/Xos.h>. None of these files are part of the official R5 standard, so they may not be shipped with your system. But they can be very useful in writing portable applications, so we have included them with the code from this book, which you can get as described in the Preface.[57]
15.10.1 <X11/Xosdefs.h>
The file <X11/Xosdefs.h> defines
symbols that describe a system’s support for ANSI-C and POSIX. Symbols
that describe a system’s support for other standards may be added in
the future. It defines two new symbols,
X_NOT_STDC_ENV and X_NOT_POSIX,
for systems that do not have the ANSI-C and POSIX header files,
respectively. When standard header files exist, your code should
include them. On systems which do not have them, however, attempting
to include them would cause a compilation error. The symbols in
<X11/Xosdefs.h> allow you to write code
that takes the right action in either situation. Note that
X_NOT_STDC_ENV is different from
__STDC__, which simply indicates whether or not the compiler supports ...