-traditional disables certain keywords;
-ansi and the various
-std options disable certain
others. This causes trouble when you want to use GNU C extensions, or
ISO C features, in a general-purpose header file that should be usable
by all programs, including ISO C programs and traditional ones. The
inline cannot be used
since they won't work in a program compiled with
inline can be used in a program compiled with
-std=c99), while the keywords
inline won't work in a program
-traditional. The ISO C99 keyword
restrict is only available when
-std=gnu99 (which will
eventually be the default) or
-std=c99 (or the equivalent
-std=iso9899:1999) is used.
The way to solve these problems is to put
__ at the beginning and
end of each problematical keyword. For example, use
__const__ instead of
__inline__ instead of
Other C compilers won't accept these alternative keywords; if you want to compile with another compiler, you can define the alternate keywords as macros to replace them with the customary keywords. It looks like this:
#ifndef __GNUC__ #define __asm__ asm #endif
-pedantic and other options cause warnings for many GNU C extensions.
prevent such warnings within one expression by writing
__extension__ before the expression.
__extension__ has no
effect aside from this.