Alternate Keywords
==================
The option `-traditional' disables certain keywords; `-ansi'
disables certain others. This causes trouble when you want to use GNU C
extensions, or ANSI C features, in a general-purpose header file that
should be usable by all programs, including ANSI C programs and
traditional ones. The keywords `asm', `typeof' and `inline' cannot be
used since they won't work in a program compiled with `-ansi', while
the keywords `const', `volatile', `signed', `typeof' and `inline' won't
work in a program compiled with `-traditional'.
The way to solve these problems is to put `__' at the beginning and
end of each problematical keyword. For example, use `__asm__' instead
of `asm', `__const__' instead of `const', and `__inline__' instead of
`inline'.
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' causes warnings for many GNU C extensions. You can
prevent such warnings within one expression by writing `__extension__'
before the expression. `__extension__' has no effect aside from this.