The autoconf documentation has this to say about the standard C headers:
On systems without ANSI C headers, there is so much variation that
it is probably easier to declare the functions you use than to
figure out exactly what the system header files declare. Some
systems contain a mix of functions ANSI and BSD; some are mostly
ANSI but lack `memmove'; some define the BSD functions as macros in
`string.h' or `strings.h'; some have only the BSD functions but
`string.h'; some declare the memory functions in `memory.h', some
in `string.h'; etc. It is probably sufficient to check for one
string function and one memory function; if the library has the
ANSI versions of those then it probably has most of the others.
If you put the following in `configure.in':
AC_HEADER_STDC
AC_CHECK_FUNCS(strchr memcpy)
then, in your code, you can put declarations like this:
#if STDC_HEADERS
# include <string.h>
#else
# ifndef HAVE_STRCHR
# define strchr index
# define strrchr rindex
# endif
char *strchr (), *strrchr ();
# ifndef HAVE_MEMCPY
# define memcpy(d, s, n) bcopy ((s), (d), (n))
# define memmove(d, s, n) bcopy ((s), (d), (n))
# endif
#endif
But autoconf itself doesn't do this; it instead goes to some lengths to
track down the appropriate headers and include them rather than using its
own prototypes. For example, see ac_include_default in acgeneral.m4.
Which is the right way of doing it?
--
Russ Allbery ([EMAIL PROTECTED]) <http://www.eyrie.org/~eagle/>
