>>>>> "Ian" == Ian Lance Taylor <[EMAIL PROTECTED]> writes:
Ian> The GNU binutils use this macro to detect this case:
Ian> dnl See whether we need a declaration for a function.
Ian> AC_DEFUN(BFD_NEED_DECLARATION,
There is something like this in Autoconf now:
Generic Declaration Checks
--------------------------
These macros are used to find declarations not covered by the
particular test macros.
- Macro: AC_CHECK_DECL (SYMBOL, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES])
If the declaration of SYMBOL (a function or a variable) is needed
because it is not declared in INCLUDES, run the shell commands
ACTION-IF-NOT-FOUND, otherwise ACTION-IF-FOUND. If no INCLUDES
are specified, the default includes are used (*note Default
Includes::).
This macro actually tests whether it is valid to use SYMBOL as an
r-value, not if it is really declared, because it is much safer to
avoid introducing extra declarations when not needed.
- Macro: AC_CHECK_DECLS ((SYMBOL, ...), [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES])
For each given SYMBOL (comma separated list), define
`HAVE_DECL_SYMBOL' (in all capitals) to `1' if SYMBOL is declared,
otherwise to `0'. If ACTION-IF-NOT-FOUND is given, it is
additional shell code to execute when one of the function
declarations is needed, otherwise ACTION-IF-FOUND is executed.
This macro uses an m4 list as first argument:
AC_CHECK_DECLS((strlen))
AC_CHECK_DECLS((malloc, realloc, calloc, free))
Unlike the other `AC_CHECK_*S' macros, when a SYMBOL is not
declared, `HAVE_DECL_SYMBOL' is defined to `0' instead of leaving
`HAVE_DECL_SYMBOL' undeclared.
When you are _sure_ that the check was performed, use
`HAVE_DECL_SYMBOL' just like any other result of Autoconf:
#if !HAVE_DECL_SYMBOL
extern char *symbol;
#endif
But if the test may have not been performed, because it is safer
_not_ to declare a symbol than to use a declaration which conflicts
with the system's one, you should use:
#if defined HAVE_DECL_MALLOC && !HAVE_DECL_MALLOC
char *malloc (size_t *s);
#endif
You fall into the second category only in extreme situations:
either your files may be used without being configured, or they
are used during the configuration. In most cases the traditional
approach is enough.
Akim
