Generic Function Checks

These macros are used to find functions not covered by the particular test macros. If the functions might be in libraries other than the default C library, first call AC_CHECK_LIB for those libraries. If you need to check the behavior of a function as well as find out whether it is present, you have to write your own test for it (see section Writing Tests).

Macro: AC_CHECK_FUNC (function, [action-if-found [, action-if-not-found]])

If C function function is available, run shell commands action-if-found, otherwise action-if-not-found. If you just want to define a symbol if the function is available, consider using AC_CHECK_FUNCS instead. This macro checks for functions with C linkage even when AC_LANG_CPLUSPLUS has been called, since C++ is more standardized than C is. (see section Language Choice, for more information about selecting the language for checks.)

Macro: AC_CHECK_FUNCS (function... [, action-if-found [, action-if-not-found]])

For each given function in the whitespace-separated argument list that is available, define HAVE_function (in all capitals). If action-if-found is given, it is additional shell code to execute when one of the functions is found. You can give it a value of `break' to break out of the loop on the first match. If action-if-not-found is given, it is executed when one of the functions is not found.

Macro: AC_REPLACE_FUNCS (function-name...)

For each given function-name in the whitespace-separated argument list that is not in the C library, add `function-name.o' to the value of the output variable LIBOBJS.