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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...)
Like calling AC_CHECK_FUNCS using an action-if-not-found that adds `function.o' to the value of the output variable LIBOBJS. You can declare a function for which your replacement version is used by enclosing the prototype in `#ifndef HAVE_function'. If the system has the function, it probably declares it in a header file you should be including, so you shouldn't redeclare it, lest your declaration conflict.

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