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).
AC_CHECK_FUNCSinstead. This macro checks for functions with C linkage even when
AC_LANG_CPLUSPLUShas been called, since C++ is more standardized than C is. (see section Language Choice, for more information about selecting the language for checks.)
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.
AC_CHECK_FUNCSusing 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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