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These macros are used to find system header files not covered by the "particular" test macros. If you need to check the contents of a header as well as find out whether it is present, you have to write your own test for it (see section 6. Writing Tests).
AC_CHECK_HEADERS
instead.
The meaning of "usable" depends upon the content of includes:
header-file |
can be preprocessed without error.
includes #include <header-file> |
can be compiled without error. You may use
AC_CHECK_HEADER
(and AC_CHECK_HEADERS
) to check whether
two headers are compatible.
You may pass any kind of dummy content for includes, such as a single space, a comment, to check whether header-file compiles with success.
HAVE_header-file
(in all capitals). If action-if-found
is given, it is additional shell code to execute when one of the header
files 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 header files is not found.
Be sure to read the documentation of AC_CHECK_HEADER
to
understand the influence of includes.
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