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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 6. Writing Tests).
AC_CHECK_FUNCS
instead. This macro checks for functions with C
linkage even when AC_LANG(C++)
has been called, since C is more
standardized than C++. (see section 6.7 Language Choice, for more information
about selecting the language for checks.)
HAVE_function
(in all capitals) if it is available.
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.
Autoconf follows a philosophy that was formed over the years by those who have struggled for portability: isolate the portability issues in specific files, and then program as if you were in a POSIX environment. Some functions may be missing or unfixable, and your package must be ready to replace them.
Use the first three of the following macros to specify a function to be
replaced, and the last one (AC_REPLACE_FUNCS
) to check for and
replace the function if needed.
Technically, it adds `function.$ac_objext' to the output
variable LIBOBJS
and calls AC_LIBSOURCE
for
`function.c'. You should not directly change LIBOBJS
,
since this is not traceable.
AC_LIBSOURCE
. file must be a literal.
This macro is called automatically from AC_LIBOBJ
, but you must
call it explicitly if you pass a shell variable to AC_LIBOBJ
. In
that case, since shell variables cannot be traced statically, you must
pass to AC_LIBSOURCE
any possible files that the shell variable
might cause AC_LIBOBJ
to need. For example, if you want to pass
a variable $foo_or_bar
to AC_LIBOBJ
that holds either
"foo"
or "bar"
, you should do:
AC_LIBSOURCE(foo.c) AC_LIBSOURCE(bar.c) AC_LIBOBJ($foo_or_bar) |
There is usually a way to avoid this, however, and you are encouraged to
simply call AC_LIBOBJ
with literal arguments.
Note that this macro replaces the obsolete AC_LIBOBJ_DECL
, with
slightly different semantics: the old macro took the function name,
e.g. foo
, as its argument rather than the file name.
AC_LIBSOURCE
, but accepts one or more files in a
comma-separated M4 list. Thus, the above example might be rewritten:
AC_LIBSOURCES([foo.c, bar.c]) AC_LIBOBJ($foo_or_bar) |
AC_CHECK_FUNCS
, but uses `AC_LIBOBJ(function)' as
action-if-not-found. You can declare your replacement function by
enclosing the prototype in `#if !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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