configure: Improve check for built-in __atomic_* functions
authorTobias Brunner <tobias@strongswan.org>
Wed, 20 Jul 2016 09:01:17 +0000 (11:01 +0200)
committerTobias Brunner <tobias@strongswan.org>
Fri, 26 Aug 2016 07:59:01 +0000 (09:59 +0200)
commit6e19a1f5f203e932c634c6151d341b19b5420b44
treee196ab6adbf65f3288be321a0f8e70b041154164
parent1806ba0890bc503df3dacf01992ec1bca2b0fbb0
configure: Improve check for built-in __atomic_* functions

With AC_SEARCH_LIBS() we don't succeed if the searched function is a
built-in as the check uses the wrong signature so the built-in will not
be applied (the warning issued by GCC is "conflicting types for built-in
function '...'").  So even if not required, libatomic will be linked if
it is found, which could be problematic if compiling on a separate host
and the target host does not have libatomic installed.

Also, some tests showed that it's more likely that __atomic_and_fetch()
requires linking libatomic than __atomic_load_n() does.

References #1533.
configure.ac