configure.ac: fix check for futex and eventfd

We were using AC_LANG_PROGRAM to build a program to test for our ability
to call syscall (__NR_futex, ...);.  This macro adds "main () { ... }"
around the provided code segment automatically.  The provided code
segment provided its own main() function, however.

The result looked something like:

int main (void) {
  int main (void) {
    ...
  }
}

which worked on GCC, but not on clang.

Let's fix that.  Let's fix the same mistake copied over for eventfd()
detection while we're at it.

diff --git a/configure.ac b/configure.ac
index 6b6ab55..f5487fb 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -2386,13 +2386,7 @@ AC_CACHE_CHECK(for futex(2) system call,
 #include <sys/syscall.h>
 #include <unistd.h>
 ],[
-int
-main (void)
-{
-  /* it is not like this actually runs or anything... */
   syscall (__NR_futex, NULL, FUTEX_WAKE, FUTEX_WAIT);
-  return 0;
-}
 ])],glib_cv_futex=yes,glib_cv_futex=no))
 if test x"$glib_cv_futex" = xyes; then
   AC_DEFINE(HAVE_FUTEX, 1, [we have the futex(2) system call])
@@ -2403,12 +2397,7 @@ AC_CACHE_CHECK(for eventfd(2) system call,
 #include <sys/eventfd.h>
 #include <unistd.h>
 ],[
-int
-main (void)
-{
   eventfd (0, EFD_CLOEXEC);
-  return 0;
-}
 ])],glib_cv_eventfd=yes,glib_cv_eventfd=no))
 if test x"$glib_cv_eventfd" = x"yes"; then
   AC_DEFINE(HAVE_EVENTFD, 1, [we have the eventfd(2) system call])