Check for WNOWAIT in waitpid() in runtime (not in cmake/configure)

Because checking in cmake breaks cross-compiling.

Introduced-in: 43eb56c.
Fixes: libevent#482
Fixes: libevent#462
Refs: libevent#475

v2: use waitid() with WNOWAIT
v3: use WNOWAIT only if it available in waitpid(), because not all netbsd
    supports it

CMakeLists.txt

@@ -492,8 +492,6 @@ CHECK_TYPE_SIZE("void *" EVENT__SIZEOF_VOID_P)
 #CHECK_FILE_OFFSET_BITS()
 #set(EVENT___FILE_OFFSET_BITS _FILE_OFFSET_BITS)
 
-include(CheckWaitpidSupportWNOWAIT)
-
 # Verify kqueue works with pipes.
 if (EVENT__HAVE_KQUEUE)
     if (CMAKE_CROSSCOMPILING AND NOT EVENT__FORCE_KQUEUE_CHECK)

configure.ac

@@ -599,26 +599,6 @@ main(int argc, char **argv)
 fi
 AM_CONDITIONAL(EPOLL_BACKEND, [test "x$haveepoll" = "xyes"])
 
-AC_MSG_CHECKING(waitpid support WNOWAIT)
-AC_TRY_RUN(
-#include <unistd.h>
-#include <sys/types.h>
-#include <sys/wait.h>
-#include <stdlib.h>
-
-int
-main(int argc, char** argv)
-{
-    pid_t pid;
-    int status;
-    if ((pid = fork()) == 0) _exit(0);
-    _exit(waitpid(pid, &status, WNOWAIT) == -1);
-}, [AC_MSG_RESULT(yes)
-AC_DEFINE(HAVE_WAITPID_WITH_WNOWAIT, 1,
-[Define if waitpid() supports WNOWAIT])
-], AC_MSG_RESULT(no), AC_MSG_RESULT(no))
-
-
 haveeventports=no
 AC_CHECK_FUNCS(port_create, [haveeventports=yes], )
 if test "x$haveeventports" = "xyes" ; then

event-config.h.cmake

@@ -526,7 +526,4 @@
 /* Define to 1 if you have ERR_remove_thread_stat(). */
 #cmakedefine EVENT__HAVE_ERR_REMOVE_THREAD_STATE
 
-/* Define if waitpid() supports WNOWAIT */
-#cmakedefine EVENT__HAVE_WAITPID_WITH_WNOWAIT
-
-#endif
+#endif /* \EVENT2_EVENT_CONFIG_H_INCLUDED_ */

test/regress.c

@@ -855,11 +855,6 @@ test_fork(void)
 	int status;
 	struct event ev, sig_ev, usr_ev, existing_ev;
 	pid_t pid;
-	int wait_flags = 0;
-
-#ifdef EVENT__HAVE_WAITPID_WITH_WNOWAIT
-	wait_flags |= WNOWAIT;
-#endif
 
 	setup_test("After fork: ");
 
@@ -934,7 +929,8 @@ test_fork(void)
 	}
 
 	TT_BLATHER(("Before waitpid"));
-	if (waitpid(pid, &status, wait_flags) == -1) {
+	if ((waitpid(pid, &status, WNOWAIT) == -1 && errno == EINVAL) &&
+	    waitpid(pid, &status, 0) == -1) {
 		perror("waitpid");
 		exit(1);
 	}