build: add check for pipe2

pipe2 is already used unconditionally in start-stop-deamon for
quite some time now.

Ref: #626

Author: N-R-K

meson.build

@@ -185,6 +185,14 @@ if cc.has_function('strlcpy', prefix: '#define _GNU_SOURCE\n#include <string.h>'
   add_project_arguments('-DHAVE_STRLCPY', language: 'c')
 endif
 
+if not cc.has_function('pipe2', prefix: '#include <unistd.h>')
+  if cc.has_function('pipe2', prefix: '#define _GNU_SOURCE\n#include <unistd.h>')
+    add_project_arguments('-D_GNU_SOURCE', language: 'c')
+  else
+    error('pipe2() not supported')
+  endif
+endif
+
 incdir = include_directories('src/shared')
 einfo_incdir = include_directories('src/libeinfo')
 rc_incdir = include_directories('src/librc')

src/openrc-init/openrc-init.c

@@ -26,12 +26,12 @@
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
+#include <fcntl.h>
 #include <unistd.h>
 #include <sys/stat.h>
 #include <sys/reboot.h>
 #include <sys/types.h>
 #include <sys/wait.h>
-#include <fcntl.h>
 #include <poll.h>
 #include <utmp.h>
 
@@ -266,15 +266,8 @@ int main(int argc, char **argv)
 		reexec = true;
 
 
-	/* NOTE(NRK): consider using pipe2 maybe... */
-	if (pipe(sigpipe) == -1) {
-		perror("pipe");
-		return 1;
-	}
-	if (fcntl(sigpipe[0], F_SETFD, O_NONBLOCK | FD_CLOEXEC) == -1 ||
-	    fcntl(sigpipe[1], F_SETFD, O_NONBLOCK | FD_CLOEXEC) == -1)
-	{
-		perror("fcntl");
+	if (pipe2(sigpipe, O_NONBLOCK | O_CLOEXEC) == -1) {
+		perror("pipe2");
 		return 1;
 	}