Problem: accept4 not available on all platforms

Solution: check for availability in CMake and autoconf before using it

CMakeLists.txt

@@ -236,6 +236,10 @@ set (CMAKE_REQUIRED_INCLUDES stdlib.h)
 check_function_exists (mkdtemp HAVE_MKDTEMP)
 set (CMAKE_REQUIRED_INCLUDES)
 
+set (CMAKE_REQUIRED_INCLUDES sys/socket.h)
+check_function_exists (accept4 HAVE_ACCEPT4)
+set (CMAKE_REQUIRED_INCLUDES)
+
 add_definitions (-D_REENTRANT -D_THREAD_SAFE)
 add_definitions (-DZMQ_CUSTOM_PLATFORM_HPP)
 

NEWS

@@ -212,6 +212,9 @@
 
 * Fixed #2809 - optimize select() usage on Windows
 
+* Fixed #2816 - add CMake and autoconf check for accept4, as it is not
+  available on old Linux releases, and fallback to accept + FD_CLOEXEC
+
 * Fixed #2824 - ZMQ_REQ socket does not report ZMQ_POLLOUT when ZMQ_REQ_RELAXED
   is set
 

builds/cmake/platform.hpp.in

@@ -36,6 +36,7 @@
 #cmakedefine ZMQ_HAVE_PTHREAD_SETNAME_2
 #cmakedefine ZMQ_HAVE_PTHREAD_SETNAME_3
 #cmakedefine ZMQ_HAVE_PTHREAD_SET_NAME
+#cmakedefine HAVE_ACCEPT4
 
 #cmakedefine ZMQ_HAVE_OPENPGM
 #cmakedefine ZMQ_MAKE_VALGRIND_HAPPY

builds/gyp/platform.hpp

@@ -71,6 +71,7 @@
 #   define ZMQ_HAVE_UIO 1
 #   define HAVE_CLOCK_GETTIME 1
 #   define HAVE_FORK 1
+#   define HAVE_ACCEPT4 1
 
 #else
 #   error "No platform defined, abandoning"

configure.ac

@@ -621,7 +621,7 @@ AC_LANG_POP([C++])
 
 # Checks for library functions.
 AC_TYPE_SIGNAL
-AC_CHECK_FUNCS(perror gettimeofday clock_gettime memset socket getifaddrs freeifaddrs fork posix_memalign mkdtemp)
+AC_CHECK_FUNCS(perror gettimeofday clock_gettime memset socket getifaddrs freeifaddrs fork posix_memalign mkdtemp accept4)
 AC_CHECK_HEADERS([alloca.h])
 
 # pthread_setname is non-posix, and there are at least 4 different implementations

src/ipc_listener.cpp

@@ -382,7 +382,7 @@ zmq::fd_t zmq::ipc_listener_t::accept ()
     //  The situation where connection cannot be accepted due to insufficient
     //  resources is considered valid and treated by ignoring the connection.
     zmq_assert (s != retired_fd);
-#if defined ZMQ_HAVE_SOCK_CLOEXEC
+#if defined ZMQ_HAVE_SOCK_CLOEXEC && defined HAVE_ACCEPT4
     fd_t sock = ::accept4 (s, NULL, NULL, SOCK_CLOEXEC);
 #else
     fd_t sock = ::accept (s, NULL, NULL);
@@ -394,7 +394,7 @@ zmq::fd_t zmq::ipc_listener_t::accept ()
         return retired_fd;
     }
 
-#if !defined ZMQ_HAVE_SOCK_CLOEXEC && defined FD_CLOEXEC
+#if (!defined ZMQ_HAVE_SOCK_CLOEXEC || !defined HAVE_ACCEPT4) && defined FD_CLOEXEC
     //  Race condition can cause socket not to be closed (if fork happens
     //  between accept and this point).
     int rc = fcntl (sock, F_SETFD, FD_CLOEXEC);

src/tcp_listener.cpp

@@ -281,7 +281,7 @@ zmq::fd_t zmq::tcp_listener_t::accept ()
 #else
     socklen_t ss_len = sizeof (ss);
 #endif
-#if defined ZMQ_HAVE_SOCK_CLOEXEC
+#if defined ZMQ_HAVE_SOCK_CLOEXEC && defined HAVE_ACCEPT4
     fd_t sock = ::accept4 (s, (struct sockaddr *) &ss, &ss_len, SOCK_CLOEXEC);
 #else
     fd_t sock = ::accept (s, (struct sockaddr *) &ss, &ss_len);
@@ -311,7 +311,7 @@ zmq::fd_t zmq::tcp_listener_t::accept ()
     }
 #endif
 
-#if !defined ZMQ_HAVE_SOCK_CLOEXEC && defined FD_CLOEXEC
+#if (!defined ZMQ_HAVE_SOCK_CLOEXEC || !defined HAVE_ACCEPT4) && defined FD_CLOEXEC
     //  Race condition can cause socket not to be closed (if fork happens
     //  between accept and this point).
     int rc = fcntl (sock, F_SETFD, FD_CLOEXEC);