Lift the accept4 check

Summary: [Folly] Lift the `accept4` check to an explicit preprocessor symbol set at configure time.

Reviewed By: gkmhub

Differential Revision: D15802038

fbshipit-source-id: e85a258bb6650af42ab149b0bff4854196c3157d

CMake/FollyConfigChecks.cmake

@@ -70,6 +70,7 @@ check_symbol_exists(pthread_atfork pthread.h FOLLY_HAVE_PTHREAD_ATFORK)
 # Unfortunately check_symbol_exists() does not work for memrchr():
 # it fails complaining that there are multiple overloaded versions of memrchr()
 check_function_exists(memrchr FOLLY_HAVE_MEMRCHR)
+check_symbol_exists(accept4 sys/socket.h FOLLY_HAVE_ACCEPT4)
 check_symbol_exists(preadv sys/uio.h FOLLY_HAVE_PREADV)
 check_symbol_exists(pwritev sys/uio.h FOLLY_HAVE_PWRITEV)
 check_symbol_exists(clock_gettime time.h FOLLY_HAVE_CLOCK_GETTIME)

CMake/folly-config.h.cmake

@@ -43,10 +43,13 @@
 #endif
 
 #cmakedefine FOLLY_HAVE_MEMRCHR 1
+#cmakedefine FOLLY_HAVE_ACCEPT4 1
 #cmakedefine FOLLY_HAVE_PREADV 1
 #cmakedefine FOLLY_HAVE_PWRITEV 1
 #cmakedefine FOLLY_HAVE_CLOCK_GETTIME 1
 #cmakedefine FOLLY_HAVE_PIPE2 1
+#cmakedefine FOLLY_HAVE_SENDMMSG 1
+#cmakedefine FOLLY_HAVE_RECVMMSG 1
 #cmakedefine FOLLY_HAVE_OPENSSL_ASN1_TIME_DIFF 1
 
 #cmakedefine FOLLY_HAVE_IFUNC 1
@@ -78,5 +81,3 @@
 #cmakedefine01 FOLLY_LIBRARY_SANITIZE_ADDRESS
 
 #cmakedefine FOLLY_SUPPORT_SHARED_LIBRARY 1
-#cmakedefine FOLLY_HAVE_SENDMMSG 1
-#cmakedefine FOLLY_HAVE_RECVMMSG 1

folly/io/async/AsyncServerSocket.cpp

@@ -847,7 +847,7 @@ void AsyncServerSocket::handlerReady(
     }
 
     // Accept a new client socket
-#ifdef SOCK_NONBLOCK
+#if FOLLY_HAVE_ACCEPT4
     auto clientSocket = NetworkSocket::fromFd(
         accept4(fd.toFd(), saddr, &addrLen, SOCK_NONBLOCK));
 #else
@@ -942,7 +942,7 @@ void AsyncServerSocket::handlerReady(
       return;
     }
 
-#ifndef SOCK_NONBLOCK
+#if !FOLLY_HAVE_ACCEPT4
     // Explicitly set the new connection to non-blocking mode
     if (netops::set_socket_non_blocking(clientSocket) != 0) {
       closeNoInt(clientSocket);