opal/util/fd.c: add new convenience function for setting FD_CLOEXEC

Paul Hargrove pointed out that Stevens tells us that we should
FD_GETFL before FD_SETFL.  And so we shall.

Make a new convenience function to do this (opal_fd_set_cloexec()),
just so that we don't have to litter this 2-step process throughout
the code.

Refs trac:4550

This commit was SVN r31513.

The following Trac tickets were found above:
  Ticket 4550 --> https://svn.open-mpi.org/trac/ompi/ticket/4550

opal/util/fd.c

@@ -69,3 +69,22 @@ int opal_fd_write(int fd, int len, const void *buffer)
 }
 
 
+int opal_fd_set_cloexec(int fd)
+{
+#ifdef FD_CLOEXEC
+    int flags;
+
+    /* Stevens says that we should get the fd's flags before we set
+       them.  So say we all. */
+    flags = fcntl(sd, F_GETFD, 0);
+    if (-1 == flags) {
+        return OPAL_ERR_IN_ERRNO;
+    }
+
+    if (fcntl(sd, F_SETFD, FD_CLOEXEC | flags) == -1) {
+        return OPAL_ERR_IN_ERRNO;
+    }
+#endif
+
+    return OPAL_SUCCESS;
+}

opal/util/fd.h

@@ -49,6 +49,20 @@ OPAL_DECLSPEC int opal_fd_read(int fd, int len, void *buffer);
  */
 OPAL_DECLSPEC int opal_fd_write(int fd, int len, const void *buffer);
 
+/**
+ * Convenience function to set a file descriptor to be close-on-exec.
+ *
+ * @param fd File descriptor
+ *
+ * @returns OPAL_SUCCESS upon success (or if the system does not
+ * support close-on-exec behavior).
+ * @returns OPAL_ERR_IN_ERRNO otherwise.
+ *
+ * This is simply a convenience function because there's a few steps
+ * to setting a file descriptor to be close-on-exec.
+ */
+OPAL_DECLSPEC int opal_fd_set_cloexec(int fd);
+
 END_C_DECLS
 
 #endif

orte/mca/odls/default/odls_default_module.c

@@ -419,7 +419,7 @@ static int do_child(orte_app_context_t* context,
     }
     
     /* Setup the pipe to be close-on-exec */
-    fcntl(write_fd, F_SETFD, FD_CLOEXEC);
+    opal_fd_set_cloexec(write_fd);
 
     if (NULL != child) {
         /* setup stdout/stderr so that any error messages that we

orte/mca/oob/tcp/oob_tcp_listener.c

@@ -55,6 +55,7 @@
 #include "opal/util/if.h"
 #include "opal/util/net.h"
 #include "opal/util/argv.h"
+#include "opal/util/fd.h"
 #include "opal/class/opal_hash_table.h"
 #include "opal/class/opal_list.h"
 
@@ -132,8 +133,8 @@ int orte_oob_tcp_start_listening(void)
 
         /* Make sure the pipe FDs are set to close-on-exec so that
            they don't leak into children */
-        if (fcntl(mca_oob_tcp_component.stop_thread[0], F_SETFD, FD_CLOEXEC) == -1 ||
+        if (opal_fd_set_cloexec(mca_oob_tcp_component.stop_thread[0]) != OPAL_SUCCESS ||
-            fcntl(mca_oob_tcp_component.stop_thread[1], F_SETFD, FD_CLOEXEC) == -1) {
+            opal_fd_set_cloexec(mca_oob_tcp_component.stop_thread[1]) != OPAL_SUCCESS) {
             close(mca_oob_tcp_component.stop_thread[0]);
             close(mca_oob_tcp_component.stop_thread[1]);
             ORTE_ERROR_LOG(ORTE_ERR_IN_ERRNO);

orte/tools/orterun/orterun.c

@@ -69,6 +69,7 @@
 #include "opal/util/opal_environ.h"
 #include "opal/util/opal_getcwd.h"
 #include "opal/util/show_help.h"
+#include "opal/util/fd.h"
 #include "opal/sys/atomic.h"
 #if OPAL_ENABLE_FT_CR == 1
 #include "opal/runtime/opal_cr.h"
@@ -3001,7 +3002,7 @@ static void open_fifo (void)
     }
 
     /* Set this fd to be close-on-exec so that children don't see it */
-    if (fcntl(attach_fd, F_SETFD, FD_CLOEXEC) == -1) {
+    if (opal_fd_set_cloexec(attach_fd) != OPAL_SUCCESS) {
         opal_output(0, "%s unable to set debugger attach fifo to CLOEXEC",
                     ORTE_NAME_PRINT(ORTE_PROC_MY_NAME));
         close(attach_fd);