ticket [c54e4a1aeb] patch: Use vfork instead fork.

1 files changed, 47 insertions, 3 deletions

diff --git a/unix/tclUnixPipe.c b/unix/tclUnixPipe.c
index 75e2879..9b66083 100644
--- a/unix/tclUnixPipe.c
+++ b/unix/tclUnixPipe.c
@@ -13,6 +13,12 @@
 
 #include "tclInt.h"
 
+#define USE_POSIX_SPAWN 1
+
+#ifdef USE_POSIX_SPAWN
+# include <spawn.h>
+#endif
+
 #ifdef USE_VFORK
 #define fork vfork
 #endif
@@ -439,7 +445,7 @@ TclpCreateProcess(
 	newArgv[i] = Tcl_UtfToExternalDString(NULL, argv[i], -1, &dsArray[i]);
     }
 
-#ifdef USE_VFORK
+#if defined(USE_VFORK) || defined(USE_POSIX_SPAWN)
     /*
      * After vfork(), do not call code in the child that changes global state,
      * because it is using the parent's memory space at that point and writes
@@ -452,14 +458,52 @@ TclpCreateProcess(
 	Tcl_GetStdChannel(TCL_STDIN);
     }
     if (!outputFile) {
-        Tcl_GetStdChannel(TCL_STDOUT);
+	Tcl_GetStdChannel(TCL_STDOUT);
     }
     if (!errorFile) {
-        Tcl_GetStdChannel(TCL_STDERR);
+	Tcl_GetStdChannel(TCL_STDERR);
     }
 #endif
 
+#ifdef USE_POSIX_SPAWN
+    {
+	posix_spawn_file_actions_t actions;
+	posix_spawnattr_t attr;
+
+	posix_spawn_file_actions_init(&actions);
+	posix_spawnattr_init(&attr);
+
+	posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGDEF|
+# ifdef POSIX_SPAWN_USEVFORK
+		POSIX_SPAWN_USEVFORK
+# else
+		0
+# endif
+		);
+	posix_spawn_file_actions_adddup2(&actions, GetFd(inputFile), 0);
+	posix_spawn_file_actions_adddup2(&actions, GetFd(outputFile), 1);
+	posix_spawn_file_actions_adddup2(&actions, GetFd(errorFile), 2);
+
+	status = posix_spawnp(&pid, newArgv[0], &actions, &attr, newArgv, environ);
+
+	posix_spawn_file_actions_destroy(&actions);
+	posix_spawnattr_destroy(&attr);
+
+	/*
+	 * Fork semantics:
+	 *  - pid == 0: child process
+	 *  - pid == -1: error
+	 *  - pid > 0: parent process
+	 *
+	 * Mimic fork semantics to minimize changes below
+	 */
+	if (status != 0) {
+	    pid = -1;
+	}
+    }
+#else  
     pid = fork();
+#endif
     if (pid == 0) {
 	size_t len;
 	int joinThisError = errorFile && (errorFile == outputFile);