Properly terminate C string array for execve on OSX

proc/exec_darwin.c

@@ -3,7 +3,7 @@
 extern char** environ;
 
 int
-fork_exec(char *argv0, char **argv,
+fork_exec(char *argv0, char **argv, int size,
 		mach_port_name_t *task,
 		mach_port_t *port_set,
 		mach_port_t *exception_port,
@@ -12,6 +12,8 @@ fork_exec(char *argv0, char **argv,
 	int fd[2];
 	if (pipe(fd) < 0) return -1;
 
+	argv[size-1] = '\0';
+
 	kern_return_t kret;
 	pid_t pid = fork();
 	if (pid > 0) {

proc/exec_darwin.h

@@ -6,4 +6,4 @@
 #include <stdlib.h>
 
 int
-fork_exec(char *argv0, char **argv, mach_port_name_t*, mach_port_t*, mach_port_t*, mach_port_t*);
+fork_exec(char *, char **, int, mach_port_name_t*, mach_port_t*, mach_port_t*, mach_port_t*);

proc/proc_darwin.go

@@ -51,18 +51,15 @@ func Launch(cmd []string) (*Process, error) {
 
 	argv0 := C.CString(argv0Go)
 
-	argvSlice := make([]*C.char, 0, len(cmd))
+	argvSlice := make([]*C.char, 0, len(cmd)+1)
 	for _, arg := range cmd {
 		argvSlice = append(argvSlice, C.CString(arg))
 	}
 
-	var argv **C.char
-	argv = &argvSlice[0]
-
 	dbp := New(0)
 	var pid int
 	dbp.execPtraceFunc(func() {
-		ret := C.fork_exec(argv0, argv, &dbp.os.task, &dbp.os.portSet, &dbp.os.exceptionPort, &dbp.os.notificationPort)
+		ret := C.fork_exec(argv0, &argvSlice[0], C.int(len(argvSlice)), &dbp.os.task, &dbp.os.portSet, &dbp.os.exceptionPort, &dbp.os.notificationPort)
 		pid = int(ret)
 	})
 	if pid <= 0 {