Index: config/gen/platform/generic/exec.c
===================================================================
--- config/gen/platform/generic/exec.c	(版本 42982)
+++ config/gen/platform/generic/exec.c	(工作副本)
@@ -54,11 +54,11 @@
     }
     else {
         /* child */
-        char *cmd    = Parrot_str_to_cstring(interp, command);
-        int   status = execlp("sh", "sh", "-c", cmd, (void *)NULL);
+        char * const cmd    = Parrot_str_to_cstring(interp, command);
+        int          status = execlp("sh", "sh", "-c", cmd, (void *)NULL);
 
         /* if we get here, something's horribly wrong, but free anyway... */
-        mem_sys_free(cmd);
+        Parrot_str_free_cstring(cmd);
 
         if (status)
             exit(status);
@@ -96,8 +96,7 @@
     if (child) {
         /* parent */
         int status;
-        pid_t returnstat;
-        returnstat = waitpid(child, &status, 0);
+        pid_t returnstat = waitpid(child, &status, 0);
         UNUSED(returnstat);
         return status;
     }
@@ -105,19 +104,18 @@
         /* child. Be horribly profligate with memory, since we're
            about to be something else */
         int status, i;
-        char **argv;
         STRING *s;
-        char *cmd;
+        char   *cmd;
+        char  **argv = (char **)mem_sys_allocate((len+1)*sizeof (char *));
 
-        argv = (char **)mem_sys_allocate((len+1)*sizeof (char *));
         for (i = 0; i < len; ++i) {
             s = VTABLE_get_string_keyed_int(interp, cmdargs, i);
             argv[i] = Parrot_str_to_cstring(interp, s);
         }
-        cmd = argv[0];
-        argv[i] = NULL;
 
-        status = execvp(cmd, argv);
+        cmd     = argv[0];
+        argv[i] = NULL;
+        status  = execvp(cmd, argv);
         /* if we get here, something's horribly wrong... */
         if (status) {
             exit(status);
Index: src/debug.c
===================================================================
--- src/debug.c	(版本 42982)
+++ src/debug.c	(工作副本)
@@ -1274,7 +1274,7 @@
             tmp_stdin, readline,
             "S->S", prompt, & s);
         {
-        char * aux = Parrot_str_to_cstring(interpdeb, s);
+        char * const aux = Parrot_str_to_cstring(interpdeb, s);
         strcpy(c, aux);
         Parrot_str_free_cstring(aux);
         }
Index: src/dynext.c
===================================================================
--- src/dynext.c	(版本 42982)
+++ src/dynext.c	(工作副本)
@@ -233,8 +233,8 @@
 {
     ASSERT_ARGS(dlopen_string)
 
-    char *pathstr = Parrot_str_to_cstring(interp, path);
-    void *handle = Parrot_dlopen(pathstr);
+    char * const pathstr = Parrot_str_to_cstring(interp, path);
+    void *       handle  = Parrot_dlopen(pathstr);
     Parrot_str_free_cstring(pathstr);
     return handle;
 }
Index: src/interp/inter_misc.c
===================================================================
--- src/interp/inter_misc.c	(版本 42982)
+++ src/interp/inter_misc.c	(工作副本)
@@ -341,9 +341,9 @@
 
             else {
                 /* Need to strip back to what follows the final / or \. */
-                STRING *fullname   = VTABLE_get_string(interp, exe_name);
-                char   *fullname_c = Parrot_str_to_cstring(interp, fullname);
-                int     pos        = strlen(fullname_c) - 1;
+                STRING *       fullname   = VTABLE_get_string(interp, exe_name);
+                char   * const fullname_c = Parrot_str_to_cstring(interp, fullname);
+                int            pos        = strlen(fullname_c) - 1;
 
                 while (pos              >  0
                 &&     fullname_c[pos] != '/'
@@ -354,7 +354,7 @@
                     pos++;
 
                 basename = Parrot_str_new(interp, fullname_c + pos, 0);
-                mem_sys_free(fullname_c);
+                Parrot_str_free_cstring(fullname_c);
 
                 return basename;
             }
Index: src/io/unix.c
===================================================================
--- src/io/unix.c	(版本 42982)
+++ src/io/unix.c	(工作副本)
@@ -764,7 +764,7 @@
     }
 
 #  else
-    UNUSED(l);
+    UNUSED(filehandle);
     UNUSED(command);
     UNUSED(flags);
     Parrot_ex_throw_from_c_args(interp, NULL, EXCEPTION_UNIMPLEMENTED,
Index: src/pmc/os.pmc
===================================================================
--- src/pmc/os.pmc	(版本 42982)
+++ src/pmc/os.pmc	(工作副本)
@@ -476,11 +476,11 @@
 */
     METHOD readdir(STRING *path) {
 #ifndef _MSC_VER
+        char  * const cpath = Parrot_str_to_cstring(interp, path);
+        DIR           *dir  = opendir(cpath);
         struct dirent *dirent;
         PMC           *array;
-        char          *cpath = Parrot_str_to_cstring(interp, path);
         STRING        *retval;
-        DIR           *dir   = opendir(cpath);
 
         Parrot_str_free_cstring(cpath);
 
Index: src/pmc/string.pmc
===================================================================
--- src/pmc/string.pmc	(版本 42982)
+++ src/pmc/string.pmc	(工作副本)
@@ -52,6 +52,10 @@
 
     VTABLE void mark() {
         STRING *str_val;
+
+        if (!PMC_data(SELF))
+            return;
+
         GET_ATTR_str_val(INTERP, SELF, str_val);
         Parrot_gc_mark_STRING_alive(INTERP, str_val);
     }
@@ -202,8 +206,8 @@
 
         /* Only allow constant PMCs to embed constant strings */
         if (PObj_constant_TEST(SELF) && !PObj_constant_TEST(value)) {
-            char *copy = Parrot_str_to_cstring(INTERP, value);
-            value      = Parrot_str_new_init(INTERP, copy, strlen(copy),
+            char * const copy = Parrot_str_to_cstring(INTERP, value);
+            value             = Parrot_str_new_init(INTERP, copy, strlen(copy),
                 PARROT_DEFAULT_ENCODING, PARROT_DEFAULT_CHARSET,
                 PObj_constant_FLAG);
             Parrot_str_free_cstring(copy);