don't use str{cpy,cat} in mruby and mrbc

The length of each string is known. It should be used.

mrbgems/mruby-bin-mruby/tools/mruby/mruby.c

@@ -91,16 +91,24 @@ parse_args(mrb_state *mrb, int argc, char **argv, struct _args *args)
         item = argv[0];
 append_cmdline:
         if (!args->cmdline) {
+          size_t buflen;
           char *buf;
 
-          buf = (char *)mrb_malloc(mrb, strlen(item)+1);
-          strcpy(buf, item);
+          buflen = strlen(item) + 1;
+          buf = (char *)mrb_malloc(mrb, buflen);
+          memcpy(buf, item, buflen);
           args->cmdline = buf;
         }
         else {
-          args->cmdline = (char *)mrb_realloc(mrb, args->cmdline, strlen(args->cmdline)+strlen(item)+2);
-          strcat(args->cmdline, "\n");
-          strcat(args->cmdline, item);
+          size_t cmdlinelen;
+          size_t itemlen;
+
+          cmdlinelen = strlen(args->cmdline);
+          itemlen = strlen(item);
+          args->cmdline =
+            (char *)mrb_realloc(mrb, args->cmdline, cmdlinelen + itemlen + 2);
+          args->cmdline[cmdlinelen] = '\n';
+          memcpy(args->cmdline + cmdlinelen + 1, item, itemlen + 1);
         }
       }
       else {

tools/mrbc/mrbc.c

@@ -51,15 +51,19 @@ usage(const char *name)
 static char *
 get_outfilename(mrb_state *mrb, char *infile, char *ext)
 {
+  size_t infilelen;
+  size_t extlen;
   char *outfile;
   char *p;
 
-  outfile = (char*)mrb_malloc(mrb, strlen(infile) + strlen(ext) + 1);
-  strcpy(outfile, infile);
+  infilelen = strlen(infile);
+  extlen = strlen(ext);
+  outfile = (char*)mrb_malloc(mrb, infilelen + extlen + 1);
+  memcpy(outfile, infile, infilelen + 1);
   if (*ext) {
     if ((p = strrchr(outfile, '.')) == NULL)
-      p = &outfile[strlen(outfile)];
-    strcpy(p, ext);
+      p = outfile + infilelen;
+    memcpy(p, ext, extlen + 1);
   }
 
   return outfile;