Fix compiler warning.

src/lj_debug.c

@@ -137,21 +137,22 @@ static BCLine debug_frameline(lua_State *L, GCfunc *fn, cTValue *nextframe)
 /* Get name of a local variable from slot number and PC. */
 static const char *debug_varname(const GCproto *pt, BCPos pc, BCReg slot)
 {
-  const uint8_t *p = proto_varinfo(pt);
+  const char *p = (const char *)proto_varinfo(pt);
   if (p) {
     BCPos lastpc = 0;
     for (;;) {
-      const char *name = (const char *)p;
-      uint32_t vn = *p++;
+      const char *name = p;
+      uint32_t vn = *(const uint8_t *)p;
       BCPos startpc, endpc;
       if (vn < VARNAME__MAX) {
 	if (vn == VARNAME_END) break;  /* End of varinfo. */
       } else {
-	while (*p++) ;  /* Skip over variable name string. */
+	do { p++; } while (*(const uint8_t *)p);  /* Skip over variable name. */
       }
-      lastpc = startpc = lastpc + lj_buf_ruleb128((const char **)&p);
+      p++;
+      lastpc = startpc = lastpc + lj_buf_ruleb128(&p);
       if (startpc > pc) break;
-      endpc = startpc + lj_buf_ruleb128((const char **)&p);
+      endpc = startpc + lj_buf_ruleb128(&p);
       if (pc < endpc && slot-- == 0) {
 	if (vn < VARNAME__MAX) {
 #define VARNAMESTR(name, str)	str "\0"