allocate enough space for NUL, and do not try to open an empty file string

src/drivers/libretro/libretro.c

@@ -172,7 +172,10 @@ void FCEUD_VideoChanged (void)
 
 FILE *FCEUD_UTF8fopen(const char *n, const char *m)
 {
-   return fopen(n, m);
+   if (n)
+      return fopen(n, m);
+   else
+      return NULL;
 }
 
 #define MAX_PATH 1024

src/general.c

@@ -91,8 +91,9 @@ char *FCEU_MakeFName(int type, int id1, char *cd1)
          break;
    }
 
-   ret = (char*)malloc(strlen(tmp) * sizeof(char));
+   ret = (char*)malloc(strlen(tmp) * sizeof(char) + 1);
-   strncpy(ret, tmp, strlen(tmp));
+   strncpy(ret, tmp, strlen(tmp) + 1);
+
    return(ret);
 }
 

src/state.c

@@ -324,8 +324,14 @@ void FCEUSS_CheckStates(void)
 
    for (ssel = 0; ssel < 10; ssel++)
    {
-      st = fopen(fn = FCEU_MakeFName(FCEUMKF_STATE, ssel, 0), "rb");
+      fn = FCEU_MakeFName(FCEUMKF_STATE, ssel, 0);
-      free(fn);
+
+      if (fn)
+      {
+         st = fopen(fn, "rb");
+         free(fn);
+      }
+
       if (st)
       {
          SaveStateStatus[ssel] = 1;