From e0cbaa50fa7e97a8b7404041a59caac47b3949a5 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Tue, 17 Dec 2019 10:49:55 -0300
Subject: [PATCH] Added test for NULL in string.format("%p")

ISO C states that standard library functions should not be called
with NULL arguments, unless stated otherwise. 'sprintf' does not
state otherwise, and it doesn't hurt to be on the safe side.
---
 lstrlib.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lstrlib.c b/lstrlib.c
index 586e0d78..e47a1d8d 100644
--- a/lstrlib.c
+++ b/lstrlib.c
@@ -1271,6 +1271,8 @@ static int str_format (lua_State *L) {
         }
         case 'p': {
           const void *p = lua_topointer(L, arg);
+          if (p == NULL)
+            p = "(null)";  /* NULL not a valid parameter in ISO C 'printf' */
           nb = l_sprintf(buff, maxitem, form, p);
           break;
         }