From: PatR <rankin@nethack.org>
Date: Wed, 22 Sep 2021 14:59:36 +0000 (-0700)
Subject: silence compiler warning in droppables()
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=7a7550f5383c7f78a2b4bbcd7bb7eeb61e187fcd;p=nethack

silence compiler warning in droppables()

Reported by entrez as a github issue for evilhack, 'gcc -2' issued
warnings about droppables() possibly returning the address of a local
variable (&dummy).  It is mistaken; that never gets returned because
of various checks being performed.  But making 'dummy' be static adds
negligible cost and should shut it up (not verified but no doubt
about viability...).
---

diff --git a/src/dogmove.c b/src/dogmove.c
index cbb82c306..16c0b9d12 100644
--- a/src/dogmove.c
+++ b/src/dogmove.c
@@ -23,7 +23,19 @@ static void quickmimic(struct monst *);
 struct obj *
 droppables(struct monst *mon)
 {
-    struct obj *obj, *wep, dummy, *pickaxe, *unihorn, *key;
+    /*
+     * 'key|pickaxe|&c = &dummy' is used to make various creatures
+     * that can't use a key/pick-axe/&c behave as if they are already
+     * holding one so that any other such item in their inventory will
+     * be considered a duplicate and get treated as a normal candidate
+     * for dropping.
+     *
+     * This could be 'auto', but then 'gcc -O2' warns that this function
+     * might return the address of a local variable.  It's mistaken,
+     * &dummy is never returned.  'static' is simplest way to shut it up.
+     */
+    static struct obj dummy;
+    struct obj *obj, *wep, *pickaxe, *unihorn, *key;
 
     dummy = cg.zeroobj;
     dummy.otyp = GOLD_PIECE; /* not STRANGE_OBJECT or tools of interest */