From 10816eb91b413db99f1c3d38acf36f433c3eb49d Mon Sep 17 00:00:00 2001
From: Jouke Witteveen <j.witteveen@gmail.com>
Date: Tue, 11 Oct 2016 16:12:13 +0200
Subject: [PATCH] Do not clobber call-by-reference variables on failure

Only touch *ndevices once we are sure to not return NULL.
---
 src/XListDev.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/src/XListDev.c b/src/XListDev.c
index f850cd0..b3870e8 100644
--- a/src/XListDev.c
+++ b/src/XListDev.c
@@ -184,7 +184,7 @@ XListInputDevices(
     XAnyClassPtr Any;
     char *end = NULL;
     unsigned char *nptr, *Nptr;
-    int i;
+    int i, ndev;
     unsigned long rlen;
     XExtDisplayInfo *info = XInput_find_display(dpy);
 
@@ -202,8 +202,8 @@ XListInputDevices(
 	return (XDeviceInfo *) NULL;
     }
 
-    if ((*ndevices = rep.ndevices)) {	/* at least 1 input device */
-	size = *ndevices * sizeof(XDeviceInfo);
+    if ((ndev = rep.ndevices)) {	/* at least 1 input device */
+	size = ndev * sizeof(XDeviceInfo);
 	if (rep.length < (INT_MAX >> 2)) {
 	    rlen = rep.length << 2;	/* multiply length by 4    */
 	    slist = list = Xmalloc(rlen);
@@ -216,10 +216,10 @@ XListInputDevices(
 	}
 	_XRead(dpy, (char *)list, rlen);
 
-	any = (xAnyClassPtr) ((char *)list + (*ndevices * sizeof(xDeviceInfo)));
+	any = (xAnyClassPtr) ((char *)list + (ndev * sizeof(xDeviceInfo)));
 	sav_any = any;
 	end = (char *)list + rlen;
-	for (i = 0; i < *ndevices; i++, list++) {
+	for (i = 0; i < ndev; i++, list++) {
             s = SizeClassInfo(&any, end - (char *)any, (int)list->num_classes);
             if (!s)
                 goto out;
@@ -227,7 +227,7 @@ XListInputDevices(
 	}
 
 	Nptr = ((unsigned char *)list) + rlen;
-	for (i = 0, nptr = (unsigned char *)any; i < *ndevices; i++) {
+	for (i = 0, nptr = (unsigned char *)any; i < ndev; i++) {
 	    if (nptr >= Nptr)
 		goto out;
 	    size += *nptr + 1;
@@ -242,11 +242,12 @@ XListInputDevices(
 	    return (XDeviceInfo *) NULL;
 	}
 	sclist = clist;
+	*ndevices = ndev;
 	Any = (XAnyClassPtr) ((char *)clist +
-			      (*ndevices * sizeof(XDeviceInfo)));
+			      (ndev * sizeof(XDeviceInfo)));
 	list = slist;
 	any = sav_any;
-	for (i = 0; i < *ndevices; i++, list++, clist++) {
+	for (i = 0; i < ndev; i++, list++, clist++) {
 	    clist->type = list->type;
 	    clist->id = list->id;
 	    clist->use = list->use;
@@ -259,7 +260,7 @@ XListInputDevices(
 	clist = sclist;
 	nptr = (unsigned char *)any;
 	Nptr = (unsigned char *)Any;
-	for (i = 0; i < *ndevices; i++, clist++) {
+	for (i = 0; i < ndev; i++, clist++) {
 	    clist->name = (char *)Nptr;
 	    memcpy(Nptr, nptr + 1, *nptr);
 	    Nptr += (*nptr);
-- 
2.10.0