dix: ProcListProperties: skip unneeded work if numProps is 0

No real harm, but clears warning from gcc 14.1:

../dix/property.c: In function ‘ProcListProperties’:
..//dix/property.c:605:27: warning: dereference of NULL ‘temppAtoms’
 [CWE-476] [-Wanalyzer-null-dereference]
  605 |             *temppAtoms++ = pProp->propertyName;
      |             ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1673>

1 files changed, 15 insertions, 12 deletions

diff --git a/dix/property.c b/dix/property.c
index b51b371f0..501c54698 100644
--- a/dix/property.c
+++ b/dix/property.c
@@ -593,17 +593,20 @@ ProcListProperties(ClientPtr client)
     for (pProp = wUserProps(pWin); pProp; pProp = pProp->next)
         numProps++;
 
-    if (numProps && !(pAtoms = xallocarray(numProps, sizeof(Atom))))
-        return BadAlloc;
-
-    numProps = 0;
-    temppAtoms = pAtoms;
-    for (pProp = wUserProps(pWin); pProp; pProp = pProp->next) {
-        realProp = pProp;
-        rc = XaceHookPropertyAccess(client, pWin, &realProp, DixGetAttrAccess);
-        if (rc == Success && realProp == pProp) {
-            *temppAtoms++ = pProp->propertyName;
-            numProps++;
+    if (numProps) {
+        pAtoms = xallocarray(numProps, sizeof(Atom));
+        if (!pAtoms)
+            return BadAlloc;
+
+        numProps = 0;
+        temppAtoms = pAtoms;
+        for (pProp = wUserProps(pWin); pProp; pProp = pProp->next) {
+            realProp = pProp;
+            rc = XaceHookPropertyAccess(client, pWin, &realProp, DixGetAttrAccess);
+            if (rc == Success && realProp == pProp) {
+                *temppAtoms++ = pProp->propertyName;
+                numProps++;
+            }
         }
     }
 
@@ -617,8 +620,8 @@ ProcListProperties(ClientPtr client)
     if (numProps) {
         client->pSwapReplyFunc = (ReplySwapPtr) Swap32Write;
         WriteSwappedDataToClient(client, numProps * sizeof(Atom), pAtoms);
+        free(pAtoms);
     }
-    free(pAtoms);
     return Success;
 }