From 3f37b07864c4076c0290e20a3fa0e51788bf37cf Mon Sep 17 00:00:00 2001
From: "Enrico Weigelt, metux IT consult" <info@metux.net>
Date: Tue, 16 Jul 2024 19:43:01 +0200
Subject: [PATCH] dbe: simplify temporary buffer allocation via local stack

Small buffers easily fit on stack, so their allocation can be simplified.
No need to go through heap and have extra free() calls on each return point.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
---
 dbe/dbe.c | 54 +++++++++++++-----------------------------------------
 1 file changed, 13 insertions(+), 41 deletions(-)

diff --git a/dbe/dbe.c b/dbe/dbe.c
index b9c57b884..298639896 100644
--- a/dbe/dbe.c
+++ b/dbe/dbe.c
@@ -442,7 +442,6 @@ ProcDbeSwapBuffers(ClientPtr client)
     REQUEST(xDbeSwapBuffersReq);
     WindowPtr pWin;
     DbeScreenPrivPtr pDbeScreenPriv;
-    DbeSwapInfoPtr swapInfo;
     xDbeSwapInfo *dbeSwapInfo;
     int error;
     unsigned int i, j;
@@ -465,10 +464,7 @@ ProcDbeSwapBuffers(ClientPtr client)
     dbeSwapInfo = (xDbeSwapInfo *) &stuff[1];
 
     /* Allocate array to record swap information. */
-    swapInfo = xallocarray(nStuff, sizeof(DbeSwapInfoRec));
-    if (swapInfo == NULL) {
-        return BadAlloc;
-    }
+    DbeSwapInfoRec swapInfo[nStuff];
 
     for (i = 0; i < nStuff; i++) {
         /* Check all windows to swap. */
@@ -476,38 +472,29 @@ ProcDbeSwapBuffers(ClientPtr client)
         /* Each window must be a valid window - BadWindow. */
         error = dixLookupWindow(&pWin, dbeSwapInfo[i].window, client,
                                 DixWriteAccess);
-        if (error != Success) {
-            free(swapInfo);
+        if (error != Success)
             return error;
-        }
 
         /* Each window must be double-buffered - BadMatch. */
-        if (DBE_WINDOW_PRIV(pWin) == NULL) {
-            free(swapInfo);
+        if (DBE_WINDOW_PRIV(pWin) == NULL)
             return BadMatch;
-        }
 
         /* Each window must only be specified once - BadMatch. */
         for (j = i + 1; j < nStuff; j++) {
-            if (dbeSwapInfo[i].window == dbeSwapInfo[j].window) {
-                free(swapInfo);
+            if (dbeSwapInfo[i].window == dbeSwapInfo[j].window)
                 return BadMatch;
-            }
         }
 
         /* Each swap action must be valid - BadValue. */
         if ((dbeSwapInfo[i].swapAction != XdbeUndefined) &&
             (dbeSwapInfo[i].swapAction != XdbeBackground) &&
             (dbeSwapInfo[i].swapAction != XdbeUntouched) &&
-            (dbeSwapInfo[i].swapAction != XdbeCopied)) {
-            free(swapInfo);
+            (dbeSwapInfo[i].swapAction != XdbeCopied))
             return BadValue;
-        }
 
         /* Everything checks out OK.  Fill in the swap info array. */
         swapInfo[i].pWindow = pWin;
         swapInfo[i].swapAction = dbeSwapInfo[i].swapAction;
-
     }                           /* for (i = 0; i < nStuff; i++) */
 
     /* Call the DDX routine to perform the swap(s).  The DDX routine should
@@ -527,17 +514,13 @@ ProcDbeSwapBuffers(ClientPtr client)
     while (nStuff_i > 0) {
         pDbeScreenPriv = DBE_SCREEN_PRIV_FROM_WINDOW(swapInfo[0].pWindow);
         error = (*pDbeScreenPriv->SwapBuffers) (client, &nStuff_i, swapInfo);
-        if (error != Success) {
-            free(swapInfo);
+        if (error != Success)
             return error;
-        }
     }
 
-    free(swapInfo);
     return Success;
+}
 
-}                               /* ProcDbeSwapBuffers() */
-
 /******************************************************************************
  *
  * DBE DIX Procedure: ProcDbeGetVisualInfo
@@ -561,13 +544,10 @@ ProcDbeGetVisualInfo(ClientPtr client)
     REQUEST(xDbeGetVisualInfoReq);
     DbeScreenPrivPtr pDbeScreenPriv;
     xDbeGetVisualInfoReply rep;
-    Drawable *drawables;
-    DrawablePtr *pDrawables = NULL;
     register int i, j, rc;
     register int count;         /* number of visual infos in reply */
     register int length;        /* length of reply */
     ScreenPtr pScreen;
-    XdbeScreenVisualInfo *pScrVisInfo;
 
     REQUEST_AT_LEAST_SIZE(xDbeGetVisualInfoReq);
     if (stuff->n > UINT32_MAX / sizeof(CARD32))
@@ -576,30 +556,25 @@ ProcDbeGetVisualInfo(ClientPtr client)
 
     if (stuff->n > UINT32_MAX / sizeof(DrawablePtr))
         return BadAlloc;
+
+    DrawablePtr pDrawables[stuff->n * sizeof(DrawablePtr)];
+
     /* Make sure any specified drawables are valid. */
     if (stuff->n != 0) {
-        if (!(pDrawables = xallocarray(stuff->n, sizeof(DrawablePtr)))) {
-            return BadAlloc;
-        }
-
-        drawables = (Drawable *) &stuff[1];
+        Drawable *drawables = (Drawable *) &stuff[1];
 
         for (i = 0; i < stuff->n; i++) {
             rc = dixLookupDrawable(pDrawables + i, drawables[i], client, 0,
                                    DixGetAttrAccess);
             if (rc != Success) {
-                free(pDrawables);
                 return rc;
             }
         }
     }
 
     count = (stuff->n == 0) ? screenInfo.numScreens : stuff->n;
-    if (!(pScrVisInfo = calloc(count, sizeof(XdbeScreenVisualInfo)))) {
-        free(pDrawables);
-
-        return BadAlloc;
-    }
+    XdbeScreenVisualInfo pScrVisInfo[count];
+    memset(pScrVisInfo, 0, sizeof(pScrVisInfo));
 
     length = 0;
 
@@ -690,9 +665,6 @@ ProcDbeGetVisualInfo(ClientPtr client)
     for (i = 0; i < count; i++) {
         free(pScrVisInfo[i].visinfo);
     }
-    free(pScrVisInfo);
-
-    free(pDrawables);
 
     return rc;