shithub: libvpx

Download patch

ref: 34e191b2f16a7375c1e19d50f91467dffe2f0bc3
parent: ecc31d28781c490f5fb18a3e6873692a1b8e6cea
author: Wan-Teh Chang <wtc@google.com>
date: Mon Oct 8 05:41:55 EDT 2018 

Avoid null checks related to pool->frame_bufs.

It seems that null pointer checks such as the following may make clang
scan-build think pool->frame_bufs may be a null pointer:

    buf = (buf_idx != INVALID_IDX) ? &pool->frame_bufs[buf_idx] : NULL;
    if (buf != NULL) {

This "misinformation" may make scan-build warn about the ref_cnt_fb()
function's use of its 'bufs' argument (Dereference of null pointer) when
we pass pool->frame_bufs to ref_cnt_fb().

Rewriting the above code as:

    if (buf_idx != INVALID_IDX) {
      buf = &pool->frame_bufs[buf_idx];

not only is clearer but also avoids confusing scan-build.

Change-Id: Ia64858dbd7ff89f74ba1a4fc9239b0c4413592c8


--- a/vp9/encoder/vp9_encoder.c
+++ b/vp9/encoder/vp9_encoder.c
@@ -3217,8 +3217,8 @@
         if (cpi->oxcf.pass == 0 && !cpi->use_svc) {
           // Check for release of scaled reference.
           buf_idx = cpi->scaled_ref_idx[ref_frame - 1];
-          buf = (buf_idx != INVALID_IDX) ? &pool->frame_bufs[buf_idx] : NULL;
-          if (buf != NULL) {
+          if (buf_idx != INVALID_IDX) {
+            buf = &pool->frame_bufs[buf_idx];
             --buf->ref_count;
             cpi->scaled_ref_idx[ref_frame - 1] = INVALID_IDX;
           }
@@ -3249,22 +3249,21 @@
     refresh[2] = (cpi->refresh_alt_ref_frame) ? 1 : 0;
     for (i = LAST_FRAME; i <= ALTREF_FRAME; ++i) {
       const int idx = cpi->scaled_ref_idx[i - 1];
-      RefCntBuffer *const buf =
-          idx != INVALID_IDX ? &cm->buffer_pool->frame_bufs[idx] : NULL;
-      const YV12_BUFFER_CONFIG *const ref = get_ref_frame_buffer(cpi, i);
-      if (buf != NULL &&
-          (refresh[i - 1] || (buf->buf.y_crop_width == ref->y_crop_width &&
-                              buf->buf.y_crop_height == ref->y_crop_height))) {
-        --buf->ref_count;
-        cpi->scaled_ref_idx[i - 1] = INVALID_IDX;
+      if (idx != INVALID_IDX) {
+        RefCntBuffer *const buf = &cm->buffer_pool->frame_bufs[idx];
+        const YV12_BUFFER_CONFIG *const ref = get_ref_frame_buffer(cpi, i);
+        if (refresh[i - 1] || (buf->buf.y_crop_width == ref->y_crop_width &&
+                               buf->buf.y_crop_height == ref->y_crop_height)) {
+          --buf->ref_count;
+          cpi->scaled_ref_idx[i - 1] = INVALID_IDX;
+        }
       }
     }
   } else {
     for (i = 0; i < MAX_REF_FRAMES; ++i) {
       const int idx = cpi->scaled_ref_idx[i];
-      RefCntBuffer *const buf =
-          idx != INVALID_IDX ? &cm->buffer_pool->frame_bufs[idx] : NULL;
-      if (buf != NULL) {
+      if (idx != INVALID_IDX) {
+        RefCntBuffer *const buf = &cm->buffer_pool->frame_bufs[idx];
         --buf->ref_count;
         cpi->scaled_ref_idx[i] = INVALID_IDX;
       }