ImBuf: Add error handling to IMB_indexer_open

Handle return value of `fread()` by printing an error and closing the
file when it cannot be read from. Not only is error handing a good idea,
it also prevents GCC from warning that the return value of `fread()`
should not be ignored:

```
.../blender/source/blender/imbuf/intern/indexer.c: In function ‘IMB_indexer_open’:
.../blender/source/blender/imbuf/intern/indexer.c:201:5: warning: ignoring return value of ‘fread’, declared with attribute warn_unused_result [-Wunused-result]
  201 |     fread(&idx->entries[i].frameno, sizeof(int), 1, fp);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.../blender/source/blender/imbuf/intern/indexer.c:202:5: warning: ignoring return value of ‘fread’, declared with attribute warn_unused_result [-Wunused-result]
  202 |     fread(&idx->entries[i].seek_pos, sizeof(unsigned long long), 1, fp);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.../blender/source/blender/imbuf/intern/indexer.c:203:5: warning: ignoring return value of ‘fread’, declared with attribute warn_unused_result [-Wunused-result]
  203 |     fread(&idx->entries[i].seek_pos_dts, sizeof(unsigned long long), 1, fp);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.../blender/source/blender/imbuf/intern/indexer.c:204:5: warning: ignoring return value of ‘fread’, declared with attribute warn_unused_result [-Wunused-result]
  204 |     fread(&idx->entries[i].pts, sizeof(unsigned long long), 1, fp);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

Differential Revision: https://developer.blender.org/D9916

Reviewed by: campbellbarton

1 files changed, 13 insertions, 4 deletions

diff --git a/source/blender/imbuf/intern/indexer.c b/source/blender/imbuf/intern/indexer.c
index b5b8cd4a580..09f37d733de 100644
--- a/source/blender/imbuf/intern/indexer.c
+++ b/source/blender/imbuf/intern/indexer.c
@@ -198,10 +198,19 @@ struct anim_index *IMB_indexer_open(const char *name)
                              "anim_index_entries");
 
   for (i = 0; i < idx->num_entries; i++) {
-    fread(&idx->entries[i].frameno, sizeof(int), 1, fp);
-    fread(&idx->entries[i].seek_pos, sizeof(unsigned long long), 1, fp);
-    fread(&idx->entries[i].seek_pos_dts, sizeof(unsigned long long), 1, fp);
-    fread(&idx->entries[i].pts, sizeof(unsigned long long), 1, fp);
+    size_t items_read = 0;
+    items_read += fread(&idx->entries[i].frameno, sizeof(int), 1, fp);
+    items_read += fread(&idx->entries[i].seek_pos, sizeof(unsigned long long), 1, fp);
+    items_read += fread(&idx->entries[i].seek_pos_dts, sizeof(unsigned long long), 1, fp);
+    items_read += fread(&idx->entries[i].pts, sizeof(unsigned long long), 1, fp);
+
+    if (items_read < 4) {
+      perror("error reading animation index file");
+      MEM_freeN(idx->entries);
+      MEM_freeN(idx);
+      fclose(fp);
+      return NULL;
+    }
   }
 
   if (((ENDIAN_ORDER == B_ENDIAN) != (header[8] == 'V'))) {