block alloc: add validations around cache_entry lifecyle

diff --git a/read-cache.c b/read-cache.c
index b07369660baa64961c08ab7bac41e7d3f75c3710..fd67e2e8a48b4f28d923b4ba7354b02f203d8d7f 100644 (file)
--- a/read-cache.c
+++ b/read-cache.c
@@ -2050,8 +2050,10 @@ int discard_index(struct index_state *istate)
         * Cache entries in istate->cache[] should have been allocated
         * from the memory pool associated with this index, or from an
         * associated split_index. There is no need to free individual
-        * cache entries.
+        * cache entries. validate_cache_entries can detect when this
+        * assertion does not hold.
         */
+       validate_cache_entries(istate);
 
        resolve_undo_clear_index(istate);
        istate->cache_nr = 0;
@@ -2068,13 +2070,45 @@ int discard_index(struct index_state *istate)
        istate->untracked = NULL;
 
        if (istate->ce_mem_pool) {
-               mem_pool_discard(istate->ce_mem_pool);
+               mem_pool_discard(istate->ce_mem_pool, should_validate_cache_entries());
                istate->ce_mem_pool = NULL;
        }
 
        return 0;
 }
 
+/*
+ * Validate the cache entries of this index.
+ * All cache entries associated with this index
+ * should have been allocated by the memory pool
+ * associated with this index, or by a referenced
+ * split index.
+ */
+void validate_cache_entries(const struct index_state *istate)
+{
+       int i;
+
+       if (!should_validate_cache_entries() ||!istate || !istate->initialized)
+               return;
+
+       for (i = 0; i < istate->cache_nr; i++) {
+               if (!istate) {
+                       die("internal error: cache entry is not allocated from expected memory pool");
+               } else if (!istate->ce_mem_pool ||
+                       !mem_pool_contains(istate->ce_mem_pool, istate->cache[i])) {
+                       if (!istate->split_index ||
+                               !istate->split_index->base ||
+                               !istate->split_index->base->ce_mem_pool ||
+                               !mem_pool_contains(istate->split_index->base->ce_mem_pool, istate->cache[i])) {
+                               die("internal error: cache entry is not allocated from expected memory pool");
+                       }
+               }
+       }
+
+       if (istate->split_index)
+               validate_cache_entries(istate->split_index->base);
+}
+
 int unmerged_index(const struct index_state *istate)
 {
        int i;
@@ -2878,8 +2912,25 @@ struct cache_entry *dup_cache_entry(const struct cache_entry *ce,
 
 void discard_cache_entry(struct cache_entry *ce)
 {
+       if (ce && should_validate_cache_entries())
+               memset(ce, 0xCD, cache_entry_size(ce->ce_namelen));
+
        if (ce && ce->mem_pool_allocated)
                return;
 
        free(ce);
 }
+
+int should_validate_cache_entries(void)
+{
+       static int validate_index_cache_entries = -1;
+
+       if (validate_index_cache_entries < 0) {
+               if (getenv("GIT_TEST_VALIDATE_INDEX_CACHE_ENTRIES"))
+                       validate_index_cache_entries = 1;
+               else
+                       validate_index_cache_entries = 0;
+       }
+
+       return validate_index_cache_entries;
+}