iemejia opened a new pull request, #3969:
URL: https://github.com/apache/avro/pull/3969

   ## What changes were proposed in this pull request?
   
   The vendored `st` hash table used by the C SDK (`lang/c/src/st.c`) allocated 
table entries via `avro_new()` inside the `ADD_DIRECT` macro (used by 
`st_insert()` and `st_add_direct()`) **without checking for a NULL return**:
   
   ```c
   entry = (st_table_entry *) avro_new(st_table_entry);
   entry->hash = hash_val;   /* NULL-dereference on allocation failure */
   ```
   
   On allocation failure this dereferenced NULL and crashed rather than 
reporting an error, so map decoding — and every other `st` user — was not 
OOM-safe on that path. `rehash()`, which runs inside `ADD_DIRECT`, had the same 
problem with the `Calloc()` of its new bin array.
   
   Noted during review of AVRO-4293 (bounded allocation when decoding 
length-prefixed values/collections); that PR fixed the `map.c` side but 
deliberately left this shared-code change out of scope.
   
   ## How was this patch fixed?
   
   - `ADD_DIRECT` now receives a **pre-allocated** entry. `st_insert()` 
allocates it, returns `-1` on failure and leaves the table unchanged (`0` = 
inserted, `1` = updated, as before). `st_add_direct()` (which returns `void`) 
becomes a no-op on allocation failure instead of crashing.
   - `rehash()` skips the rehash and keeps the existing bins when the new bin 
array cannot be allocated — the table stays correct, only denser.
   - The only caller that inspects the return value (`save_named_schemas` in 
`schema.c`) already treats any non-zero as an error, so the new `-1` propagates 
correctly. All other callers ignore the return value and simply observe an 
unchanged table.
   
   `st_insert`'s contract is documented in `st.h`.
   
   ## How was this patch tested?
   
   New `test_avro_4305` installs a failing allocator and verifies that:
   - `st_insert()` returns `-1` on OOM **without crashing** and leaves the 
table unchanged;
   - a subsequent insert (memory available again) still succeeds and is 
retrievable.
   
   Verified the test **segfaults without the fix** (SIGSEGV) and passes with 
it. Full C suite: **54/54** tests pass, including the valgrind 
`memcheck_test_avro_4305` variant (no leaks).


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