Check memory errors using address sanitizer

.github/release_checklist.md

@@ -5,6 +5,7 @@ Release checklist
   - [ ] Set version to a stable number.
   - [ ] Change current development version in `CHANGELOG.rst` to stable version.
   - [ ] Change the version in `__init__.py`
+- [ ] Check if the address sanitizer does not find any problems using `tox -e asan`
 - [ ] Merge the release branch into `main`.
 - [ ] Created an annotated tag with the stable version number. Include changes 
 from CHANGELOG.rst.

CHANGELOG.rst

@@ -7,6 +7,13 @@ Changelog
 .. This document is user facing. Please word the changes in such a way
 .. that users understand how the changes affect the new version.
 
+version 1.6.0-dev
+-----------------
++ Fix a memory leak that occurred when an error was thrown for a gzip header
+  with the wrong magic numbers.
++ Fix a memory leak that occurred when isal_zlib.decompressobj was given a
+  wrong wbits value.
+
 version 1.5.1
 -----------------
 + Fix a memory leak in the GzipReader.readall implementation.

src/isal/isal_zlibmodule.c

@@ -793,6 +793,7 @@ isal_zlib_decompressobj_impl(PyObject *module, int wbits, PyObject *zdict)
     err = wbits_to_flag_and_hist_bits_inflate(wbits, &hist_bits, &flag);
     if (err < 0) {
         PyErr_Format(PyExc_ValueError, "Invalid wbits value: %d", wbits);
+        Py_DECREF(self);
         return NULL;
     }
     else if (err == 0) {
@@ -1683,9 +1684,11 @@ GzipReader_read_into_buffer(GzipReader *self, uint8_t *out_buffer, size_t out_bu
 
                     if (!(magic1 == 0x1f && magic2 == 0x8b)) {
                         Py_BLOCK_THREADS;
+                        PyObject *magic_obj = PyBytes_FromStringAndSize((char *)current_pos, 2);
                         PyErr_Format(BadGzipFile,
                             "Not a gzipped file (%R)", 
-                            PyBytes_FromStringAndSize((char *)current_pos, 2));
+                            magic_obj);
+                        Py_DECREF(magic_obj);
                         return -1;
                     };
                     uint8_t method = current_pos[2];

tox.ini

@@ -22,6 +22,15 @@ commands =
     coverage html -i
     coverage xml -i
 
+[testenv:asan]
+setenv=
+    PYTHONDEVMODE=1
+    PYTHONMALLOC=malloc
+    CFLAGS=-lasan -fsanitize=address -fno-omit-frame-pointer
+allowlist_externals=bash
+commands=
+    bash -c 'export LD_PRELOAD=$(gcc -print-file-name=libasan.so) && printenv LD_PRELOAD && python -c "from isal import isal_zlib" && pytest tests'
+
 [testenv:compliance]
 deps=pytest
 commands=