[3.15] gh-151126: Set MemoryError on allocation failure in CJK codec macros (GH-156292) (#160674)

(cherry picked from commit d441a11)

Co-authored-by: Thomas Kowalski <thom.kowa@gmail.com>
Co-authored-by: Stan Ulbrych <stan@python.org>

Author: 3 people

Misc/NEWS.d/next/Library/2026-08-23-16-33-00.gh-issue-151126.GUvtG7.rst

@@ -0,0 +1,2 @@
+Fix a crash caused by failing to set :exc:`MemoryError` on allocation
+failure when first using a Chinese, Japanese or Korean codec.

Modules/cjkcodecs/cjkcodecs.h

@@ -237,6 +237,7 @@ add_mappings(cjkcodecs_module_state *st)                            \
     st->num_mappings = NUM;                                         \
     st->mapping_list = PyMem_Calloc(NUM, sizeof(struct dbcs_map));  \
     if (st->mapping_list == NULL) {                                 \
+        PyErr_NoMemory();                                           \
         return -1;                                                  \
     }
 
@@ -261,6 +262,7 @@ add_codecs(cjkcodecs_module_state *st)                          \
     st->num_codecs = NUM;                                       \
     st->codec_list = PyMem_Calloc(NUM, sizeof(MultibyteCodec)); \
     if (st->codec_list == NULL) {                               \
+        PyErr_NoMemory();                                       \
         return -1;                                              \
     }