str: handle NULL input in create()

* Check for NULL in cdada_str_create()
* Add regression and CHANGELOG

Reported-by: CodexGPT-5.3 <noreply@openai.com>

Author: msune

CHANGELOG.md

@@ -15,9 +15,11 @@ Legend:
 - [B] utils: add missing human-readable message for `CDADA_E_FULL`
 - [B] list/map/queue/set/stack: return `NULL` when constructor `malloc()` fails (avoid null dereference)
 - [B] str: fix `cdada_str_replace*()` to reject empty match and self-replacement issues
+- [B] str: return `NULL` in `cdada_str_create()` when input C string is `NULL`
 - [O] tests: add coverage for `cdada_strerr()` valid, boundary and high invalid values
 - [O] tests: add `oom_create_test` coverage for create paths (`list`, `map`, `queue`, `set`, `stack`, `str`, `bbitmap`)
 - [O] tests: add coverage for `cdada_str_replace_all()` empty-match invalid input and self-overlap replacement
+- [O] tests: add `cdada_str_create(NULL)` regression coverage
 
 ### v0.6.3 (28th January 2026)
 

src/str.cc

@@ -12,6 +12,9 @@ cdada_str_t* cdada_str_create(const char* str){
 
 	__cdada_str_int_t* m = NULL;
 
+	if(!str)
+		return NULL;
+
 	m = (__cdada_str_int_t*)malloc(sizeof(__cdada_str_int_t));
 	if(!m)
 		return NULL;

test/str_test.c

@@ -114,6 +114,9 @@ int test_basics(){
 	void* ptr_not_null = (void*)0x123;
 
 	//Create
+	s = cdada_str_create(NULL);
+	TEST_ASSERT(s == NULL);
+
 	s = cdada_str_create("HELLO");
 	TEST_ASSERT(s != NULL);