c-stdaux: re-import git-subtree for 'src/c-stdaux'

git subtree pull --prefix src/c-stdaux git@github.com:c-util/c-stdaux.git main --squash

src/c-stdaux/.github/workflows/ci.yml

@@ -25,6 +25,6 @@ jobs:
       macos: true
   ci-docs:
     name: Documentation CI
-    uses: bus1/cabuild/.github/workflows/ci-sphinx.yml@main
+    uses: bus1/cabuild/.github/workflows/ci-sphinx.yml@v1
     with:
       source: "./src/docs"

src/c-stdaux/README.md

@@ -11,6 +11,7 @@ common extended features of wide-spread compilers like gcc and clang.
 ### Project
 
  * **Website**: <https://c-util.github.io/c-stdaux>
+ * **Documentation**: <https://c-stdaux.readthedocs.io>
  * **Bug Tracker**: <https://github.com/c-util/c-stdaux/issues>
 
 ### Requirements

src/c-stdaux/src/c-stdaux.h

@@ -677,6 +677,23 @@ static inline void *c_memcpy(void *dst, const void *src, size_t n) {
         return dst;
 }
 
+/**
+ * c_memcmp() - Compare memory areas
+ * @s1:         Pointer to one area
+ * @s2:         Pointer to other area
+ * @n:          Length of area to compare
+ *
+ * Compare the memory of size ``n`` of ``s1`` and ``s2``, just as ``memcmp(3)``
+ * does, except this function allows either to be ``NULL`` if ``n`` is zero.
+ *
+ * Return: Comparison result for ordering is returned.
+ */
+static inline int c_memcmp(const void *s1, const void *s2, size_t n) {
+        if (n > 0)
+                return memcmp(s1, s2, n);
+        return 0;
+}
+
 /**
  * DOC: Common Destructors
  *

src/c-stdaux/src/test-basic.c

@@ -357,6 +357,17 @@ static void test_misc(int non_constant_expr) {
 
                 c_memcpy(NULL, NULL, 0);
         }
+
+        /*
+         * Test c_memcmp() with.
+         */
+        {
+                uint64_t v1 = (uint64_t)-1, v2 = (uint64_t)0;
+
+                c_assert(c_memcmp(NULL, NULL, 0) == 0);
+                c_assert(c_memcmp(&v1, &v2, 0) == 0);
+                c_assert(c_memcmp(&v1, &v2, 8) != 0);
+        }
 }
 
 /*