feat(string): complete string.h + strdup/memccpy

src/string/strcpy.c

@@ -0,0 +1,31 @@
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <string.h>
+
+/*
+ * Copy src to dst including the terminating NUL; return dst. The strings
+ * must not overlap (restrict).
+ *
+ * The copy loop below is the canonical strcpy idiom; GCC's
+ * -ftree-loop-distribute-patterns (on by default at -O2 and -O3) can rewrite
+ * such loops into calls to the recognized string builtins — potentially this
+ * very function — causing infinite self-recursion. Disable that one
+ * transformation for this function only.
+ */
+__attribute__((optimize("no-tree-loop-distribute-patterns"))) char *
+strcpy(char *restrict dst, const char *restrict src) // NOLINT(bugprone-*)
+{
+    char *d = dst;
+
+    for (;;)
+    {
+        *d++ = *src;
+        if (*src == '\0')
+        {
+            return dst;
+        }
+        src++;
+    }
+}