diff -r 591377a27fa3 -r da79af4baec8 ucx/cx/string.h
--- a/ucx/cx/string.h	Tue Sep 09 16:01:30 2025 +0200
+++ b/ucx/cx/string.h	Tue Sep 09 20:56:47 2025 +0200
@@ -39,6 +39,12 @@
 #include "common.h"
 #include "allocator.h"
 
+/** Expands a UCX string as printf arguments. */
+#define CX_SFMT(s) (int) (s).length, (s).ptr
+
+/** Format specifier for a UCX string */
+#define CX_PRIstr ".*s"
+
 /**
  * The maximum length of the "needle" in cx_strstr() that can use SBO.
  */
@@ -161,6 +167,8 @@
  *
  * The length is implicitly inferred by using a call to @c strlen().
  *
+ * When @c NULL is passed, the length will be set to zero.
+ *
  * @note the wrapped string will share the specified pointer to the string.
  * If you do want a copy, use cx_strdup() on the return value of this function.
  *
@@ -171,7 +179,6 @@
  *
  * @see cx_mutstrn()
  */
-cx_attr_nonnull
 cx_attr_nodiscard
 cx_attr_cstr_arg(1)
 cx_attr_export
@@ -206,6 +213,8 @@
  *
  * The length is implicitly inferred by using a call to @c strlen().
  *
+ * When @c NULL is passed, the length will be set to zero.
+ *
  * @note the wrapped string will share the specified pointer to the string.
  * If you do want a copy, use cx_strdup() on the return value of this function.
  *
@@ -216,7 +225,6 @@
  *
  * @see cx_strn()
  */
-cx_attr_nonnull
 cx_attr_nodiscard
 cx_attr_cstr_arg(1)
 cx_attr_export
@@ -257,6 +265,10 @@
 static inline cxstring cx_strcast(cxstring str) {
     return str;
 }
+cx_attr_nodiscard
+static inline cxstring cx_strcast(const char *str) {
+    return cx_str(str);
+}
 extern "C" {
 #else
 /**
@@ -281,6 +293,17 @@
 }
 
 /**
+ * Internal function, do not use.
+ * @param str
+ * @return
+ * @see cx_strcast()
+ */
+cx_attr_nodiscard
+static inline cxstring cx_strcast_z(const char *str) {
+    return cx_str(str);
+}
+
+/**
 * Casts a mutable string to an immutable string.
 *
 * Does nothing for already immutable strings.
@@ -294,12 +317,13 @@
 */
 #define cx_strcast(str) _Generic((str), \
         cxmutstr: cx_strcast_m, \
-        cxstring: cx_strcast_c) \
-        (str)
+        cxstring: cx_strcast_c, \
+        const char*: cx_strcast_z, \
+        char *: cx_strcast_z) (str)
 #endif
 
 /**
- * Passes the pointer in this string to @c free().
+ * Passes the pointer in this string to the cxDefaultAllocator's @c free() function.
  *
  * The pointer in the struct is set to @c NULL and the length is set to zero
  * which means that this function protects you against double-free.
@@ -334,6 +358,46 @@
 );
 
 /**
+ * Copies a string.
+ *
+ * The memory in the @p dest structure is either allocated or re-allocated to fit the entire
+ * source string, including a zero-terminator.
+ *
+ * The string in @p dest is guaranteed to be zero-terminated, regardless of whether @p src is.
+ *
+ * @param alloc the allocator
+ * @param dest a pointer to the structure where to copy the contents to
+ * @param src the source string
+ *
+ * @retval zero success
+ * @retval non-zero if re-allocation failed
+ */
+cx_attr_nonnull_arg(1)
+cx_attr_export
+int cx_strcpy_a(
+        const CxAllocator *alloc,
+        cxmutstr *dest,
+        cxstring src
+);
+
+
+/**
+ * Copies a string.
+ *
+ * The memory in the @p dest structure is either allocated or re-allocated to fit the entire
+ * source string, including a zero-terminator.
+ *
+ * The string in @p dest is guaranteed to be zero-terminated, regardless of whether @p src is.
+ *
+ * @param dest (@c cxmutstr*) a pointer to the structure where to copy the contents to
+ * @param src (@c cxstring) the source string
+ *
+ * @retval zero success
+ * @retval non-zero if re-allocation failed
+ */
+#define cx_strcpy(dest, src) cx_strcpy_a(cxDefaultAllocator, dest, src)
+
+/**
  * Returns the accumulated length of all specified strings.
  * 
  * If this sum overflows, errno is set to EOVERFLOW.
@@ -408,7 +472,7 @@
 /**
  * Concatenates strings and returns a new string.
  *
- * The resulting string will be allocated by standard @c malloc().
+ * The resulting string will be allocated by the cxDefaultAllocator.
  * So developers @em must pass the return value to cx_strfree() eventually.
  *
 * If memory allocation fails, the pointer in the returned string will
@@ -428,7 +492,7 @@
 /**
  * Concatenates strings.
  *
- * The resulting string will be allocated by standard @c malloc().
+ * The resulting string will be allocated by the cxDefaultAllocator.
  * So developers @em must pass the return value to cx_strfree() eventually.
  *
  * If @p str already contains a string, the memory will be reallocated and
@@ -884,8 +948,8 @@
 /**
  * Creates a duplicate of the specified string.
  *
- * The new string will contain a copy allocated by standard
- * @c malloc(). So developers @em must pass the return value to cx_strfree().
+ * The new string will contain a copy allocated by the cxDefaultAllocator.
+ * So developers @em must pass the return value to cx_strfree().
  *
  * @note The returned string is guaranteed to be zero-terminated.
  *
@@ -1016,7 +1080,7 @@
  *
  * Replaces at most @p replmax occurrences.
  *
- * The returned string will be allocated by @c malloc() and is guaranteed
+ * The returned string will be allocated by the cxDefaultAllocator and is guaranteed
  * to be zero-terminated.
  *
  * If allocation fails, or the input string is empty,
@@ -1052,7 +1116,7 @@
 /**
  * Replaces a string with another string.
  *
- * The returned string will be allocated by @c malloc() and is guaranteed
+ * The returned string will be allocated by the cxDefaultAllocator and is guaranteed
  * to be zero-terminated.
  *
  * If allocation fails, or the input string is empty,