diff -r e8f354a25ac8 -r 68754c7de906 src/cx/common.h
--- a/src/cx/common.h	Thu Nov 07 20:22:56 2024 +0100
+++ b/src/cx/common.h	Thu Nov 07 22:46:58 2024 +0100
@@ -88,13 +88,166 @@
 /** Version constant which ensures to increase monotonically. */
 #define UCX_VERSION (((UCX_VERSION_MAJOR)<<16)|UCX_VERSION_MINOR)
 
-// Common Includes
+// ---------------------------------------------------------------------------
+//       Common includes
+// ---------------------------------------------------------------------------
 
 #include <stdlib.h>
 #include <stddef.h>
 #include <stdbool.h>
 #include <stdint.h>
 
+// ---------------------------------------------------------------------------
+//       Attribute definitions
+// ---------------------------------------------------------------------------
+
+#ifndef __GNUC__
+/**
+ * Removes GNU C attributes where they are not supported.
+ */
+#define __attribute__(x)
+#endif
+
+/**
+ * All pointer arguments must be non-NULL.
+ */
+#define cx_attr_nonnull __attribute__((__nonnull__))
+
+/**
+ * The specified pointer arguments must be non-NULL.
+ */
+#define cx_attr_nonnull_arg(...) __attribute__((__nonnull__(__VA_ARGS__)))
+
+/**
+ * The returned value is guaranteed to be non-NULL.
+ */
+#define cx_attr_returns_nonnull __attribute__((__returns_nonnull__))
+
+/**
+ * The attributed function always returns freshly allocated memory.
+ */
+#define cx_attr_malloc __attribute__((__malloc__))
+
+#ifndef __clang__
+/**
+ * The pointer returned by the attributed function is supposed to be freed
+ * by \p freefunc.
+ *
+ * @param freefunc the function that shall be used to free the memory
+ * @param freefunc_arg the index of the pointer argument in \p freefunc
+ */
+#define cx_attr_dealloc(freefunc, freefunc_arg) \
+    __attribute__((__malloc__(freefunc, freefunc_arg)))
+#else
+/**
+ * Not supported in clang.
+ */
+#define cx_attr_dealloc(...)
+#endif // __clang__
+
+/**
+ * Shortcut to specify #cxFree() as deallocator.
+ */
+#define cx_attr_dealloc_ucx cx_attr_dealloc(cxFree, 2)
+
+/**
+ * Specifies the parameters from which the allocation size is calculated.
+ */
+#define cx_attr_allocsize(...) __attribute__((__alloc_size__(__VA_ARGS__)))
+
+
+#ifdef __clang__
+/**
+ * No support for \c null_terminated_string_arg in clang or GCC below 14.
+ */
+#define cx_attr_cstr_arg(idx)
+/**
+ * No support for access attribute in clang.
+ */
+#define cx_attr_access(mode, ...)
+#else
+#if __GNUC__ < 10
+/**
+ * No support for access attribute in GCC < 10.
+ */
+#define cx_attr_access(mode, ...)
+#else
+/**
+ * Helper macro to define access macros.
+ */
+#define cx_attr_access(mode, ...) __attribute__((__access__(mode, __VA_ARGS__)))
+#endif // __GNUC__ < 10
+#if __GNUC__ < 14
+/**
+ * No support for \c null_terminated_string_arg in clang or GCC below 14.
+ */
+#define cx_attr_cstr_arg(idx)
+#else
+/**
+ * The specified argument is expected to be a zero-terminated string.
+ *
+ * @param idx the index of the argument
+ */
+#define cx_attr_cstr_arg(idx) \
+    __attribute__((__null_terminated_string_arg__(idx)))
+#endif // __GNUC__ < 14
+#endif // __clang__
+
+
+/**
+ * Specifies that the function will only read through the given pointer.
+ *
+ * Takes one or two arguments: the index of the pointer and (optionally) the
+ * index of another argument specifying the maximum number of accessed bytes.
+ */
+#define cx_attr_access_r(...) cx_attr_access(__read_only__, __VA_ARGS__)
+
+/**
+ * Specifies that the function will read and write through the given pointer.
+ *
+ * Takes one or two arguments: the index of the pointer and (optionally) the
+ * index of another argument specifying the maximum number of accessed bytes.
+ */
+#define cx_attr_access_rw(...) cx_attr_access(__read_write__, __VA_ARGS__)
+
+/**
+ * Specifies that the function will only write through the given pointer.
+ *
+ * Takes one or two arguments: the index of the pointer and (optionally) the
+ * index of another argument specifying the maximum number of accessed bytes.
+ */
+#define cx_attr_access_w(...) cx_attr_access(__write_only__, __VA_ARGS__)
+
+#if __STDC_VERSION__ >= 202300L
+
+/**
+ * Do not warn about unused variable.
+ */
+#define cx_attr_unused [[maybe_unused]]
+
+/**
+ * Warn about discarded return value.
+ */
+#define cx_attr_nodiscard [[nodiscard]]
+
+#else // no C23
+
+/**
+ * Do not warn about unused variable.
+ */
+#define cx_attr_unused __attribute__((__unused__))
+
+/**
+ * Warn about discarded return value.
+ */
+#define cx_attr_nodiscard __attribute__((__warn_unused_result__))
+
+#endif // __STDC_VERSION__
+
+// ---------------------------------------------------------------------------
+//       Useful function pointers
+// ---------------------------------------------------------------------------
+
 /**
  * Function pointer compatible with fwrite-like functions.
  */
@@ -103,7 +256,7 @@
         size_t,
         size_t,
         void *
-);
+) cx_attr_nonnull;
 
 /**
  * Function pointer compatible with fread-like functions.
@@ -113,7 +266,11 @@
         size_t,
         size_t,
         void *
-);
+) cx_attr_nonnull;
+
+// ---------------------------------------------------------------------------
+//       Utility macros
+// ---------------------------------------------------------------------------
 
 /**
  * Determines the number of members in a static C array.
@@ -126,7 +283,10 @@
  */
 #define cx_nmemb(arr) (sizeof(arr)/sizeof((arr)[0]))
 
-// cx_szmul() definition
+// ---------------------------------------------------------------------------
+//       szmul implementation
+// ---------------------------------------------------------------------------
+
 #if (__GNUC__ >= 5 || defined(__clang__)) && !defined(CX_NO_SZMUL_BUILTIN)
 #define CX_SZMUL_BUILTIN
 
@@ -174,24 +334,18 @@
 
 #endif // cx_szmul
 
-// Compiler specific stuff
 
-#ifndef __GNUC__
-/**
- * Removes GNU C attributes where they are not supported.
- */
-#define __attribute__(x)
-#endif
+// ---------------------------------------------------------------------------
+//       Fixes for MSVC incompatibilities
+// ---------------------------------------------------------------------------
 
 #ifdef _MSC_VER
-
 // fix missing ssize_t definition
 #include <BaseTsd.h>
 typedef SSIZE_T ssize_t;
 
 // fix missing _Thread_local support
 #define _Thread_local __declspec(thread)
-
-#endif
+#endif // _MSC_VER
 
 #endif // UCX_COMMON_H