diff -r 72e5432f6b42 -r c9b02747cfc5 src/cx/common.h
--- a/src/cx/common.h	Fri Nov 01 18:33:16 2024 +0100
+++ b/src/cx/common.h	Sat Nov 02 13:38:51 2024 +0100
@@ -126,6 +126,54 @@
  */
 #define cx_nmemb(arr) (sizeof(arr)/sizeof((arr)[0]))
 
+// cx_szmul() definition
+#if (__GNUC__ >= 5 || defined(__clang__)) && !defined(CX_NO_SZMUL_BUILTIN)
+#define CX_SZMUL_BUILTIN
+
+/**
+ * Alias for \c __builtin_mul_overflow.
+ *
+ * Performs a multiplication of size_t values and checks for overflow.
+ *
+ * @param a first operand
+ * @param b second operand
+ * @param result a pointer to a size_t, where the result should
+ * be stored
+ * @return zero, if no overflow occurred and the result is correct, non-zero
+ * otherwise
+ */
+#define cx_szmul(a, b, result) __builtin_mul_overflow(a, b, result)
+
+#else // no GNUC or clang bultin
+
+/**
+ * Performs a multiplication of size_t values and checks for overflow.
+  *
+ * @param a first operand
+ * @param b second operand
+ * @param result a pointer to a size_t, where the result should
+ * be stored
+ * @return zero, if no overflow occurred and the result is correct, non-zero
+ * otherwise
+ */
+#define cx_szmul(a, b, result) cx_szmul_impl(a, b, result)
+
+/**
+ * Performs a multiplication of size_t values and checks for overflow.
+ *
+ * This is a custom implementation in case there is no compiler builtin
+ * available.
+ *
+ * @param a first operand
+ * @param b second operand
+ * @param result a pointer to a size_t where the result should be stored
+ * @return zero, if no overflow occurred and the result is correct, non-zero
+ * otherwise
+ */
+int cx_szmul_impl(size_t a, size_t b, size_t *result);
+
+#endif // cx_szmul
+
 // Compiler specific stuff
 
 #ifndef __GNUC__