Fix documentation
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/bignum_core.h b/library/bignum_core.h
index b3d05a3..158d2b3 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -102,9 +102,12 @@
/** Count leading zero bits in a given integer.
*
+ * \warning The result is undefined if \p a == 0
+ *
* \param a Integer to count leading zero bits.
*
- * \return The number of leading zero bits in \p a.
+ * \return The number of leading zero bits in \p a, if \p a != 0.
+ * If \p a == 0, the result is undefined.
*/
size_t mbedtls_mpi_core_clz(mbedtls_mpi_uint a);