Index: docs/UsersManual.rst
===================================================================
--- docs/UsersManual.rst
+++ docs/UsersManual.rst
@@ -1098,6 +1098,14 @@
    the behavior of sanitizers in the ``cfi`` group to allow checking
    of cross-DSO virtual and indirect calls.
 
+.. option:: -f[no-]strict-aliasing
+
+   Enables/disables the strict aliasing assumption, which assumes that
+   objects of different types do not share the same location in memory.
+
+   NOTE: Unlike gcc, clang does not allow "type-punning" by writing and
+   reading from different union members without `-fno-strict-aliasing`
+   enabled.
 
 .. option:: -fstrict-vtable-pointers