The implementation of "const" in C/C++ is really annoying, in the end all you get is a bit of semantic documentation and a bunch of compiler errors or casts whenever some library doesn't use it. You can often trick the compiler into stronger optimizations by making a local variable marked as "const" (in which case it is a "true const") and copying the value to/from it.
The real problem is that "const" in C/C++ is a misnomer - the literal meaning of the word means "unchanging", and yet if you have a pointer or reference to a const T, it can, in fact, change. A "const pointer" in C is really a read-only pointer to some data that may or may not be actually constant.
In C, at least, you can usually distinguish a true pointer to immutable data by using `restrict`.
