Andrew Haley wrote:
You are allowed to take a pointer, copy it as a void *, and copy it
back to the same type and dereference it. If the compiler removes
the copy step, then the compiler is broken. If your code accesses
the object via an incompatible type, then your code is broken.
I think the difference between that and what I'm doing is the extra
level of indirection.
I write a Datatype* indirectly through a Datatype**. Then I read a
void* indirectly through a void** that happens to be the same pointer as
that Datatype**.
Next I do the reverse (write through void** to read through Datatype**).
You're saying I can copy a Datatype* to a void* then back to a Datatype*
and use it. That wouldn't be a violation of strict aliasing, because it
never dereferences two different type pointers to the same address.
I know my code is "broken". I didn't write it and I have no practical
way to rewrite it. I'm looking for a local work around to the problem.
I've looked at the generated assembler code and the copy step is
optimized out when compiled without -fno-strict-alias and isn't
optimized out when compiled with -fno-strict-alias.
