Re: Casting function pointers


"David Brown" <david@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message news:47a1a698$0$14997$8404b019@xxxxxxxxxxxxxxxxxx
KKL wrote:
I wonder how casting with function pointers work, how it "should be"
handled and how it "should not be" handled. Can anyone tell whether
the below code should work or not?

<snip>
My question is whether these kind of casting for function pointers is
valid. If valid should it work with a predictable behavior or the
behavior is undefined.


It's also important to note that function pointers are not directly compatible with data pointers - you can't
necessarily convert a function pointer to a void* and back again, and expect a valid result (although it should work
in practice, at least on 32-bit processors). You can't ever convert a method pointer to a function pointer (unless
it's a static method).

Correct. Both pointer to member and pointer to method typically have
a completely different meaning and representation to normal pointers,
including a different bitpattern to represent the null pointer (the 0 value
is already used for offset 0 or the first virtual function). Since there is
a lot more complexity in C++, different C++ compilers all do something
different (and binary incompatible) - except when adhering to a common
ABI.

C function pointers and data pointers are best not mixed.

Wilco


.

Relevant Pages

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