sizeof in compilation time

[ricardo.crudo]

I need know what is the size of a address of one variable, in other words, how much bytes I need to store the address of a variable (in compilation time).

Unhappily not is possible use sizeof in define pre-processors, like this:

#define ADDRESS_SIZE    sizeof(void *)

So, I try this:

#define ADDRESS_SIZE   ((char *)((void**)0 + 1) - (char*)(void**)0)

Apparently this work but, in this way I cannot do this test:

#if ADDRESS_SIZE == 4
typedef uint32_t address_pointer;
#endif

#if ADDRESS_SIZE == 8
typedef uint64_t address_pointer;
#endif

This return the error: "operator '*' don't have operator to right"

Can anyone help me with this problem?

Thanks,
Ricardo.

[L7Sqr]

sizeof is a compile-time operation. The #if is part of the translation phase (which happens before compilation). So you can not use the compiled results before it is computed.

You can either use a type that is designed for this already ( uintptr_t ) or have your build system pass the value in as a compiler option ( -DADDRESS_SIZE=8 with gcc, for example).

[ricardo.crudo]

Thank you.