Is there a standard way to determine at compile-time if system is 32 or 64 bit?

Question

I need to set #ifdef - checks for conditional compile. I want to automate the process but cannot specify the target OS/machine. Is there some way that the pre-compiler can resolve whether it it is running on 32-bit or 64-bit?

(Explanation) I need to define a type that is 64 bits in size. On 64bit OS it is a long, on most others it is a long long.

I found this answer - is this the correct way to go?

[edit] a handy reference for compiler macros

Answer 1

The only compile check you can do reliably would be sizeof(void*) == 8, true for x64 and false for x86. This is a constexpr and you can pass it to templates but you can forget using ifdef with it. There is no platform-independent way to know the address size of the target architecture (at pre-process time), you will need to ask your IDE for one. The Standard doesn't even have the concept of the address size.