Preprocessor macro to identify 64bit

Question

Is there a gcc macro that allows me to identify whether something is being compiled in 64bit mode?

http://stackoverflow.com/questions/5272825/detecting-64bit-compile-in-c — pna, Dec 07 '11 at 01:50
Possible duplicate of [Detecting 64bit compile in C](https://stackoverflow.com/q/5272825/608639) — jww, Nov 26 '18 at 04:15

score 3 · Accepted Answer · edited May 23 '17 at 10:30

3

__LP64__ Seems to be what you want.

edited May 23 '17 at 10:30

Community

answered Dec 07 '11 at 01:50

Daniel Placek

1

Note that on Windows, 64bit compiles are indicated by `__LLP64__` (yes, even with `gcc`). See http://blogs.msdn.com/b/oldnewthing/archive/2005/01/31/363790.aspx for details. – FrankH. Dec 09 '11 at 14:42

score 1 · Answer 2 · answered Dec 07 '11 at 06:00

And you could also, at least on Linux,

  #include <features.h>
  #include <endian.h>    // perhaps you skip that
  #include <limits.h>
  #include <stdint.h>

Then <bits/workdsize.h> gets included and gives you __WORDSIZE (either 64 or 32)

But why do you ask and why using the standard types provided by <stdint.h> is not enough for you?

2 Answers2