C++: int64_t where does it come from?

Question

I was wondering where types like int64_t come from. Are they c++ standard or os-dependent? (1)

Also, do you know where I can find documentation about these types? I couldn't find useful information so far. Do they have a special name? (2)

What's their general difference with regards to the standard primitive types like int,long... (3)

Thank you and Regards

See [this related SO question](http://stackoverflow.com/questions/13604137/definition-of-int64-t). — juanchopanza, Dec 25 '13 at 13:27
Looking for [this](http://en.cppreference.com/w/cpp/types/integer) ? — P0W, Dec 25 '13 at 13:28
The types are only conditionally defined if the platform is able to provide the guarantees they make. — Kerrek SB, Dec 25 '13 at 14:00

score 5 · Answer 1 · answered Dec 25 '13 at 13:28

5

It comes from a header file:

#include <stdint.h> // C standard library
#include <cstdint> // C++ standard library

answered Dec 25 '13 at 13:28

egur

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score 4 · Answer 2 · answered Dec 25 '13 at 13:28

4

int64_t is typedef you can find that in

   <cstdint>

answered Dec 25 '13 at 13:28

user3134167

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bolov · Accepted Answer · 2013-12-25T15:07:52.807

They were introduced by C99 standard.

Documentation:
http://www.cplusplus.com/reference/cstdint/
http://en.cppreference.com/w/c/types/integer

They were introduced because the standard doesn't specify fixed width for standard primitives, but a minimum width. So int can be 16-bit or 32-bit, depending on compiler, OS, and architecture, long varies as well as it can be 32-bit or 64-bit. Even char can be 8 or 16 bits.

C++: int64_t where does it come from?

3 Answers3