Is C++11's long long really at least 64 bits?

Question

It says here and here that type long long is at least as long as an int and has no fewer than 64 bits. I have been looking at the

Answer 1

The C++ standard references the C standard for this, see [c.limits]. LLONG_MAX is defined in <climits> with the same meaning as C's <limits.h>'s LLONG_MAX. And this is what C has to say:

5.2.4.2.1 Sizes of integer types <limits.h>

The values given below shall be replaced by constant expressions suitable for use in #if preprocessing directives. [...] Their implementation-defined values shall be equal or greater in magnitude (absolute value) to those shown, with the same sign.

[...]

-- maximum value for an object of type long long int

LLONG_MAX +9223372036854775807 // 2⁶³ -1

A signed type that must be capable of representing the value 9223372036854775807 requires 64 bits or more.