How to do portable 64 bit arithmetic, without compiler warnings

Question

I occasionally use 64 bit arithmetic in an open source C++ library of mine. I discovered that long long serves my purpose quite nicely. Even some 10 year old solari

Answer 1

You can also suppress the warning using gcc's "__extension__" feature, e.g.:

// No '-pedantic' warning/error.
__extension__ long long foo = 2;

// Exhibits '-pedantic' warning/error.
long long bar = 3

and the compile:

$ g++ -pedantic -fsyntax-only foo.cpp
foo.cpp:5: error: ISO C++ 1998 does not support 'long long'

Notice that only the last use of long long triggered the -pedantic error since no __extension__ was prepended. Regardless, I'd go with @Steve Jessop's suggestion of using int64_t instead.