How to silence long long integer constant warning from GCC

Question

I have some code using large integer literals as follows:

if(nanoseconds < 1'000'000'000'000)

This gives the compiler warning integer constant is too large for 'long' type [-Wlong-long]. However, if I change it to:

if(nanoseconds < 1'000'000'000'000ll)

...I instead get the warning use of C++11 long long integer constant [-Wlong-long].

I would like to disable this warning just for this line, but without disabling -Wlong-long or using -Wno-long-long for the entire project. I have tried surrounding it with:

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wlong-long"
...
#pragma GCC diagnostic pop

but that does not seem to work here with this warning. Is there something else I can try?

I am building with -std=gnu++1z.

Edit: minimal example for the comments:

#include <iostream>
auto main()->int {
  double nanoseconds = 10.0;
  if(nanoseconds < 1'000'000'000'000ll) {
    std::cout << "hello" << std::endl;
  }
  return EXIT_SUCCESS;
}

Building with g++ -std=gnu++1z -Wlong-long test.cpp gives test.cpp:6:20: warning: use of C++11 long long integer constant [-Wlong-long]

I should mention this is on a 32bit platform, Windows with MinGW-w64 (gcc 5.1.0) - the first warning does not seem to appear on my 64bit Linux systems, but the second (with the ll suffix) appears on both.

Answer 1

It seems that the C++11 warning when using the ll suffix may be a gcc bug. (Thanks @praetorian)

A workaround (inspired by @nate-eldredge's comment) is to avoid using the literal and have it produced at compile time with constexpr:

int64_t constexpr const trillion = int64_t(1'000'000) * int64_t(1'000'000);
if(nanoseconds < trillion) ...