Problems with header files and namespaces

[mreineck]

More or less by accident, I saw the following warning in one of the finufft CI logs today:

Warning: /home/runner/work/finufft/finufft/test/testutils.cpp:86:7: warning: using integer absolute value function 'abs' when argument is of floating point type [-Wabsolute-value]

This is bad. It means that abs is called on a floating point argument without having included <math.h> (<cmath> doesn't count - it only provides std::abs). As a consequence, the argument to abs will be truncated to integer, which is definitely not wanted.

Suggested workaround: always use std::abs and make sure that <cmath> is included.

(I'm not sure why "IWYU" is not catching this; but abs is a special case since it can show up in different system headers with different semantics ...)

[DiamonDinoia]

Hi @mreineck,

Thanks for pointing it out! I will have a look. I think the reason of not using std::abs is that it breaks with CUDA. I might need to do an ifdef and use trust::abs. Maybe including math.h does the trick.

PS:

I only run IWYU locally not in CI. I am waiting for a moment where there are no pending PR to fix all the includes since it will cause conflicts...

[mreineck]

Is nvcc complaining when cmath is included? This feels worrying ...