Warning: "‘lo’ may be used uninitialized in this function" in `math_fsum` in `mathmodule.c`

[sobolevn]

Looks like that after 87d3bd0 we got a new warning:

Linked PRs

• gh-100873: Fix "‘lo’ may be used uninitialized in this function" warning in mathmodule.c #100881

[mdickinson]

This is a false positive; definitely not a bug, but there may be something we can do to silence the warning.

[ZeroIntensity]

If it's a false positive, could casting to void help?

[mdickinson]

The simple and quick fix would be to initialise lo to 0.0. Technically that might affect performance, but I very much doubt the effect would be measurable. The only reason I'd hesitate to just make that fix would be that if it's not clear to the compiler that lo isn't used uninitialized, then it's probably not clear to humans either. So there may be an opportunity to rework the code a bit to make it clearer to both humans and compilers. But that opportunity also comes with a risk of inadvertently breaking something.

So I think initialising lo to 0.0 at the point where it's declared is the way to go; we can always look at streamlining the algorithm code in a separate PR.