[mrguyorama]

The fact that -ffast-math makes no mention that it will poison any other code executing in your process space is a huge missing point of info. Docs as written, anyone not doing scientific math should have that flag, but the reality is that most people have some code somewhere in their process that expects fairly sane floating point math behavior, even if it's just displaying progress bars or something.

[nsajko]

> The fact that -ffast-math makes no mention that it will poison any other code executing in your process space

Untrue. The doc entry for -ffast-math says "can result in incorrect output for programs that depend on an exact implementation of IEEE or ISO rules/specifications for math functions". Emphasis mine.

So they clearly say that the entire program can turn invalid when -ffast-math is used.

You and some other people here act like the docs say "translation unit" or something like that, instead of "program", but this is simply not the case.

Furthermore, the entry for -ffast-math points to entries for suboptions that -ffast-math turns on (located right below in the man page), e.g. -funsafe-math-optimization. These also make clear how dangerous they can be even when turned on one at a time.

[tomrod]

How many programs do you deal with daily that you don't anticipate to follow ISO/IEEE?

[account42]

Most don't really care that much.

[pixl97]

Me: of course I want the FUN SAFE optimization.

They: Sir, that is dash F unsafe!