[Bug middle-end/87220] -fstack-check produces inefficient and wrong tests

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87220

--- Comment #7 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Eric, even accepting the purpose in 1, what I described in 2 seems like a
> bug. If it needs an extra page past what's actually used, it needs to make
> one probe in the last-used page to ensure it doesn't jump a guard page.

Not if it's caller has done so for it though.

> Anyway, I'll accept that this feature just isn't useful for what I wanted it
> for, but I agree with Alexander that it should be clearly documented that
> not only is it not intended for this purpose, but it fails to perform this
> purpose at all and can even introduce new jump-the-guard-page conditions
> that would not have been present without the option.

We cannot reasonably document that a feature does exactly the opposite of what
it is intended to do, can we?  You need to compile the entire software with the
option, that's all.