Issue with LTO/-fwhole-program

[Ian Lance Taylor]

Manuel López-Ibáñez <lopezibanez@gmail.com> writes:

> This also means that linking your program with non-LTO+whole-program
> code may lead to miscompilations without any warning, which is really
> bad. I don't think it is a reasonable limitation and we will get bad
> press when programs start breaking for users. They won't care (and
> they won't even listen) about the reasons. The conclusion will be: LTO
> is broken in GCC, and just use another compiler.

The limitation isn't all that bad.  If you want to use
-fwhole-program, I think the basic rule is this: compile all your code
with -flto, and don't define variables or functions which are
referenced by any code which is not yours.

I think adding a warning for this case would be great, if we can
figure out how to do it.  But I also think that a clear statement in
the documentation will avoid most user problems.

Ian