Quuxplusone
commented
13 years ago (In reply to comment #0)
> Consider the following input:
>
> int foo = 1 > 2 ? 1 << -1 : 0;
>
> This results in a warning about the negative shift, even if that branch of the
> ternary operator is known to be unused. This does work inside a function e.g.
> as statement.
We currently don't construct control-flow graphs (CFGs) when processing
initializer expressions in a global context. CFGs have been used for doing a
variety of flow-based warnings in functions, but at this point they haven't
been used for global initializer expressions.
Doing the same kind of warning suppression for global initializers would be
doable using CFGs. If we did so, I'd argue that we lazily construct the CFGs,
and only do the analysis for suppressing such warnings when necessary.
Constructing the CFGs all the time would be cost prohibitive.
That said, I somewhat question the value in doing this, although I can see how
warnings for cases like the above are a result of macro expansion.
Consider the following input:
int foo = 1 > 2 ? 1 << -1 : 0;
This results in a warning about the negative shift, even if that branch of the ternary operator is known to be unused. This does work inside a function e.g. as statement.