Re: [PATCH] avoid warning on constant strncpy until next statement is reachable (PR 87028)

[Joseph Myers <joseph@codesourcery.com>]

On Thu, 4 Oct 2018, Jeff Law wrote:

> With the natural tensions around warning early vs warning late the
> warning analysis phase may choose to mark statements in various ways
> rather than issuing the warning at that time.  ie, it might choose to
> mark the statement with the set of potential issues as well as marking
> those which were proven safe.  A later pass could then refine things and
> issue the actual warning.  Or something like that.

Note that could include front ends marking expressions for warning issues 
as well.  (E.g. the signed/unsigned warnings, which fold and do some crude 
checks for cases where they can prove the signed value is never negative.)  
To avoid that front-end folding you want later code outside the front end 
to have the information that there was a (comparison / implicit conversion 
from signed to unsigned) that should be warned about if the later code 
can't prove the conversion was value-preserving.

-- 
Joseph S. Myers
joseph@codesourcery.com