[cfe-dev] Disable #error?

Sean Silva silvas at purdue.edu
Wed Jan 15 09:30:36 PST 2014

On Wed, Jan 15, 2014 at 1:37 AM, Kim Gräsman <kim.grasman at gmail.com> wrote:

> On Tue, Jan 14, 2014 at 11:25 PM, Sean Silva <silvas at purdue.edu> wrote:
> >
> > I don't think anyone would be against adding a callback to PPCallbacks to
> > indicate what the error message is so you can get the data. However,
> being
> > able to affect the outcome of compilation from a PPCallbacks callback
> seems
> > unwise;
> Yes, I agree that decision does not belong in PPCallbacks. But it's
> tempting! :-)
> Actually, now that I think about it, Jacob's scenario is the exact
> opposite of mine: he seems to be parsing headers in isolation and I
> will always see the private header via its umbrella header.
> For me the #error will never trigger, but that also means I'll never
> get a PPCallback for it. I just want to scan for it and use it to
> connect the private header name to its umbrella.

Just use pp-trace on the lone header and pipe it into a 10-line Python
script. (once a #error callback is introduced in PPCallbacks, and it is
wired into pp-trace).

-- Sean Silva

> For Jacob it triggers all the time, and he doesn't care about it.
> Stripping out the #error before attempting to parse could be a
> solution.
> But it would sure be nice to be able to lean on Clang's parser.
> > For the purpose of simply collecting #error directives from TU's, it
> seems
> > like the simplest thing to do would be to use pp-trace (once there is a
> > #error callback in PPCallbacks) driven from a short script. You could
> even
> > do better than trying to extract the header name from the #error message:
> > just look for the dominating #ifdef and see where it is defined.
> Good idea, I'll save that for later!
> - Kim
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