On 08/06/2017 01:59 AM, Boris Kolpackov wrote:
> Hi,
> Currently GCC does not write extracted header dependency information
> if there are errors. However, this can be useful when dealing with
> outdated generated headers that trigger errors which would have been
> resolved if we could update it. A concrete example in our case is a
> version check with #error.
> The included (trivial) patch changes this behavior. Note also that
> this is how Clang already behaves. I've tested the patch in build2
> and everything works well (i.e., no invalid dependency output in the
> face of various preprocessor errors such as #error, stray #else, etc).
> While I don't foresee any backwards-compatibility issues with such
> an unconditional change (after all, the compiler still exists with
> an error status), if there are concerns, I could re-do it via an
> option (e.g., -ME, analogous to -MG).
> P.S. I have the paperwork necessary to contribute on file with FSF.
This directly reverts part of Joseph's changes from 2009.   I'd like to
hear from him on this change.

commit 7f5f395354b35ab7f472d03dbcce1301ac4f8257
Author: jsm28 <jsm28@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Sun Mar 29 22:56:07 2009 +0000

            PR preprocessor/34695

[ ... ]
    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@145263

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