Re: [PATCH] preprocessor: Reinitialize frontend parser after loading a PCH [PR112319]

[Lewis Hyatt <lhyatt@gmail.com>]

On Thu, Nov 30, 2023 at 4:19 PM Marek Polacek <polacek@redhat.com> wrote:
>
> On Wed, Nov 01, 2023 at 05:54:57PM -0400, Lewis Hyatt wrote:
> > Hello-
> >
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112319
> >
> > This is a one-line patch to fix the GCC 14 regression noted in the
> > PR. Bootstrap + regtest all languages on x86-64 looks good. Is it OK please?
> > Thanks!
> >
> > -Lewis
> >
> > -- >8 --
> >
> > Since r14-2893, the frontend parser object needs to exist when running in
> > preprocess-only mode, because pragma_lex() is now called in that mode and
> > needs to make use of it. This is handled by calling c_init_preprocess() at
> > startup. If -fpch-preprocess is in effect (commonly, because of
> > -save-temps), a PCH file may be loaded during preprocessing, in which
> > case the parser will be destroyed, causing the issue noted in the
> > PR. Resolve it by reinitializing the frontend parser after loading the PCH.
> >
> > gcc/c-family/ChangeLog:
> >
> >       PR pch/112319
> >       * c-ppoutput.cc (cb_read_pch): Reinitialize the frontend parser
>
> "front-end"
>
> >       after loading a PCH.
> >
> > gcc/testsuite/ChangeLog:
> >
> >       PR pch/112319
> >       * g++.dg/pch/pr112319.C: New test.
> >       * g++.dg/pch/pr112319.Hs: New test.
> >       * gcc.dg/pch/pr112319.c: New test.
> >       * gcc.dg/pch/pr112319.hs: New test.
> > ---
> >  gcc/c-family/c-ppoutput.cc           | 5 +++++
> >  gcc/testsuite/g++.dg/pch/pr112319.C  | 5 +++++
> >  gcc/testsuite/g++.dg/pch/pr112319.Hs | 1 +
> >  gcc/testsuite/gcc.dg/pch/pr112319.c  | 5 +++++
> >  gcc/testsuite/gcc.dg/pch/pr112319.hs | 1 +
> >  5 files changed, 17 insertions(+)
> >  create mode 100644 gcc/testsuite/g++.dg/pch/pr112319.C
> >  create mode 100644 gcc/testsuite/g++.dg/pch/pr112319.Hs
> >  create mode 100644 gcc/testsuite/gcc.dg/pch/pr112319.c
> >  create mode 100644 gcc/testsuite/gcc.dg/pch/pr112319.hs
> >
> > diff --git a/gcc/c-family/c-ppoutput.cc b/gcc/c-family/c-ppoutput.cc
> > index 4aa2bef2c0f..4f973767976 100644
> > --- a/gcc/c-family/c-ppoutput.cc
> > +++ b/gcc/c-family/c-ppoutput.cc
> > @@ -862,4 +862,9 @@ cb_read_pch (cpp_reader *pfile, const char *name,
> >
> >    fprintf (print.outf, "#pragma GCC pch_preprocess \"%s\"\n", name);
> >    print.src_line++;
> > +
> > +  /* The process of reading the PCH has destroyed the frontend parser,
>
> "front-end"
>
> > +     so ask the frontend to reinitialize it, in case we need it to
>
> "front end"
>
> (sorry to be overly pedantic...)
>
> Patch looks fine to me; please go ahead if you haven't pushed it already.
>

Thanks for the review! I did push it a few days ago as Jakub approved
it... I will spell front end correctly next time :).

-Lewis