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

[Marek Polacek <polacek@redhat.com>]

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.

> +     process any #pragma directives encountered while preprocessing.  */
> +  c_init_preprocess ();
>  }
> diff --git a/gcc/testsuite/g++.dg/pch/pr112319.C b/gcc/testsuite/g++.dg/pch/pr112319.C
> new file mode 100644
> index 00000000000..9e0457e8aec
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/pch/pr112319.C
> @@ -0,0 +1,5 @@
> +/* { dg-additional-options "-Wpragmas -save-temps" } */
> +#include "pr112319.H"
> +#pragma GCC diagnostic error "-Wpragmas"
> +#pragma GCC diagnostic ignored "oops" /* { dg-error "oops" } */
> +/* { dg-regexp {[^[:space:]]*: some warnings being treated as errors} } */
> diff --git a/gcc/testsuite/g++.dg/pch/pr112319.Hs b/gcc/testsuite/g++.dg/pch/pr112319.Hs
> new file mode 100644
> index 00000000000..3b6178bfae0
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/pch/pr112319.Hs
> @@ -0,0 +1 @@
> +/* This space intentionally left blank.  */
> diff --git a/gcc/testsuite/gcc.dg/pch/pr112319.c b/gcc/testsuite/gcc.dg/pch/pr112319.c
> new file mode 100644
> index 00000000000..043881463c5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pch/pr112319.c
> @@ -0,0 +1,5 @@
> +/* { dg-additional-options "-Wpragmas -save-temps" } */
> +#include "pr112319.h"
> +#pragma GCC diagnostic error "-Wpragmas"
> +#pragma GCC diagnostic ignored "oops" /* { dg-error "oops" } */
> +/* { dg-regexp {[^[:space:]]*: some warnings being treated as errors} } */
> diff --git a/gcc/testsuite/gcc.dg/pch/pr112319.hs b/gcc/testsuite/gcc.dg/pch/pr112319.hs
> new file mode 100644
> index 00000000000..3b6178bfae0
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pch/pr112319.hs
> @@ -0,0 +1 @@
> +/* This space intentionally left blank.  */
> 

Marek