Re: [PATCH] libcpp: Diagnose #include after failed __has_include [PR80753]

[Jason Merrill <jason@redhat.com>]

On 6/13/23 12:29, Jakub Jelinek wrote:
> Hi!
> 
> As can be seen in the testcase, we don't diagnose #include/#include_next
> of a non-existent header if __has_include/__has_include_next is done for
> that header first.
> The problem is that we normally error the first time some header is not
> found, but in the _cpp_FFK_HAS_INCLUDE case obviously don't want to diagnose
> it, just expand it to 0.  And libcpp caches both successful includes and
> unsuccessful ones.
> 
> The following patch fixes that by remembering that we haven't diagnosed
> error when using __has_include* on it, and diagnosing it when using the
> cache entry in normal mode the first time.
> 
> I think _cpp_FFK_NORMAL is the only mode in which we normally diagnose
> errors, for _cpp_FFK_PRE_INCLUDE that open_file_failed isn't reached
> and for _cpp_FFK_FAKE neither.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk and
> after a while for backports?

OK.

> 2023-06-13  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR preprocessor/80753
> libcpp/
> 	* files.cc (struct _cpp_file): Add deferred_error bitfield.
> 	(_cpp_find_file): When finding a file in cache with deferred_error
> 	set in _cpp_FFK_NORMAL mode, call open_file_failed and clear the flag.
> 	Set deferred_error in _cpp_FFK_HAS_INCLUDE mode if open_file_failed
> 	hasn't been called.
> gcc/testsuite/
> 	* c-c++-common/missing-header-5.c: New test.
> 
> --- libcpp/files.cc.jj	2023-01-16 11:52:16.326730483 +0100
> +++ libcpp/files.cc	2023-06-13 11:27:59.867465878 +0200
> @@ -109,6 +109,10 @@ struct _cpp_file
>     /* If this file is implicitly preincluded.  */
>     bool implicit_preinclude : 1;
>   
> +  /* Set if a header wasn't found with __has_include or __has_include_next
> +     and error should be emitted if it is included normally.  */
> +  bool deferred_error : 1;
> +
>     /* > 0: Known C++ Module header unit, <0: known not.  ==0, unknown  */
>     int header_unit : 2;
>   };
> @@ -523,7 +527,14 @@ _cpp_find_file (cpp_reader *pfile, const
>     cpp_file_hash_entry *entry
>       = search_cache ((struct cpp_file_hash_entry *) *hash_slot, start_dir);
>     if (entry)
> -    return entry->u.file;
> +    {
> +      if (entry->u.file->deferred_error && kind == _cpp_FFK_NORMAL)
> +	{
> +	  open_file_failed (pfile, entry->u.file, angle_brackets, loc);
> +	  entry->u.file->deferred_error = false;
> +	}
> +      return entry->u.file;
> +    }
>   
>     _cpp_file *file = make_cpp_file (start_dir, fname);
>     file->implicit_preinclude
> @@ -589,6 +600,8 @@ _cpp_find_file (cpp_reader *pfile, const
>   
>   	    if (kind != _cpp_FFK_HAS_INCLUDE)
>   	      open_file_failed (pfile, file, angle_brackets, loc);
> +	    else
> +	      file->deferred_error = true;
>   	    break;
>   	  }
>   
> --- gcc/testsuite/c-c++-common/missing-header-5.c.jj	2023-06-13 11:29:49.345931030 +0200
> +++ gcc/testsuite/c-c++-common/missing-header-5.c	2023-06-13 11:25:34.952497526 +0200
> @@ -0,0 +1,15 @@
> +/* PR preprocessor/80753 */
> +/* { dg-do compile } */
> +/* { dg-options "" } */
> +
> +#if __has_include("nonexistent.h")
> +# error
> +#endif
> +
> +#include "nonexistent.h"
> +
> +/* { dg-message "nonexistent.h" "nonexistent.h" { target *-*-* } 0 } */
> +/* { dg-message "terminated" "terminated" { target *-*-* } 0 } */
> +
> +/* This declaration should not receive any diagnostic.  */
> +foo bar;
> 
> 	Jakub
>