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Re: [patch] PR debug/46102 Disable -feliminate-dwarf2-dups when reading a PCH


On Thu, Feb 19, 2015 at 10:33:20AM -0800, Aldy Hernandez wrote:
> Well, any PCH file we generate will have some sort of early DIE in it (at
> the very least the compilation unit DIE) and we will read these in at PCH
> read-in time, obliterating whatever was already there.  But most
> importantly, with the attached patch we will not use these
> DW_TAG_GNU_[BE]INCL* DIEs, since the reader will avoid reading the pch file.
> So, I don't think erroring out at output time is necessary.
> 
> How does this look?

Looks reasonable to me, but I'd prefer to defer this to Jason as debug
maintainer.

> commit d90a408ad21aa0868cc13de24ea38e210ef78a68
> Author: Aldy Hernandez <aldyh@redhat.com>
> Date:   Thu Feb 19 07:35:59 2015 -0800
> 
>     	PR debug/46102
>     	* c-pch.c (c_common_valid_pch): Mark PCH file with
>     	-feliminate-dwarf2-dups as invalid.
> 
> diff --git a/gcc/c-family/c-pch.c b/gcc/c-family/c-pch.c
> index 0ede92a..55163c9 100644
> --- a/gcc/c-family/c-pch.c
> +++ b/gcc/c-family/c-pch.c
> @@ -224,6 +224,19 @@ c_common_valid_pch (cpp_reader *pfile, const char *name, int fd)
>    const char *pch_ident;
>    struct c_pch_validity v;
>  
> +  /* We may have outputted a few DIEs corresponding to
> +     DW_TAG_GNU_[BE]INCL.  Reading the compiler state later will read
> +     in these DIEs, and obliterate any DW_TAG_GNU_[BE]INCL the reader
> +     may have generated itself.  Do not read the PCH if this may
> +     happen.  */
> +  if (flag_eliminate_dwarf2_dups)
> +    {
> +      if (cpp_get_options (pfile)->warn_invalid_pch)
> +	cpp_error (pfile, CPP_DL_WARNING,
> +		   "%s: cannot be used with -feliminate-dwarf2-dups", name);
> +      return 2;
> +    }
> +
>    /* Perform a quick test of whether this is a valid
>       precompiled header for the current language.  */
>  


	Jakub


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