[PATCH 2/2] Specialize partial_symtab for DWARF include files

[Simon Marchi]

On 2020-02-25 8:09 a.m., Tom Tromey wrote:
> Include files are represented by a partial symtab, but don't expand to
> anything.  From dwarf2_psymtab::expand_psymtab:
> 
>   if (per_cu == NULL)
>     {
>       /* It's an include file, no symbols to read for it.
>          Everything is in the parent symtab.  */
>       readin = true;
>       return;
>     }
> 
> This patch introduces a new specialization of partial_symtab to handle
> this case.  In addition to being slightly smaller, I believe an
> include file is the only situation where a DWARF psymtab can result in
> a null compunit_symtab.  This adds an assert to that effect as well.
> This change will simplify one of the psymtab sharing patches.
> 
> gdb/ChangeLog
> 2020-02-25  Tom Tromey  <tom@tromey.com>
> 
> 	* dwarf2/read.c (struct dwarf2_include_psymtab): New.
> 	(dwarf2_create_include_psymtab): Use dwarf2_include_psymtab.
> 	(dwarf2_psymtab::expand_psymtab, dwarf2_psymtab::readin_p)
> 	(dwarf2_psymtab::get_compunit_symtab): Remove null checks for
> 	per_cu_data.

Hi Tom,

>From what I understand, this is fine, thanks.

> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
> index 8c40ddb727a..d22a53deb25 100644
> --- a/gdb/dwarf2/read.c
> +++ b/gdb/dwarf2/read.c
> @@ -5894,6 +5894,45 @@ read_abbrev_offset (struct dwarf2_per_objfile *dwarf2_per_objfile,
>    return (sect_offset) read_offset (abfd, info_ptr, offset_size);
>  }
>  
> +/* A partial symtab that is used only for include files.  */
> +struct dwarf2_include_psymtab : public partial_symtab
> +{
> +  dwarf2_include_psymtab (const char *filename, struct objfile *objfile)
> +    : partial_symtab (filename, objfile)
> +  {
> +  }
> +
> +  void read_symtab (struct objfile *objfile) override
> +  {
> +    expand_psymtab (objfile);
> +  }
> +
> +  void expand_psymtab (struct objfile *objfile) override
> +  {
> +    if (m_readin)
> +      return;
> +    /* It's an include file, no symbols to read for it.
> +       Everything is in the parent symtab.  */
> +    read_dependencies (objfile);
> +    m_readin = true;
> +  }
> +
> +  bool readin_p () const override
> +  {
> +    return m_readin;
> +  }
> +
> +  struct compunit_symtab *get_compunit_symtab () const
> +    override

The override can be on the previous line.

Simon