Re: [PATCH] Check endianess detection.

["H.J. Lu" <hjl.tools@gmail.com>]

On Mon, Mar 23, 2020 at 8:39 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Mon, Mar 23, 2020 at 4:07 PM Martin Liška <mliska@suse.cz> wrote:
> >
> > Hi.
> >
> > There's a patch draft that will do the proper versioning of API.
>
> Would sth like this be preferred on the binutils side or would
> splitting up the 'def' field via shift&masking better?
>
> @@ -87,25 +87,30 @@ struct ld_plugin_symbol
>  {
>    char *name;
>    char *version;
> -  /* This is for compatibility with older ABIs.  The older ABI defined
> -     only 'def' field.  */
> -#ifdef __BIG_ENDIAN__
> -  char unused;
> ...
> +  int def;
>    int visibility;
>    uint64_t size;
>    char *comdat_key;
>    int resolution;
>  };
>
> +/* A symbol belonging to an input file managed by the plugin library
> +   (version 2).  */
> +
> +struct ld_plugin_symbol_v2
> +{
> +  char *name;
> +  char *version;
> +  int def;
> +  int visibility;
> +  uint64_t size;
> +  char *comdat_key;
> +  int resolution;
> +  char symbol_type;
> +  char section_kind;
> +  uint16_t unused;
> +};
>
> I think for ease of use you should do
>
> struct ld_plugin_symbol_v2
> {
>   ld_plugin_symbol v1_data;
>   char symbol_type;
>   char section_kind;
>   uint16_t unused;
> }
>
> also please avoid 'char', either use uint8_t or
> at least unsigned char.  I guess since you're extending
> the type anyway using two plain 'int' would better follow
> the rest of the data structure.
>
> > It's a subject for discussion.
>
> -       status = add_symbols_v2 (file->handle, lto_file.symtab.nsyms,
> -                                lto_file.symtab.syms);
> +       {
> +         /* Merge symtab::syms and symtab::syms_v2 data.  */
> +         for (unsigned int i = 0; i < lto_file.symtab.nsyms; i++)
> +           {
>
> I think lto-plugin should internally always parse into the "full" format,
> using defaults for entries not in IL files.  Only the interfacing with
> the linker should then decide.

Can we use

#if __has_include (<endian.h>)
...
#ifdef __BYTE_ORDER
#if __BYTE_ORDER == __BIG_ENDIAN
...

We support V2 interface only if <endian.h> defines __BYTE_ORDER?


-- 
H.J.