Re: [PATCH] Refactor rust-demangle to be independent of C++ demangling.

["Ian Lance Taylor via gcc-patches" <gcc-patches@gcc.gnu.org>]

On Fri, Nov 8, 2019 at 11:17 AM Eduard-Mihai Burtescu <eddyb@lyken.rs> wrote:
>
> On Fri, Nov 8, 2019, at 7:43 PM, Ian Lance Taylor wrote:
> > On Fri, Nov 8, 2019 at 9:02 AM Eduard-Mihai Burtescu <eddyb@lyken.rs> wrote:
> > >
> > > Ping #2 for https://gcc.gnu.org/ml/gcc-patches/2019-10/msg01830.html
> > > Original patch (without the early exit optimization): https://gcc.gnu.org/ml/gcc-patches/2019-10/msg01591.html
> >
> > Sorry for letting this slide.
> >
> > Do we need the CHECK_OR and ERROR_AND macros?  Is there anything like
> > those elsewhere in the libiberty or GCC sources?  I would rather than
> > have ordinary code than obscure macros.
>
> Good point, I was wondering about the macros but forgot to ask explicitly, they're the least usual (for C) part of this code, they arose from porting the demangler for the new format (most of which isn't even in the current patch) from Rust, where we have facilities for conveniently propagating errors, and I wanted to avoid using goto too much for this purpose.
>
> Looking at https://gist.github.com/eddyb/c41a69378750a433767cf53fe2316768#file-rust-demangle-c I can see:
> * 5 uses of ERROR_AND
> * 20 uses of CHECK_OR
>   * 7 of those are CHECK_OR (!rdm->errored, return ); which can just be if (rdm->errored) return;
>
> So in the final code there'd be ~18 places that would need to set rdm->errored = 1; (and then return or goto cleanup).
> That's not that bad, I guess, and I'd welcome any suggestions for how to clean up that.
>
> For this current patch, however, there's only 3 uses total, so the macros are definitely overkill.
> Assuming you'd want them removed, I took the liberty of doing that and here's the fixed patch:
>
> 2019-10-22  Eduard-Mihai Burtescu  <eddyb@lyken.rs>
> include/ChangeLog:
>         * demangle.h (rust_demangle_callback): Add.
> libiberty/ChangeLog:
>         * cplus-dem.c (cplus_demangle): Use rust_demangle directly.
>         (rust_demangle): Remove.
>         * rust-demangle.c (is_prefixed_hash): Rename to is_legacy_prefixed_hash.
>         (parse_lower_hex_nibble): Rename to decode_lower_hex_nibble.
>         (parse_legacy_escape): Rename to decode_legacy_escape.
>         (rust_is_mangled): Remove.
>         (struct rust_demangler): Add.
>         (peek): Add.
>         (next): Add.
>         (struct rust_mangled_ident): Add.
>         (parse_ident): Add.
>         (rust_demangle_sym): Remove.
>         (print_str): Add.
>         (PRINT): Add.
>         (print_ident): Add.
>         (rust_demangle_callback): Add.
>         (struct str_buf): Add.
>         (str_buf_reserve): Add.
>         (str_buf_append): Add.
>         (str_buf_demangle_callback): Add.
>         (rust_demangle): Add.
>         * rust-demangle.h: Remove.

This is OK.

Thanks.

Ian