Re: [PATCHv3] libiberty rust-demangle, ignore .suffix

[Mark Wielaard <mark@klomp.org>]

Ping. Is this OK to commit now?
I am not sure who can approve this.

On Sun, Jan 16, 2022 at 01:35:34AM +0100, Mark Wielaard wrote:
> Rust symbols can have a .suffix because of compiler transformations.
> These can be ignored in the demangled name. Which is what this patch
> implements. By stopping at the first dot for v0 symbols and searching
> backwards to the ending 'E' for legacy symbols.
> 
> An alternative implementation could be to follow what C++ does and
> represent these as [clone .suffix] tagged onto the demangled name.
> But this seems somewhat confusing since it results in a demangled
> name that cannot be mangled again. And it would mean trying to
> decode compiler internal naming.
> 
> https://bugs.kde.org/show_bug.cgi?id=445916
> https://github.com/rust-lang/rust/issues/60705
> 
> libiberty/Changelog
> 
> 	* rust-demangle.c (rust_demangle_callback): Ignore everything
> 	after '.' char in sym for v0. For legacy symbols search
> 	backwards to find the last 'E' before any '.'.
> 	* testsuite/rust-demangle-expected: Add new .suffix testcases.
> ---
>  libiberty/rust-demangle.c                  | 21 ++++++++++++++---
>  libiberty/testsuite/rust-demangle-expected | 26 ++++++++++++++++++++++
>  2 files changed, 44 insertions(+), 3 deletions(-)
> 
> V3 - Add more testcases
>    - Allow @ in legacy symbols (which can appear in the .suffix)
> 
> diff --git a/libiberty/rust-demangle.c b/libiberty/rust-demangle.c
> index 18c760491bdc..42c88161da30 100644
> --- a/libiberty/rust-demangle.c
> +++ b/libiberty/rust-demangle.c
> @@ -1340,13 +1340,19 @@ rust_demangle_callback (const char *mangled, int options,
>    /* Rust symbols (v0) use only [_0-9a-zA-Z] characters. */
>    for (p = rdm.sym; *p; p++)
>      {
> +      /* Rust v0 symbols can have '.' suffixes, ignore those.  */
> +      if (rdm.version == 0 && *p == '.')
> +        break;
> +
>        rdm.sym_len++;
>  
>        if (*p == '_' || ISALNUM (*p))
>          continue;
>  
> -      /* Legacy Rust symbols can also contain [.:$] characters. */
> -      if (rdm.version == -1 && (*p == '$' || *p == '.' || *p == ':'))
> +      /* Legacy Rust symbols can also contain [.:$] characters.
> +         Or @ in the .suffix (which will be skipped, see below). */
> +      if (rdm.version == -1 && (*p == '$' || *p == '.' || *p == ':'
> +                                || *p == '@'))
>          continue;
>  
>        return 0;
> @@ -1355,7 +1361,16 @@ rust_demangle_callback (const char *mangled, int options,
>    /* Legacy Rust symbols need to be handled separately. */
>    if (rdm.version == -1)
>      {
> -      /* Legacy Rust symbols always end with E. */
> +      /* Legacy Rust symbols always end with E.  But can be followed by a
> +         .suffix (which we want to ignore).  */
> +      int dot_suffix = 1;
> +      while (rdm.sym_len > 0 &&
> +             !(dot_suffix && rdm.sym[rdm.sym_len - 1] == 'E'))
> +        {
> +          dot_suffix = rdm.sym[rdm.sym_len - 1] == '.';
> +          rdm.sym_len--;
> +        }
> +
>        if (!(rdm.sym_len > 0 && rdm.sym[rdm.sym_len - 1] == 'E'))
>          return 0;
>        rdm.sym_len--;
> diff --git a/libiberty/testsuite/rust-demangle-expected b/libiberty/testsuite/rust-demangle-expected
> index 7dca315d0054..b565084cfefa 100644
> --- a/libiberty/testsuite/rust-demangle-expected
> +++ b/libiberty/testsuite/rust-demangle-expected
> @@ -295,3 +295,29 @@ _RMCs4fqI2P2rA04_13const_genericINtB0_4CharKc2202_E
>  --format=auto
>  _RNvNvMCs4fqI2P2rA04_13const_genericINtB4_3FooKpE3foo3FOO
>  <const_generic::Foo<_>>::foo::FOO
> +#
> +# Suffixes
> +#
> +--format=rust
> +_RNvMs0_NtCs5l0EXMQXRMU_21rustc_data_structures17obligation_forestINtB5_16ObligationForestNtNtNtCsdozMG8X9FIu_21rustc_trait_selection6traits7fulfill26PendingPredicateObligationE22register_obligation_atB1v_.llvm.8517020237817239694
> +<rustc_data_structures::obligation_forest::ObligationForest<rustc_trait_selection::traits::fulfill::PendingPredicateObligation>>::register_obligation_at
> +--format=rust
> +_ZN4core3ptr85drop_in_place$LT$std..rt..lang_start$LT$$LP$$RP$$GT$..$u7b$$u7b$closure$u7d$$u7d$$GT$17h27f14859c664490dE.llvm.8091179795805947855
> +core::ptr::drop_in_place<std::rt::lang_start<()>::{{closure}}>
> +# old style rustc llvm thinlto
> +--format=rust
> +_ZN9backtrace3foo17hbb467fcdaea5d79bE.llvm.A5310EB9
> +backtrace::foo
> +--format=rust
> +_ZN9backtrace3foo17hbb467fcdaea5d79bE.llvm.A5310EB9@@16
> +backtrace::foo
> +# new style rustc llvm thinlto
> +--format=rust
> +_RC3foo.llvm.9D1C9369
> +foo
> +--format=rust
> +_RC3foo.llvm.9D1C9369@@16
> +foo
> +--format=rust
> +_RNvC9backtrace3foo.llvm.A5310EB9
> +backtrace::foo
> -- 
> 2.30.2
>