[gcc r12-7279] libiberty rust-demangle, ignore .suffix

[Mark Wielaard]

https://gcc.gnu.org/g:d3b2ead595467166c849950ecd3710501a5094d9

commit r12-7279-gd3b2ead595467166c849950ecd3710501a5094d9
Author: Mark Wielaard <mark@klomp.org>
Date:   Thu Dec 2 18:00:39 2021 +0100

    libiberty rust-demangle, ignore .suffix
    
    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.

Diff:
---
 libiberty/rust-demangle.c                  | 21 ++++++++++++++++++---
 libiberty/testsuite/rust-demangle-expected | 26 ++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/libiberty/rust-demangle.c b/libiberty/rust-demangle.c
index 3b24d63892a..bb58d900e27 100644
--- a/libiberty/rust-demangle.c
+++ b/libiberty/rust-demangle.c
@@ -1375,13 +1375,19 @@ 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;
@@ -1390,7 +1396,16 @@ 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 7dca315d005..b565084cfef 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