[gcc r13-3227] libiberty: Demangling 'M' prefixes

[Nathan Sidwell <nathan@gcc.gnu.org>]

https://gcc.gnu.org/g:0fa35c7e2974a22b2107fa378895c3069fe07ff3

commit r13-3227-g0fa35c7e2974a22b2107fa378895c3069fe07ff3
Author: Nathan Sidwell <nathan@acm.org>
Date:   Fri Sep 30 09:43:30 2022 -0700

    libiberty: Demangling 'M' prefixes
    
    The grammar for a lambda context can include <source-name> 'M', and we
    were adding the component that generated to the substitution table
    twice.  Just ignore the 'M' completely -- we'll already have done the
    checks we need when we saw its predecessor.  A prefix cannot be the
    last component of a nested name, so we do not need to check for that
    case (although we could if we wanted to be more lenient).
    
            libiberty/
            * cp-demangle.c (d_prefix): 'M' components are not
            (re-)added to the substitution table.
            * testsuite/demangle-expected: Add tests.

Diff:
---
 libiberty/cp-demangle.c               |  8 +++-----
 libiberty/testsuite/demangle-expected | 21 +++++++++++++++++++++
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/libiberty/cp-demangle.c b/libiberty/cp-demangle.c
index 303bfbf709e..4beb4d257bb 100644
--- a/libiberty/cp-demangle.c
+++ b/libiberty/cp-demangle.c
@@ -1609,12 +1609,10 @@ d_prefix (struct d_info *di, int substable)
 	}
       else if (peek == 'M')
 	{
-	  /* Initializer scope for a lambda.  We don't need to represent
-	     this; the normal code will just treat the variable as a type
-	     scope, which gives appropriate output.  */
-	  if (ret == NULL)
-	    return NULL;
+	  /* Initializer scope for a lambda.  We already added it as a
+  	     substitution candidate, don't do that again.  */
 	  d_advance (di, 1);
+	  continue;
 	}
       else
 	{
diff --git a/libiberty/testsuite/demangle-expected b/libiberty/testsuite/demangle-expected
index 90dd4a13945..bd92b12076b 100644
--- a/libiberty/testsuite/demangle-expected
+++ b/libiberty/testsuite/demangle-expected
@@ -1581,3 +1581,24 @@ void L1()::{lambda((auto:1)...)#1}::operator()<int, int*>(int, int*) const
 _ZZ2L1vENKUlDpT_E_clIJiPiEEEDaS0_
 auto L1()::{lambda((auto:1)...)#1}::operator()<int, int*>(int, int*) const
 
+_Z7captureIN4gvarMUlvE_EE7WrapperIT_EOS3_
+Wrapper<gvar::{lambda()#1}> capture<gvar::{lambda()#1}>(gvar::{lambda()#1}&&)
+
+_ZNK2L2MUlT_T0_E_clIifEEvS_S0_
+void L2::{lambda(auto:1, auto:2)#1}::operator()<int, float>(L2, int) const
+
+_ZNK1C1fMUlT_E_clIMS_iEEDaS1_
+auto C::f::{lambda(auto:1)#1}::operator()<int C::*>(int C::*) const
+
+_ZNK2L2MUlT_T0_E_clIifEEvS0_S1_
+void L2::{lambda(auto:1, auto:2)#1}::operator()<int, float>(int, float) const
+
+_ZNK1B2L3MUlT_T0_E_clIjdEEvS1_S2_
+void B::L3::{lambda(auto:1, auto:2)#1}::operator()<unsigned int, double>(unsigned int, double) const
+
+_Z3fooIN1qMUlvE_ENS0_UlvE0_EEiOT_OT0_
+int foo<q::{lambda()#1}, q::{lambda()#2}>(q::{lambda()#1}&&, q::{lambda()#2}&&)
+
+_ZNK2L1MUlDpT_E_clIJiPiEEEvS1_
+void L1::{lambda((auto:1)...)#1}::operator()<int, int*>(int, int*) const
+