[gcc r13-3167] libiberty: Demangle variadic template lambdas

[gcc r13-3167] libiberty: Demangle variadic template lambdas

[Nathan Sidwell]

https://gcc.gnu.org/g:eb491ea5c10955c667ceeda76dede393c93a377b

commit r13-3167-geb491ea5c10955c667ceeda76dede393c93a377b
Author: Nathan Sidwell <nathan@acm.org>
Date:   Fri Sep 30 12:11:42 2022 -0700

    libiberty: Demangle variadic template lambdas
    
    Now we have templated lambdas, we can have variadic template lambdas,
    and this leads to lambda signatures containing parameter packs.  But
    just like 'auto' inside such a signature, we don't have a containing
    template, and thus fail.  The fix is to check is_lambda_arg, just as
    for a template parameter.  This allows us to demangle g++'s manglings
    of such lambdas.
    
    It's not a totally accurate demangling, because we don't mangle the
    template head (that's a separate issue), but it is better than failing
    to demangle.
    
    Due to the way we print subexprs, we add an unnecessary parens around
    the argument of the pack.  That's an orthogonal problem, for which the
    solution is to have better knowledge of operator precedence.
    
            libiberty/
            * cp-demangle.c (d_print_comp_inner): Allow parameter packs
            in a lambda signature.
            * testsuite/demangle-expected: Add tests.

Diff:
---
 libiberty/cp-demangle.c               | 30 +++++++++++++++++-------------
 libiberty/testsuite/demangle-expected |  7 +++++++
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/libiberty/cp-demangle.c b/libiberty/cp-demangle.c
index 7ff225ec1aa..303bfbf709e 100644
--- a/libiberty/cp-demangle.c
+++ b/libiberty/cp-demangle.c
@@ -348,7 +348,7 @@ struct d_print_info
      be bigger than MAX_RECURSION_COUNT.  */
   int recursion;
   /* Non-zero if we're printing a lambda argument.  A template
-     parameter reference actually means 'auto'.  */
+     parameter reference actually means 'auto', a pack expansion means T...  */
   int is_lambda_arg;
   /* The current index into any template argument packs we are using
      for printing, or -1 to print the whole pack.  */
@@ -5930,9 +5930,10 @@ d_print_comp_inner (struct d_print_info *dpi, int options,
 
     case DEMANGLE_COMPONENT_PACK_EXPANSION:
       {
-	int len;
-	int i;
-	struct demangle_component *a = d_find_pack (dpi, d_left (dc));
+	struct demangle_component *a = NULL;
+
+	if (!dpi->is_lambda_arg)
+	  a = d_find_pack (dpi, d_left (dc));
 	if (a == NULL)
 	  {
 	    /* d_find_pack won't find anything if the only packs involved
@@ -5940,17 +5941,20 @@ d_print_comp_inner (struct d_print_info *dpi, int options,
 	       case, just print the pattern and "...".  */
 	    d_print_subexpr (dpi, options, d_left (dc));
 	    d_append_string (dpi, "...");
-	    return;
 	  }
-
-	len = d_pack_length (a);
-	dc = d_left (dc);
-	for (i = 0; i < len; ++i)
+	else
 	  {
-	    dpi->pack_index = i;
-	    d_print_comp (dpi, options, dc);
-	    if (i < len-1)
-	      d_append_string (dpi, ", ");
+	    int len = d_pack_length (a);
+	    int i;
+
+	    dc = d_left (dc);
+	    for (i = 0; i < len; ++i)
+	      {
+		if (i)
+		  d_append_string (dpi, ", ");
+		dpi->pack_index = i;
+		d_print_comp (dpi, options, dc);
+	      }
 	  }
       }
       return;
diff --git a/libiberty/testsuite/demangle-expected b/libiberty/testsuite/demangle-expected
index 8fad6893ae7..90dd4a13945 100644
--- a/libiberty/testsuite/demangle-expected
+++ b/libiberty/testsuite/demangle-expected
@@ -1574,3 +1574,10 @@ initializer for module Foo.Bar
 
 _ZGIW3FooWP3BarW3Baz
 initializer for module Foo:Bar.Baz
+
+_ZZ2L1vENKUlDpT_E_clIJiPiEEEvS0_
+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
+