[gcc r13-1956] Adjust index number of tuple pretty printer

[Ulrich Drepper <drepper@gcc.gnu.org>]

https://gcc.gnu.org/g:075683767abe15b936ad41792da6ee71e9eda449

commit r13-1956-g075683767abe15b936ad41792da6ee71e9eda449
Author: Ulrich Drepper <drepper@gmail.com>
Date:   Thu Aug 4 13:18:05 2022 +0200

    Adjust index number of tuple pretty printer
    
    The tuple pretty printer uses 1-based indeces which is quite confusing
    considering the access to the same values with the std::get functions
    uses 0-based indeces.  This patch changes the pretty printer since
    this is not a guaranteed API.
    
    libstdc++-v3/ChangeLog:
    
            * python/libstdcxx/v6/printers.py (class StdTuplePrinter): Use
            zero-based indeces just like std:get takes.

Diff:
---
 libstdc++-v3/python/libstdcxx/v6/printers.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/python/libstdcxx/v6/printers.py b/libstdc++-v3/python/libstdcxx/v6/printers.py
index 17c33c1e54f..d70c8d5d616 100644
--- a/libstdc++-v3/python/libstdcxx/v6/printers.py
+++ b/libstdc++-v3/python/libstdcxx/v6/printers.py
@@ -611,9 +611,9 @@ class StdTuplePrinter:
             # the value "as is".
             fields = impl.type.fields ()
             if len (fields) < 1 or fields[0].name != "_M_head_impl":
-                return ('[%d]' % self.count, impl)
+                return ('[%d]' % (self.count - 1), impl)
             else:
-                return ('[%d]' % self.count, impl['_M_head_impl'])
+                return ('[%d]' % (self.count - 1), impl['_M_head_impl'])
 
     def __init__ (self, typename, val):
         self.typename = strip_versioned_namespace(typename)