tuple pretty printer

tuple pretty printer

[Ulrich Drepper]

The current tuple pretty printer shows for this variable

std::tuple<int,int,int> a{1,2,3};

the following output:

(gdb) p a
$1 = std::tuple containing = {[1] = 1, [2] = 2, [3] = 3}

I find this quite irritating because the indices don't match the
std::get template parameters.  In a large tuple or arrays of tuples
which are less readable than this simple example this becomes an even
larger problem.  How about the following simple patch which brings the
indices in line?

--- 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)

Re: tuple pretty printer

[Jonathan Wakely]

CC gcc-patches

On Wed, 27 Jul 2022 at 17:40, Ulrich Drepper via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> The current tuple pretty printer shows for this variable
>
> std::tuple<int,int,int> a{1,2,3};
>
> the following output:
>
> (gdb) p a
> $1 = std::tuple containing = {[1] = 1, [2] = 2, [3] = 3}
>
> I find this quite irritating because the indices don't match the
> std::get template parameters.  In a large tuple or arrays of tuples
> which are less readable than this simple example this becomes an even
> larger problem.  How about the following simple patch which brings the
> indices in line?

I think this makes sense, want to push it?


>
> --- 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)
>