libstdc++: Add pretty printer for std::span

This improves the debug output for C++20 spans.

Before:
{static extent = 18446744073709551615, _M_ptr = 0x7fffffffb9a8, _M_extent = {_M_extent_value = 2}}
Now with StdSpanPrinter:
std::span of length 2 = {1, 2}

Signed-off-by: Philipp Fent <fent@in.tum.de>

libstdc++-v3/ChangeLog:

	* python/libstdcxx/v6/printers.py (StdSpanPrinter): Define.
	* testsuite/libstdc++-prettyprinters/cxx20.cc: Test it.

1 files changed, 11 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx20.cc b/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx20.cc
index b0de25c27ec..76023df93fa 100644
--- a/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx20.cc
+++ b/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx20.cc
@@ -18,8 +18,10 @@
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
+#include <array>
 #include <compare>
 #include <iostream>
+#include <span>
 
 struct X
 {
@@ -54,6 +56,15 @@ main()
   auto c10 = 0.0 <=> __builtin_nan("");
 // { dg-final { note-test c10 "std::partial_ordering::unordered" } }
 
+  auto il = {1, 2};
+  auto s1 = std::span(il);
+  static_assert(s1.extent == std::size_t(-1));
+// { dg-final { note-test s1 {std::span of length 2 = {1, 2}} } }
+  auto a = std::array{3, 4};
+  auto s2 = std::span(a);
+  static_assert(s2.extent == std::size_t(2));
+// { dg-final { note-test s2 {std::span of length 2 = {3, 4}} } }
+
   std::cout << "\n";
   return 0;			// Mark SPOT
 }