[PATCH] libstdc++: Define pretty printer for comparison categories

[Jonathan Wakely]

        * python/libstdcxx/v6/printers.py (StdCmpCatPrinter): New printer.
        * testsuite/libstdc++-prettyprinters/cxx20.cc: New test.

Tested x86_64-linux, committed to trunk.

commit b41a87d7889f2399d4c1a0c626a656ba384e71a8
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Thu Dec 5 00:24:58 2019 +0000

    libstdc++: Define pretty printer for comparison categories
    
            * python/libstdcxx/v6/printers.py (StdCmpCatPrinter): New printer.
            * testsuite/libstdc++-prettyprinters/cxx20.cc: New test.

diff --git a/libstdc++-v3/python/libstdcxx/v6/printers.py 
b/libstdc++-v3/python/libstdcxx/v6/printers.py
index 869a8286675..5eab57ea6a7 100644
--- a/libstdc++-v3/python/libstdcxx/v6/printers.py
+++ b/libstdc++-v3/python/libstdcxx/v6/printers.py
@@ -1425,6 +1425,20 @@ class StdPairPrinter:
     def to_string(self):
         return None
 
+class StdCmpCatPrinter:
+    "Print a comparison category object"
+
+    def __init__ (self, typename, val):
+        self.typename = typename[typename.rfind(':')+1:]
+        self.val = val['_M_value']
+
+    def to_string (self):
+        if self.typename == 'strong_ordering' and self.val == 0:
+            name = 'equal'
+        else:
+            names = {-127:'unordered', -1:'less', 0:'equivalent', 1:'greater'}
+            name = names[int(self.val)]
+        return 'std::{}::{}'.format(self.typename, name)
 
 # A "regular expression" printer which conforms to the
 # "SubPrettyPrinter" protocol from gdb.printing.
@@ -1928,6 +1942,11 @@ def build_libstdcxx_dictionary ():
     libstdcxx_printer.add_version('std::',
                                   '_Node_handle', StdNodeHandlePrinter)
 
+    # C++20 components
+    libstdcxx_printer.add_version('std::', 'partial_ordering', 
StdCmpCatPrinter)
+    libstdcxx_printer.add_version('std::', 'weak_ordering', StdCmpCatPrinter)
+    libstdcxx_printer.add_version('std::', 'strong_ordering', StdCmpCatPrinter)
+
     # Extensions.
     libstdcxx_printer.add_version('__gnu_cxx::', 'slist', StdSlistPrinter)
 
diff --git a/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx20.cc 
b/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx20.cc
new file mode 100644
index 00000000000..0a3be53f5f4
--- /dev/null
+++ b/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx20.cc
@@ -0,0 +1,61 @@
+// { dg-options "-g -O0 -std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+// Copyright (C) 2014-2019 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <compare>
+#include <iostream>
+
+struct X
+{
+  int i;
+
+  std::weak_ordering operator<=>(X x) const noexcept { return i <=> x.i; }
+};
+
+int
+main()
+{
+  auto c1 = 1 <=> 1;
+// { dg-final { note-test c1 "std::strong_ordering::equal" } }
+  auto c2 = 1 <=> 2;
+// { dg-final { note-test c2 "std::strong_ordering::less" } }
+  auto c3 = 4 <=> 3;
+// { dg-final { note-test c3 "std::strong_ordering::greater" } }
+
+  auto c4 = X{1} <=> X{1};
+// { dg-final { note-test c4 "std::weak_ordering::equivalent" } }
+  auto c5 = X{2} <=> X{3};
+// { dg-final { note-test c5 "std::weak_ordering::less" } }
+  auto c6 = X{2} <=> X{1};
+// { dg-final { note-test c6 "std::weak_ordering::greater" } }
+
+  auto c7 = 0.2 <=> 0.2;
+// { dg-final { note-test c7 "std::partial_ordering::equivalent" } }
+  auto c8 = 2.5 <=> 5.5;
+// { dg-final { note-test c8 "std::partial_ordering::less" } }
+  auto c9 = 7.5 <=> -2.2;
+// { dg-final { note-test c9 "std::partial_ordering::greater" } }
+  auto c10 = 0.0 <=> __builtin_nan("");
+// { dg-final { note-test c10 "std::partial_ordering::unordered" } }
+
+  std::cout << "\n";
+  return 0;                    // Mark SPOT
+}
+
+// { dg-final { gdb-test SPOT } }