libstdc++: Improve output of default contract violation handler [PR107792]

Make the output more readable. Don't output anything unless verbose
termination is enabled at configure-time.

The testsuite change was almost entirely mechanical.  Save for two files
which had very short matches, these changes were produced by two seds and a
Perl script, for the more involved cases.  The latter will be added in a
subsequent commit.  The former are as follows:

    sed -E -i "/dg-output/s/default std::handle_contract_violation called: \
    (\S+) (\S+) (\S+(<[A-Za-z0-9, ]*)?>?)\
    /contract violation in function \3 at \1:\2: /" *.C
    sed -i '/dg-output/s/  */ /g'

Whichever files remained failing after the above changes were checked-out,
re-ran, with output extracted, and ran through dg-out-generator.pl.

Co-Authored-By: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	PR libstdc++/107792
	PR libstdc++/107778
	* src/experimental/contract.cc (handle_contract_violation): Make
	output more readable.

gcc/testsuite/ChangeLog:

	* g++.dg/contracts/contracts-access1.C: Convert to new default
	violation handler.
	* g++.dg/contracts/contracts-assume2.C: Ditto.
	* g++.dg/contracts/contracts-config1.C: Ditto.
	* g++.dg/contracts/contracts-constexpr1.C: Ditto.
	* g++.dg/contracts/contracts-ctor-dtor1.C: Ditto.
	* g++.dg/contracts/contracts-deduced2.C: Ditto.
	* g++.dg/contracts/contracts-friend1.C: Ditto.
	* g++.dg/contracts/contracts-multiline1.C: Ditto.
	* g++.dg/contracts/contracts-post3.C: Ditto.
	* g++.dg/contracts/contracts-pre10.C: Ditto.
	* g++.dg/contracts/contracts-pre2.C: Ditto.
	* g++.dg/contracts/contracts-pre2a2.C: Ditto.
	* g++.dg/contracts/contracts-pre3.C: Ditto.
	* g++.dg/contracts/contracts-pre4.C: Ditto.
	* g++.dg/contracts/contracts-pre5.C: Ditto.
	* g++.dg/contracts/contracts-pre7.C: Ditto.
	* g++.dg/contracts/contracts-pre9.C: Ditto.
	* g++.dg/contracts/contracts-redecl3.C: Ditto.
	* g++.dg/contracts/contracts-redecl4.C: Ditto.
	* g++.dg/contracts/contracts-redecl6.C: Ditto.
	* g++.dg/contracts/contracts-redecl7.C: Ditto.
	* g++.dg/contracts/contracts-tmpl-spec1.C: Ditto.
	* g++.dg/contracts/contracts-tmpl-spec2.C: Ditto.
	* g++.dg/contracts/contracts-tmpl-spec3.C: Ditto.
	* g++.dg/contracts/contracts10.C: Ditto.
	* g++.dg/contracts/contracts14.C: Ditto.
	* g++.dg/contracts/contracts15.C: Ditto.
	* g++.dg/contracts/contracts16.C: Ditto.
	* g++.dg/contracts/contracts17.C: Ditto.
	* g++.dg/contracts/contracts19.C: Ditto.
	* g++.dg/contracts/contracts25.C: Ditto.
	* g++.dg/contracts/contracts3.C: Ditto.
	* g++.dg/contracts/contracts35.C: Ditto.
	* g++.dg/contracts/contracts5.C: Ditto.
	* g++.dg/contracts/contracts7.C: Ditto.
	* g++.dg/contracts/contracts9.C: Ditto.

1 files changed, 39 insertions, 11 deletions

diff --git a/libstdc++-v3/src/experimental/contract.cc b/libstdc++-v3/src/experimental/contract.cc
index c8d2697..2d41a63 100644
--- a/libstdc++-v3/src/experimental/contract.cc
+++ b/libstdc++-v3/src/experimental/contract.cc
@@ -1,4 +1,5 @@
 // -*- C++ -*- std::experimental::contract_violation and friends
+
 // Copyright (C) 2019-2022 Free Software Foundation, Inc.
 //
 // This file is part of GCC.
@@ -23,19 +24,46 @@
 // <http://www.gnu.org/licenses/>.
 
 #include <experimental/contract>
-#include <iostream>
+#if _GLIBCXX_HOSTED && _GLIBCXX_VERBOSE
+# include <iostream>
+#endif
 
 __attribute__ ((weak)) void
 handle_contract_violation (const std::experimental::contract_violation &violation)
 {
-  std::cerr << "default std::handle_contract_violation called: \n"
-    << " " << violation.file_name()
-    << " " << violation.line_number()
-    << " " << violation.function_name()
-    << " " << violation.comment()
-    << " " << violation.assertion_level()
-    << " " << violation.assertion_role()
-    << " " << (int)violation.continuation_mode()
-    << std::endl;
-}
+#if _GLIBCXX_HOSTED && _GLIBCXX_VERBOSE
+  bool level_default_p = violation.assertion_level() == "default";
+  bool role_default_p = violation.assertion_role() == "default";
+  bool cont_mode_default_p = violation.continuation_mode()
+    == std::experimental::contract_violation_continuation_mode::never_continue;
+
+  const char* modes[]{ "off", "on" }; // Must match enumerators in header.
+  std::cerr << "contract violation in function " << violation.function_name()
+    << " at " << violation.file_name() << ':' << violation.line_number()
+    << ": " << violation.comment();
+
+  const char* delimiter = "\n[";
 
+  if (!level_default_p)
+    {
+      std::cerr << delimiter << "level:" << violation.assertion_level();
+      delimiter = ", ";
+    }
+  if (!role_default_p)
+    {
+      std::cerr << delimiter << "role:" << violation.assertion_role();
+      delimiter = ", ";
+    }
+  if (!cont_mode_default_p)
+    {
+      std::cerr << delimiter << "continue:"
+		<< modes[(int)violation.continuation_mode() & 1];
+      delimiter = ", ";
+    }
+
+  if (delimiter[0] == ',')
+    std::cerr << ']';
+
+  std::cerr << std::endl;
+#endif
+}