[PATCH 2/4] libstdc++: Improve output of default contract violation handler [PR107792]

[Arsen Arsenović]

From: Jonathan Wakely <jwakely@redhat.com>

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

libstdc++-v3/ChangeLog:

	PR libstdc++/107792
	PR libstdc++/107778
	* src/experimental/contract.cc (handle_contract_violation): Make
	output more readable.
---
 libstdc++-v3/src/experimental/contract.cc | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/libstdc++-v3/src/experimental/contract.cc b/libstdc++-v3/src/experimental/contract.cc
index c8d2697eddc..6a7f064d35e 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 +24,21 @@
 // <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()
+#if _GLIBCXX_HOSTED && _GLIBCXX_VERBOSE
+  const char* modes[]{ "never", "maybe" }; // Must match enumerators in header.
+  std::cerr << "contract violation in function " << violation.function_name()
+    << " at " << violation.file_name() << ':' << violation.line_number()
+    << ": " << violation.comment()
+    << "\n[level:" << violation.assertion_level()
+    << ", role:" << violation.assertion_role() << ", continuation mode:"
+    << modes[(int)violation.continuation_mode()] << ']'
     << std::endl;
+#endif
 }
-
-- 
2.38.1