[gcc r12-3264] libstdc++: Remove redundant noexcept-specifier on definitions

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:f63e86f797d82772c62a7475dbc6e881727b666f

commit r12-3264-gf63e86f797d82772c62a7475dbc6e881727b666f
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Aug 31 16:30:01 2021 +0100

    libstdc++: Remove redundant noexcept-specifier on definitions
    
    These destructors are noexcept anyway. I removed the redundant noexcept
    from the error_category destructor's declaration in r0-123475, but
    didn't remove it from the defaulted definition in system_error.cc. That
    causes warnings if the library is built with Clang.
    
    This removes the redundant noexcept from ~error_category and
    ~system_error and adds tests to ensure they really are noexcept.
    
    Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
    
    libstdc++-v3/ChangeLog:
    
            * src/c++11/system_error.cc (error_category::~error_category()):
            Remove noexcept-specifier.
            (system_error::~system_error()): Likewise.
            * testsuite/19_diagnostics/error_category/noexcept.cc: New test.
            * testsuite/19_diagnostics/system_error/noexcept.cc: New test.

Diff:
---
 libstdc++-v3/src/c++11/system_error.cc                      |  4 ++--
 .../testsuite/19_diagnostics/error_category/noexcept.cc     | 13 +++++++++++++
 .../testsuite/19_diagnostics/system_error/noexcept.cc       |  6 ++++++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/src/c++11/system_error.cc b/libstdc++-v3/src/c++11/system_error.cc
index 23fb6182825..f12290adaee 100644
--- a/libstdc++-v3/src/c++11/system_error.cc
+++ b/libstdc++-v3/src/c++11/system_error.cc
@@ -338,7 +338,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     _GLIBCXX_THROW_OR_ABORT(system_error(error_code(__i, generic_category())));
   }
 
-  error_category::~error_category() noexcept = default;
+  error_category::~error_category() = default;
 
   const error_category&
   _V2::system_category() noexcept { return system_category_instance; }
@@ -346,7 +346,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   const error_category&
   _V2::generic_category() noexcept { return generic_category_instance; }
 
-  system_error::~system_error() noexcept = default;
+  system_error::~system_error() = default;
 
   error_condition
   error_category::default_error_condition(int __i) const noexcept
diff --git a/libstdc++-v3/testsuite/19_diagnostics/error_category/noexcept.cc b/libstdc++-v3/testsuite/19_diagnostics/error_category/noexcept.cc
new file mode 100644
index 00000000000..210344c7607
--- /dev/null
+++ b/libstdc++-v3/testsuite/19_diagnostics/error_category/noexcept.cc
@@ -0,0 +1,13 @@
+// { dg-do compile { target c++11 } }
+#include <system_error>
+
+extern const std::error_category& cat;
+
+static_assert(std::is_nothrow_destructible<std::error_category>::value, "");
+static_assert(noexcept(cat.name()), "");
+static_assert(noexcept(cat.default_error_condition(1)), "");
+static_assert(noexcept(cat.equivalent(1, {})), "");
+static_assert(noexcept(cat.equivalent({}, 1)), "");
+static_assert(noexcept(cat == cat), "");
+static_assert(noexcept(cat != cat), "");
+static_assert(noexcept(cat < cat), "");
diff --git a/libstdc++-v3/testsuite/19_diagnostics/system_error/noexcept.cc b/libstdc++-v3/testsuite/19_diagnostics/system_error/noexcept.cc
new file mode 100644
index 00000000000..853b7f922b6
--- /dev/null
+++ b/libstdc++-v3/testsuite/19_diagnostics/system_error/noexcept.cc
@@ -0,0 +1,6 @@
+// { dg-do compile { target c++11 } }
+#include <system_error>
+
+static_assert(std::is_nothrow_destructible<std::system_error>::value, "");
+static_assert(noexcept(std::declval<const std::system_error&>().code()), "");
+static_assert(noexcept(std::declval<const std::system_error&>().what()), "");