libstdc++: std::system_category should know meaning of zero [PR102425]

Although 0 is not an errno value, it should still be recognized as
corresponding to a value belonging to the generic_category().

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	PR libstdc++/102425
	* src/c++11/system_error.cc
	(system_error_category::default_error_condition): Add 0 to
	switch.
	* testsuite/19_diagnostics/error_category/102425.cc: New test.

1 files changed, 18 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/19_diagnostics/error_category/102425.cc b/libstdc++-v3/testsuite/19_diagnostics/error_category/102425.cc
new file mode 100644
index 00000000000..069b5e284e1
--- /dev/null
+++ b/libstdc++-v3/testsuite/19_diagnostics/error_category/102425.cc
@@ -0,0 +1,18 @@
+// { dg-do run { target c++11 } }
+#include <system_error>
+#include <testsuite_hooks.h>
+
+void test01()
+{
+  // PR libstdc++/102425
+  VERIFY( std::error_code() == std::error_condition() );
+
+  auto zero = std::system_category().default_error_condition(0);
+  // This is the condition that the equality above relies on:
+  VERIFY( zero.category() == std::generic_category() );
+}
+
+int main()
+{
+  test01();
+}