Make system_error::message() thread safe. Fixes PR25598.

Summary:
system_error::message() uses `strerror` for the generic and system categories. This function is not thread safe.

The fix is to use `strerror_r`. It has been available since 2001 for GNU libc and since BSD 4.4 on FreeBSD/OS X.
On platforms with GNU libc the extended version is used which always returns a valid string, even if an error occurs.

In single-threaded builds `strerror` is still used.

See https://llvm.org/bugs/show_bug.cgi?id=25598

Reviewers: majnemer, mclow.lists

Subscribers: erik65536, cfe-commits, emaste

Differential Revision: http://reviews.llvm.org/D20903

llvm-svn: 272633

2 files changed, 23 insertions, 0 deletions

diff --git a/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/generic_category.pass.cpp b/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/generic_category.pass.cpp
index 972299936dd..7afbbd06980 100644
--- a/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/generic_category.pass.cpp
+++ b/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/generic_category.pass.cpp
@@ -16,10 +16,21 @@
 #include <system_error>
 #include <cassert>
 #include <string>
+#include <cerrno>
+
+void test_message_leaves_errno_unchanged() {
+    errno = E2BIG; // something that message will never generate
+    const std::error_category& e_cat1 = std::generic_category();
+    e_cat1.message(-1);
+    assert(errno == E2BIG);
+}
 
 int main()
 {
     const std::error_category& e_cat1 = std::generic_category();
     std::string m1 = e_cat1.name();
     assert(m1 == "generic");
+    {
+        test_message_leaves_errno_unchanged();
+    }
 }
diff --git a/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/system_category.pass.cpp b/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/system_category.pass.cpp
index b5cb18ad765..8c1e8029252 100644
--- a/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/system_category.pass.cpp
+++ b/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/system_category.pass.cpp
@@ -16,6 +16,15 @@
 #include <system_error>
 #include <cassert>
 #include <string>
+#include <cerrno>
+
+
+void test_message_leaves_errno_unchanged() {
+    errno = E2BIG; // something that message will never generate
+    const std::error_category& e_cat1 = std::system_category();
+    e_cat1.message(-1);
+    assert(errno == E2BIG);
+}
 
 int main()
 {
@@ -26,4 +35,7 @@ int main()
     e_cond = e_cat1.default_error_condition(5000);
     assert(e_cond.value() == 5000);
     assert(e_cond.category() == std::system_category());
+    {
+        test_message_leaves_errno_unchanged();
+    }
 }