[patch] Fix std::try_lock behaviour

[Jonathan Wakely]

When I fixed std::try_lock a few years ago I misread the spec,
exceptions should not be caught and turned into a return value.

Tested x86_64-linux, committed to trunk.


commit 5effca670aa009c60e31b639604da4d00f388038
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Thu Sep 18 16:15:54 2014 +0100

    	* include/std/mutex (try_lock): Do not swallow exceptions.
    	* testsuite/30_threads/try_lock/4.cc: Fix test.

diff --git a/libstdc++-v3/include/std/mutex b/libstdc++-v3/include/std/mutex
index f6b851c..d80fa5a 100644
--- a/libstdc++-v3/include/std/mutex
+++ b/libstdc++-v3/include/std/mutex
@@ -630,12 +630,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       int __idx;
       auto __locks = std::tie(__l1, __l2, __l3...);
-      __try
-      { __try_lock_impl<0>::__do_try_lock(__locks, __idx); }
-      __catch(const __cxxabiv1::__forced_unwind&)
-      { __throw_exception_again; }
-      __catch(...)
-      { }
+      __try_lock_impl<0>::__do_try_lock(__locks, __idx);
       return __idx;
     }
 
diff --git a/libstdc++-v3/testsuite/30_threads/try_lock/4.cc b/libstdc++-v3/testsuite/30_threads/try_lock/4.cc
index 7741798..1212b65 100644
--- a/libstdc++-v3/testsuite/30_threads/try_lock/4.cc
+++ b/libstdc++-v3/testsuite/30_threads/try_lock/4.cc
@@ -133,8 +133,15 @@ void test03()
       while (unreliable_lock::throw_on < 3)
       {
         unreliable_lock::count = 0;
-        int failed = std::try_lock(l1, l2, l3);
-        VERIFY( failed == unreliable_lock::throw_on );
+        try
+          {
+            std::try_lock(l1, l2, l3);
+            VERIFY( false );
+          }
+        catch (int e)
+          {
+            VERIFY( e == unreliable_lock::throw_on );
+          }
         ++unreliable_lock::throw_on;
       }
     }