Add more tests for cxa_guard methods. This includes our first two tests using

actual threads!

There's no build file for libcxxabi, so I'll tell you that I built it with this:
$ g++-4.6 -pthread -std=gnu++0x test_guard.cpp ../src/cxa_guard.o -o test_guard

llvm-svn: 132644

libcxxabi/test/test_guard.cpp

@@ -10,7 +10,9 @@
 #include "cxxabi.h"
 
 #include <cassert>
+#include <thread>
 
+// Ensure that we initialize each variable once and only once.
 namespace test1 {
     static int run_count = 0;
     int increment() {
@@ -32,6 +34,8 @@ namespace test1 {
     }
 }
 
+// When initialization fails, ensure that we try to initialize it again next
+// time.
 namespace test2 {
     static int run_count = 0;
     int increment() {
@@ -52,8 +56,79 @@ namespace test2 {
     }
 }
 
+// Check that we can initialize a second value while initializing a first.
+namespace test3 {
+    int zero() {
+        return 0;
+    }
+
+    int one() {
+        static int b = zero();
+        return 0;
+    }
+
+    void test() {
+        static int a = one();
+    }
+}
+
+// A simple thread test of two threads racing to initialize a variable. This
+// isn't guaranteed to catch any particular threading problems.
+namespace test4 {
+    static int run_count = 0;
+    int increment() {
+        ++run_count;
+	return 0;
+    }
+
+    void helper() {
+        static int a = increment();
+    }
+
+    void test() {
+        std::thread t1(helper), t2(helper);
+        t1.join();
+        t2.join();
+	assert(run_count == 1);
+    }
+}
+
+// Check that we don't re-initialize a static variable even when it's
+// encountered from two different threads.
+namespace test5 {
+    static int run_count = 0;
+    int zero() {
+        ++run_count;
+        return 0;
+    }
+
+    int one() {
+        static int b = zero();
+	return 0;
+    }
+
+    void another_helper() {
+        static int a = one();
+    }
+
+    void helper() {
+        static int a = one();
+	std::thread t(another_helper);
+	t.join();
+    }
+
+    void test() {
+        std::thread t(helper);
+        t.join();
+	assert(run_count == 1);
+    }
+}
+
 int main()
 {
     test1::test();
     test2::test();
+    test3::test();
+    test4::test();
+    test5::test();
 }