[tsan] Avoid calling Block_copy in the "sync" GCD interceptors

The synchronous dispatch functions in GCD (dispatch_sync, dispatch_barrier_sync), don't make a copy of the passed block. To maintain binary compatibility, we should avoid doing that as well in TSan, as there's no reason to do that. The synchronous dispatch functions will not return before the block is actually executed.

rdar://problem/42242579

Differential Revision: https://reviews.llvm.org/D50920



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@340342 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 34 insertions, 0 deletions

diff --git a/test/tsan/Darwin/gcd-sync-block-copy.mm b/test/tsan/Darwin/gcd-sync-block-copy.mm
new file mode 100644
index 000000000..87658d7f3
--- /dev/null
+++ b/test/tsan/Darwin/gcd-sync-block-copy.mm
@@ -0,0 +1,34 @@
+// This test verifies that dispatch_sync() doesn't actually copy the block under TSan (without TSan, it doesn't).
+
+// RUN: %clang_tsan -fno-sanitize=thread %s -o %t_no_tsan -framework Foundation
+// RUN: %run %t_no_tsan 2>&1 | FileCheck %s
+
+// RUN: %clang_tsan %s -o %t_with_tsan -framework Foundation
+// RUN: %run %t_with_tsan 2>&1 | FileCheck %s
+
+#import <Foundation/Foundation.h>
+
+@interface MyClass : NSObject
+@end
+
+@implementation MyClass
+- (instancetype)retain {
+  // Copying the dispatch_sync'd block below will increment the retain count of
+  // this object. Abort if that happens.
+  abort();
+}
+@end
+
+int main(int argc, const char* argv[]) {
+  dispatch_queue_t q = dispatch_queue_create("my.queue", NULL);
+  id object = [[MyClass alloc] init];
+  dispatch_sync(q, ^{
+    NSLog(@"%@", object);
+  });
+  [object release];
+  NSLog(@"Done.");
+  return 0;
+}
+
+// CHECK: Done.
+// CHECK-NOT: WARNING: ThreadSanitizer