[analyzer] Fix GCDAntipatternChecker to only fire when the semaphore is initialized to zero

Initializing a semaphore with a different constant most likely signals a different intent

rdar://41802552

Differential Revision: https://reviews.llvm.org/D48911

llvm-svn: 337212

2 files changed, 13 insertions, 1 deletions

diff --git a/clang/lib/StaticAnalyzer/Checkers/GCDAntipatternChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/GCDAntipatternChecker.cpp
index 1b7ea53aeac..5cb51b01f04 100644
--- a/clang/lib/StaticAnalyzer/Checkers/GCDAntipatternChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/GCDAntipatternChecker.cpp
@@ -93,7 +93,9 @@ static bool isTest(const Decl *D) {
 static auto findGCDAntiPatternWithSemaphore() -> decltype(compoundStmt()) {
 
   const char *SemaphoreBinding = "semaphore_name";
-  auto SemaphoreCreateM = callExpr(callsName("dispatch_semaphore_create"));
+  auto SemaphoreCreateM = callExpr(allOf(
+      callsName("dispatch_semaphore_create"),
+      hasArgument(0, ignoringParenCasts(integerLiteral(equals(0))))));
 
   auto SemaphoreBindingM = anyOf(
       forEachDescendant(
diff --git a/clang/test/Analysis/gcdantipatternchecker_test.m b/clang/test/Analysis/gcdantipatternchecker_test.m
index adc7a52bf53..24ffe8975dd 100644
--- a/clang/test/Analysis/gcdantipatternchecker_test.m
+++ b/clang/test/Analysis/gcdantipatternchecker_test.m
@@ -333,3 +333,13 @@ void dispatch_group_and_semaphore_use(MyInterface1 *M) {
   }];
   dispatch_semaphore_wait(sema1, 100); // expected-warning{{Waiting on a callback using a semaphore}}
 }
+
+void no_warn_on_nonzero_semaphore(MyInterface1 *M) {
+  dispatch_semaphore_t sema1 = dispatch_semaphore_create(1);
+
+  [M acceptBlock:^{
+      dispatch_semaphore_signal(sema1);
+  }];
+  dispatch_semaphore_wait(sema1, 100); // no-warning
+}
+