[PATCH] D52888: Thread safety analysis: Handle conditional expression in getTrylockCallExpr

[Aaron Puchert via Phabricator via cfe-commits]

aaronpuchert created this revision.
aaronpuchert added reviewers: aaron.ballman, delesley, hokein.
Herald added a subscriber: cfe-commits.

We unwrap conditional expressions containing try-lock functions.

Additionally we don't branch on conditionals, since that is usually not
helpful. When joining the branches we would almost certainly get a
warning otherwise.

Hopefully fixes an issue that was raised in https://reviews.llvm.org/D52398.


Repository:
  rC Clang

https://reviews.llvm.org/D52888

Files:
  lib/Analysis/ThreadSafety.cpp
  test/SemaCXX/warn-thread-safety-analysis.cpp


Index: test/SemaCXX/warn-thread-safety-analysis.cpp
===================================================================
--- test/SemaCXX/warn-thread-safety-analysis.cpp
+++ test/SemaCXX/warn-thread-safety-analysis.cpp
@@ -1873,6 +1873,23 @@
    int i = a;
    mu.Unlock();
   }
+
+  // Test with conditional operator
+  void foo13() {
+    if (mu.TryLock() ? 1 : 0)
+      mu.Unlock();
+  }
+
+  void foo14() {
+    if (mu.TryLock() ? 0 : 1)
+      return;
+    mu.Unlock();
+  }
+
+  void foo15() {
+    if (mu.TryLock() ? 0 : 1) // expected-note{{mutex acquired here}}
+      mu.Unlock();            // expected-warning{{releasing mutex 'mu' that was not held}}
+  }                           // expected-warning{{mutex 'mu' is not held on every path through here}}
 };  // end TestTrylock
 
 } // end namespace TrylockTest
Index: lib/Analysis/ThreadSafety.cpp
===================================================================
--- lib/Analysis/ThreadSafety.cpp
+++ lib/Analysis/ThreadSafety.cpp
@@ -1435,6 +1435,17 @@
     if (BOP->getOpcode() == BO_LOr)
       return getTrylockCallExpr(BOP->getRHS(), C, Negate);
     return nullptr;
+  } else if (const auto *COP = dyn_cast<ConditionalOperator>(Cond)) {
+    bool TCond, FCond;
+    if (getStaticBooleanValue(COP->getTrueExpr(), TCond) &&
+        getStaticBooleanValue(COP->getFalseExpr(), FCond)) {
+      if (TCond && !FCond)
+        return getTrylockCallExpr(COP->getCond(), C, Negate);
+      if (!TCond && FCond) {
+        Negate = !Negate;
+        return getTrylockCallExpr(COP->getCond(), C, Negate);
+      }
+    }
   }
   return nullptr;
 }
@@ -1449,7 +1460,8 @@
   Result = ExitSet;
 
   const Stmt *Cond = PredBlock->getTerminatorCondition();
-  if (!Cond)
+  // We don't branch on ?:, we branch when the result is used.
+  if (!Cond || isa<ConditionalOperator>(PredBlock->getTerminator()))
     return;
 
   bool Negate = false;


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