[thread-safety][c++] Model std::unique_lock::owns_lock

Summary:
Code often uses std::unique_lock::owns_lock to test if a deferred lock
using the 2-arg std::unique_lock constructor actually acquired the
lock.

Reviewed By: sblackshear

Differential Revision: D6181631

fbshipit-source-id: 11e9df2

infer/src/concurrency/RacerD.ml

@@ -87,6 +87,10 @@ module TransferFunctions (CFG : ProcCfg.S) = struct
       in
       fun pname ->
         QualifiedCppName.Match.match_qualifiers matcher (Typ.Procname.get_qualifiers pname)
+    and is_cpp_trylock =
+      let matcher = QualifiedCppName.Match.of_fuzzy_qual_names ["std::unique_lock::owns_lock"] in
+      fun pname ->
+        QualifiedCppName.Match.match_qualifiers matcher (Typ.Procname.get_qualifiers pname)
     in
     fun pname actuals ->
       match pname with
@@ -121,6 +125,8 @@ module TransferFunctions (CFG : ProcCfg.S) = struct
           Lock
       | Typ.Procname.ObjC_Cpp _ as pname when is_cpp_unlock pname ->
           Unlock
+      | Typ.Procname.ObjC_Cpp _ as pname when is_cpp_trylock pname ->
+          LockedIfTrue
       | pname when Typ.Procname.equal pname BuiltinDecl.__set_locked_attribute ->
           Lock
       | pname when Typ.Procname.equal pname BuiltinDecl.__delete_locked_attribute ->

infer/tests/codetoanalyze/cpp/racerd/issues.exp

@@ -12,3 +12,4 @@ codetoanalyze/cpp/racerd/unique_lock.cpp, basics::UniqueLock_get2, 3, LOCK_CONSI
 codetoanalyze/cpp/racerd/unique_lock.cpp, basics::UniqueLock_get2, 4, LOCK_CONSISTENCY_VIOLATION, [<Read trace>,access to `&this.suspiciously_written2`,<Write trace>,access to `&this.suspiciously_written2`]
 codetoanalyze/cpp/racerd/unique_lock.cpp, basics::UniqueLock_get4, 1, LOCK_CONSISTENCY_VIOLATION, [<Read trace>,access to `&this.suspiciously_read1`,<Write trace>,access to `&this.suspiciously_read1`]
 codetoanalyze/cpp/racerd/unique_lock.cpp, basics::UniqueLock_get4, 2, LOCK_CONSISTENCY_VIOLATION, [<Read trace>,access to `&this.suspiciously_read2`,<Write trace>,access to `&this.suspiciously_read2`]
+codetoanalyze/cpp/racerd/unique_lock.cpp, basics::UniqueLock_get5, 5, LOCK_CONSISTENCY_VIOLATION, [<Read trace>,access to `&this.suspiciously_read1`,<Write trace>,access to `&this.suspiciously_read1`]

infer/tests/codetoanalyze/cpp/racerd/unique_lock.cpp

@@ -58,6 +58,15 @@ class UniqueLock {
     return result + suspiciously_read2;
   }
 
+  int get5() {
+    std::unique_lock<std::mutex> lock(mutex_, std::try_to_lock);
+    if (lock.owns_lock()) {
+      return well_guarded1;
+    } else {
+      return suspiciously_read1;
+    }
+  }
+
  private:
   int well_guarded1;
   int suspiciously_read1;