[analyzer] Make CheckerManager::hasPathSensitiveCheckers() complete again

[steakhal]

Summary

It turns out that the CheckerManager::hasPathSensitiveCheckers() missed checking for the BeginFunctionCheckers.
It seems like other callbacks are also missing:

• ObjCMessageNilCheckers
• BeginFunctionCheckers
• NewAllocatorCheckers
• PointerEscapeCheckers
• EndOfTranslationUnitCheckers

In this patch, I wanted to use a fold-expression, but until C++17 arrives we are left with the old-school method.

When I tried to write a unittest I observed an interesting behavior. I subscribed only to the BeginFunction event, it was not fired.
However, when I also defined the PreCall with an empty handler, suddenly both fired.
I could add this test demonstrating the issue, but I don't think it would serve much value in a long run. I don't expect regressions for this.

However, I think it would be great to enforce the completeness of this list in a runtime check.
I could not come up with a solution for this though.

PS: Thank you @Szelethus for helping me debugging this.

[vsavchenko]

Great! Thanks for the detailed explanation in your Summary.
I agree that there should be a runtime check, but it doesn't seem viable as long as Checker.h is organized the way it is organized now.

clang/lib/StaticAnalyzer/Core/CheckerManager.cpp

40

Maybe we can use LLVM_ATTRIBUTE_UNUSED instead?

clang/lib/StaticAnalyzer/Core/CheckerManager.cpp

 #include "llvm/Support/ErrorHandling.h"
 #include <cassert>
 #include <vector>
 
 using namespace clang;
 using namespace ento;
 
 bool CheckerManager::hasPathSensitiveCheckers() const {
-  return !StmtCheckers.empty()              ||
-         !PreObjCMessageCheckers.empty()    ||
-         !PostObjCMessageCheckers.empty()   ||
-         !PreCallCheckers.empty()    ||
-         !PostCallCheckers.empty()   ||
-         !LocationCheckers.empty()          ||
-         !BindCheckers.empty()              ||
-         !EndAnalysisCheckers.empty()       ||
-         !EndFunctionCheckers.empty()           ||
-         !BranchConditionCheckers.empty()   ||
-         !LiveSymbolsCheckers.empty()       ||
-         !DeadSymbolsCheckers.empty()       ||
-         !RegionChangesCheckers.empty()     ||
-         !EvalAssumeCheckers.empty()        ||
-         !EvalCallCheckers.empty();
+  const auto IfAnyAreNonEmpty = [](const auto &... Callbacks) -> bool {
+    bool Result = false;
+    // FIXME: Use fold expressions in C++17.
+    LLVM_ATTRIBUTE_UNUSED int Unused[]{0, (Result |= !Callbacks.empty())...};
+    return Result;
+  };
+  return IfAnyAreNonEmpty(
+      StmtCheckers, PreObjCMessageCheckers, ObjCMessageNilCheckers,
+      PostObjCMessageCheckers, PreCallCheckers, PostCallCheckers,
+      LocationCheckers, BindCheckers, EndAnalysisCheckers,
+      BeginFunctionCheckers, EndFunctionCheckers, BranchConditionCheckers,
+      NewAllocatorCheckers, LiveSymbolsCheckers, DeadSymbolsCheckers,
+      RegionChangesCheckers, PointerEscapeCheckers, EvalAssumeCheckers,
+      EvalCallCheckers, EndOfTranslationUnitCheckers);
 }
 
 void CheckerManager::finishedCheckerRegistration() {
 #ifndef NDEBUG
   // Make sure that for every event that has listeners, there is at least
   // one dispatcher registered for it.
   for (const auto &Event : Events)
     assert(Event.second.HasDispatcher &&