[OpenMP] Fix infinite loop in Sema::isOpenMPGlobalCapturedDecl()

[nullptr.cpp]

Summary

Function Sema::isOpenMPGlobalCapturedDecl() has a parameter unsigned Level,
but use Level >= 0 as the condition of while, thus cause an infinite loop.
Fix by changing the loop condition to Level > 0.

[jdoerfert]

Can you add the test that exposed this?

[nullptr.cpp]

Fix by changing the loop condition to Level > 0.

[nullptr.cpp]

In D86858#2246925, @jdoerfert wrote:

Can you add the test that exposed this?

Sorry, this was discovered by a static analyzer checker.

[jdoerfert]

LG, @ABataev ?

[ABataev]

LG

[nullptr.cpp]

trigger rebuild

[nullptr.cpp]

@jdoerfert @ABataev
I don't have commit access, can you help commit this?
Yang Fan <[e-mail]>
Thanks!

clang/lib/Sema/SemaOpenMP.cpp

if (!VD->hasLocalStorage()) {
           getOpenMPCaptureLevels(DSAStack->getDirective(Level));
       if (Level == 0)
         return (NumLevels == CaptureLevel + 1) && TopDVar.CKind != OMPC_shared;
       do {
         --Level;
         DSAStackTy::DSAVarData DVar = DSAStack->getImplicitDSA(D, Level);
         if (DVar.CKind != OMPC_shared)
           return true;
-      } while (Level >= 0);
+      } while (Level > 0);
     }
   }
   return true;
 }
 
 void Sema::DestroyDataSharingAttributesStack() { delete DSAStack; }
 
 void Sema::ActOnOpenMPBeginDeclareVariant(SourceLocation Loc,