[analyzer] Track the problematic subexpression in UndefResultChecker

[george.karpenkov]

Summary

This is be tested in a dependent revision, which allows tracking those values

[NoQ]

Yeah, i guess the checker is responsible for it. The checker just knows what part it wants to track.

clang/lib/StaticAnalyzer/Checkers/UndefResultChecker.cpp

126

Accidental newline.

clang/lib/StaticAnalyzer/Checkers/UndefResultChecker.cpp

if (Ex) {
       // Neither operand was undefined, but the result is undefined.
       if ((B->getOpcode() == BinaryOperatorKind::BO_Shl ||
            B->getOpcode() == BinaryOperatorKind::BO_Shr) &&
           C.isNegative(B->getRHS())) {
         OS << "The result of the "
            << ((B->getOpcode() == BinaryOperatorKind::BO_Shl) ? "left"
                                                               : "right")
            << " shift is undefined because the right operand is negative";
+        Ex = B->getRHS();
+
       } else if ((B->getOpcode() == BinaryOperatorKind::BO_Shl ||
                   B->getOpcode() == BinaryOperatorKind::BO_Shr) &&
                  isShiftOverflow(B, C)) {
 
         OS << "The result of the "
            << ((B->getOpcode() == BinaryOperatorKind::BO_Shl) ? "left"
                                                               : "right")
            << " shift is undefined due to shifting by ";
+        Ex = B->getRHS();
 
         SValBuilder &SB = C.getSValBuilder();
         const llvm::APSInt *I =
             SB.getKnownValue(C.getState(), C.getSVal(B->getRHS()));
         if (!I)
           OS << "a value that is";
         else if (I->isUnsigned())
           OS << '\'' << I->getZExtValue() << "\', which is";
         else
           OS << '\'' << I->getSExtValue() << "\', which is";
 
         OS << " greater or equal to the width of type '"
            << B->getLHS()->getType().getAsString() << "'.";
       } else if (B->getOpcode() == BinaryOperatorKind::BO_Shl &&
                  C.isNegative(B->getLHS())) {
         OS << "The result of the left shift is undefined because the left "
               "operand is negative";
+        Ex = B->getLHS();
       } else if (B->getOpcode() == BinaryOperatorKind::BO_Shl &&
                  isLeftShiftResultUnrepresentable(B, C)) {
         ProgramStateRef State = C.getState();
         SValBuilder &SB = C.getSValBuilder();
         const llvm::APSInt *LHS =
             SB.getKnownValue(State, C.getSVal(B->getLHS()));
         const llvm::APSInt *RHS =
             SB.getKnownValue(State, C.getSVal(B->getRHS()));
         OS << "The result of the left shift is undefined due to shifting \'"
            << LHS->getSExtValue() << "\' by \'" << RHS->getZExtValue()
            << "\', which is unrepresentable in the unsigned version of "
            << "the return type \'" << B->getLHS()->getType().getAsString()
            << "\'";
+        Ex = B->getLHS();
       } else {
         OS << "The result of the '"
            << BinaryOperator::getOpcodeStr(B->getOpcode())
            << "' expression is undefined";
       }
     }
     auto report = llvm::make_unique<BugReport>(*BT, OS.str(), N);
     if (Ex) {