C++ (Cpp) CheckerContext::isGreaterOrEqual Examples

Example #1

File: ConversionChecker.cpp Project: LegalizeAdulthood/clang

bool ConversionChecker::isLossOfPrecision(const ImplicitCastExpr *Cast,
                                          QualType DestType,
                                          CheckerContext &C) const {
  // Don't warn about explicit loss of precision.
  if (Cast->isEvaluatable(C.getASTContext()))
    return false;

  QualType SubType = Cast->IgnoreParenImpCasts()->getType();

  if (!DestType->isRealType() || !SubType->isIntegerType())
    return false;

  const bool isFloat = DestType->isFloatingType();

  const auto &AC = C.getASTContext();

  // We will find the largest RepresentsUntilExp value such that the DestType
  // can exactly represent all nonnegative integers below 2^RepresentsUntilExp.
  unsigned RepresentsUntilExp;

  if (isFloat) {
    const llvm::fltSemantics &Sema = AC.getFloatTypeSemantics(DestType);
    RepresentsUntilExp = llvm::APFloat::semanticsPrecision(Sema);
  } else {
    RepresentsUntilExp = AC.getIntWidth(DestType);
    if (RepresentsUntilExp == 1) {
      // This is just casting a number to bool, probably not a bug.
      return false;
    }
    if (DestType->isSignedIntegerType())
      RepresentsUntilExp--;
  }

  if (RepresentsUntilExp >= sizeof(unsigned long long) * CHAR_BIT) {
    // Avoid overflow in our later calculations.
    return false;
  }

  unsigned CorrectedSrcWidth = AC.getIntWidth(SubType);
  if (SubType->isSignedIntegerType())
    CorrectedSrcWidth--;

  if (RepresentsUntilExp >= CorrectedSrcWidth) {
    // Simple case: the destination can store all values of the source type.
    return false;
  }

  unsigned long long MaxVal = 1ULL << RepresentsUntilExp;
  if (isFloat) {
    // If this is a floating point type, it can also represent MaxVal exactly.
    MaxVal++;
  }
  return C.isGreaterOrEqual(Cast->getSubExpr(), MaxVal);
  // TODO: maybe also check negative values with too large magnitude.
}