[-Wunreachable-code] Tweak heuristic for configuration values to include arithmetic operations involving sizeof(), but not raw integers.
This case was motivated by a false positive with the llvm::AlignOf<> specialization in LLVM. llvm-svn: 203363
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@ -189,7 +189,8 @@ static bool isExpandedFromConfigurationMacro(const Stmt *S) {
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/// "sometimes unreachable" code. Such code is usually not interesting
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/// to report as unreachable, and may mask truly unreachable code within
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/// those blocks.
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static bool isConfigurationValue(const Stmt *S) {
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static bool isConfigurationValue(const Stmt *S,
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bool IncludeIntegers = true) {
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if (!S)
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return false;
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@ -201,7 +202,7 @@ static bool isConfigurationValue(const Stmt *S) {
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const DeclRefExpr *DR = cast<DeclRefExpr>(S);
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const ValueDecl *D = DR->getDecl();
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if (const EnumConstantDecl *ED = dyn_cast<EnumConstantDecl>(D))
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return ED ? isConfigurationValue(ED->getInitExpr()) : false;
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return isConfigurationValue(ED->getInitExpr());
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if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
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// As a heuristic, treat globals as configuration values. Note
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// that we only will get here if Sema evaluated this
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@ -215,14 +216,18 @@ static bool isConfigurationValue(const Stmt *S) {
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return false;
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}
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case Stmt::IntegerLiteralClass:
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return isExpandedFromConfigurationMacro(S);
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return IncludeIntegers ? isExpandedFromConfigurationMacro(S)
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: false;
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case Stmt::UnaryExprOrTypeTraitExprClass:
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return true;
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case Stmt::BinaryOperatorClass: {
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const BinaryOperator *B = cast<BinaryOperator>(S);
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return (B->isLogicalOp() || B->isComparisonOp()) &&
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(isConfigurationValue(B->getLHS()) ||
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isConfigurationValue(B->getRHS()));
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// Only include raw integers (not enums) as configuration
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// values if they are used in a logical or comparison operator
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// (not arithmetic).
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IncludeIntegers &= (B->isLogicalOp() || B->isComparisonOp());
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return isConfigurationValue(B->getLHS(), IncludeIntegers) ||
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isConfigurationValue(B->getRHS(), IncludeIntegers);
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}
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case Stmt::UnaryOperatorClass: {
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const UnaryOperator *UO = cast<UnaryOperator>(S);
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@ -175,3 +175,27 @@ void raze(const A& x);
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void test_with_unreachable_tmp_dtors(int x) {
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raze(x ? A() : A()); // no-warning
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}
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// Test sizeof - sizeof in enum declaration.
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enum { BrownCow = sizeof(long) - sizeof(char) };
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enum { CowBrown = 8 - 1 };
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int test_enum_sizeof_arithmetic() {
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if (BrownCow)
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return 1;
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return 2;
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}
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int test_enum_arithmetic() {
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if (CowBrown)
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return 1;
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return 2; // expected-warning {{never be executed}}
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}
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int test_arithmetic() {
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if (8 -1)
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return 1;
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return 2; // expected-warning {{never be executed}}
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}
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