[clang] perform semantic checking in constant context
Summary:
Since the addition of __builtin_is_constant_evaluated the result of an expression can change based on whether it is evaluated in constant context. a lot of semantic checking performs evaluations with out specifying context. which can lead to wrong diagnostics.
for example:
```
constexpr int i0 = (long long)__builtin_is_constant_evaluated() * (1ll << 33); //#1
constexpr int i1 = (long long)!__builtin_is_constant_evaluated() * (1ll << 33); //#2
```
before the patch, #2 was diagnosed incorrectly and #1 wasn't diagnosed.
after the patch #1 is diagnosed as it should and #2 isn't.
Changes:
- add a flag to Sema to passe in constant context mode.
- in SemaChecking.cpp calls to Expr::Evaluate* are now done in constant context when they should.
- in SemaChecking.cpp diagnostics for UB are not checked for in constant context because an error will be emitted by the constant evaluator.
- in SemaChecking.cpp diagnostics for construct that cannot appear in constant context are not checked for in constant context.
- in SemaChecking.cpp diagnostics on constant expression are always emitted because constant expression are always evaluated.
- semantic checking for initialization of constexpr variables is now done in constant context.
- adapt test that were depending on warning changes.
- add test.
Reviewers: rsmith
Reviewed By: rsmith
Subscribers: cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D62009
llvm-svn: 363488
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index 077bb0a..d7a05e7 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -158,6 +158,7 @@
ThreadSafetyDeclCache(nullptr), VarDataSharingAttributesStack(nullptr),
CurScope(nullptr), Ident_super(nullptr), Ident___float128(nullptr) {
TUScope = nullptr;
+ isConstantEvaluatedOverride = false;
LoadedExternalKnownNamespaces = false;
for (unsigned I = 0; I != NSAPI::NumNSNumberLiteralMethods; ++I)
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index b3e8ae1..e8bcc83 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -84,6 +84,7 @@
#include "llvm/Support/Format.h"
#include "llvm/Support/Locale.h"
#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/SaveAndRestore.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
@@ -307,7 +308,8 @@
// - Analyze the format string of sprintf to see how much of buffer is used.
// - Evaluate strlen of strcpy arguments, use as object size.
- if (TheCall->isValueDependent() || TheCall->isTypeDependent())
+ if (TheCall->isValueDependent() || TheCall->isTypeDependent() ||
+ isConstantEvaluated())
return;
unsigned BuiltinID = FD->getBuiltinID(/*ConsiderWrappers=*/true);
@@ -4059,7 +4061,8 @@
SourceLocation CallSiteLoc) {
if (CheckNonNullExpr(S, ArgExpr))
S.DiagRuntimeBehavior(CallSiteLoc, ArgExpr,
- S.PDiag(diag::warn_null_arg) << ArgExpr->getSourceRange());
+ S.PDiag(diag::warn_null_arg)
+ << ArgExpr->getSourceRange());
}
bool Sema::GetFormatNSStringIdx(const FormatAttr *Format, unsigned &Idx) {
@@ -4129,6 +4132,9 @@
SourceLocation CallSiteLoc) {
assert((FDecl || Proto) && "Need a function declaration or prototype");
+ // Already checked by by constant evaluator.
+ if (S.isConstantEvaluated())
+ return;
// Check the attributes attached to the method/function itself.
llvm::SmallBitVector NonNullArgs;
if (FDecl) {
@@ -6059,6 +6065,8 @@
/// TheCall is a constant expression in the range [Low, High].
bool Sema::SemaBuiltinConstantArgRange(CallExpr *TheCall, int ArgNum,
int Low, int High, bool RangeIsError) {
+ if (isConstantEvaluated())
+ return false;
llvm::APSInt Result;
// We can't check the value of a dependent argument.
@@ -6565,6 +6573,8 @@
llvm::SmallBitVector &CheckedVarArgs,
UncoveredArgHandler &UncoveredArg,
llvm::APSInt Offset) {
+ if (S.isConstantEvaluated())
+ return SLCT_NotALiteral;
tryAgain:
assert(Offset.isSigned() && "invalid offset");
@@ -6594,7 +6604,8 @@
bool CheckLeft = true, CheckRight = true;
bool Cond;
- if (C->getCond()->EvaluateAsBooleanCondition(Cond, S.getASTContext())) {
+ if (C->getCond()->EvaluateAsBooleanCondition(Cond, S.getASTContext(),
+ S.isConstantEvaluated())) {
if (Cond)
CheckRight = false;
else
@@ -6795,8 +6806,10 @@
if (BinOp->isAdditiveOp()) {
Expr::EvalResult LResult, RResult;
- bool LIsInt = BinOp->getLHS()->EvaluateAsInt(LResult, S.Context);
- bool RIsInt = BinOp->getRHS()->EvaluateAsInt(RResult, S.Context);
+ bool LIsInt = BinOp->getLHS()->EvaluateAsInt(
+ LResult, S.Context, Expr::SE_NoSideEffects, S.isConstantEvaluated());
+ bool RIsInt = BinOp->getRHS()->EvaluateAsInt(
+ RResult, S.Context, Expr::SE_NoSideEffects, S.isConstantEvaluated());
if (LIsInt != RIsInt) {
BinaryOperatorKind BinOpKind = BinOp->getOpcode();
@@ -6822,7 +6835,9 @@
auto ASE = dyn_cast<ArraySubscriptExpr>(UnaOp->getSubExpr());
if (UnaOp->getOpcode() == UO_AddrOf && ASE) {
Expr::EvalResult IndexResult;
- if (ASE->getRHS()->EvaluateAsInt(IndexResult, S.Context)) {
+ if (ASE->getRHS()->EvaluateAsInt(IndexResult, S.Context,
+ Expr::SE_NoSideEffects,
+ S.isConstantEvaluated())) {
sumOffsets(Offset, IndexResult.Val.getInt(), BO_Add,
/*RHS is int*/ true);
E = ASE->getBase();
@@ -9902,12 +9917,13 @@
/// range of values it might take.
///
/// \param MaxWidth - the width to which the value will be truncated
-static IntRange GetExprRange(ASTContext &C, const Expr *E, unsigned MaxWidth) {
+static IntRange GetExprRange(ASTContext &C, const Expr *E, unsigned MaxWidth,
+ bool InConstantContext) {
E = E->IgnoreParens();
// Try a full evaluation first.
Expr::EvalResult result;
- if (E->EvaluateAsRValue(result, C))
+ if (E->EvaluateAsRValue(result, C, InConstantContext))
return GetValueRange(C, result.Val, GetExprType(E), MaxWidth);
// I think we only want to look through implicit casts here; if the
@@ -9915,7 +9931,7 @@
// being of the new, wider type.
if (const auto *CE = dyn_cast<ImplicitCastExpr>(E)) {
if (CE->getCastKind() == CK_NoOp || CE->getCastKind() == CK_LValueToRValue)
- return GetExprRange(C, CE->getSubExpr(), MaxWidth);
+ return GetExprRange(C, CE->getSubExpr(), MaxWidth, InConstantContext);
IntRange OutputTypeRange = IntRange::forValueOfType(C, GetExprType(CE));
@@ -9926,9 +9942,9 @@
if (!isIntegerCast)
return OutputTypeRange;
- IntRange SubRange
- = GetExprRange(C, CE->getSubExpr(),
- std::min(MaxWidth, OutputTypeRange.Width));
+ IntRange SubRange = GetExprRange(C, CE->getSubExpr(),
+ std::min(MaxWidth, OutputTypeRange.Width),
+ InConstantContext);
// Bail out if the subexpr's range is as wide as the cast type.
if (SubRange.Width >= OutputTypeRange.Width)
@@ -9944,13 +9960,15 @@
// If we can fold the condition, just take that operand.
bool CondResult;
if (CO->getCond()->EvaluateAsBooleanCondition(CondResult, C))
- return GetExprRange(C, CondResult ? CO->getTrueExpr()
- : CO->getFalseExpr(),
- MaxWidth);
+ return GetExprRange(C,
+ CondResult ? CO->getTrueExpr() : CO->getFalseExpr(),
+ MaxWidth, InConstantContext);
// Otherwise, conservatively merge.
- IntRange L = GetExprRange(C, CO->getTrueExpr(), MaxWidth);
- IntRange R = GetExprRange(C, CO->getFalseExpr(), MaxWidth);
+ IntRange L =
+ GetExprRange(C, CO->getTrueExpr(), MaxWidth, InConstantContext);
+ IntRange R =
+ GetExprRange(C, CO->getFalseExpr(), MaxWidth, InConstantContext);
return IntRange::join(L, R);
}
@@ -9986,7 +10004,7 @@
// been coerced to the LHS type.
case BO_Assign:
// TODO: bitfields?
- return GetExprRange(C, BO->getRHS(), MaxWidth);
+ return GetExprRange(C, BO->getRHS(), MaxWidth, InConstantContext);
// Operations with opaque sources are black-listed.
case BO_PtrMemD:
@@ -9996,8 +10014,9 @@
// Bitwise-and uses the *infinum* of the two source ranges.
case BO_And:
case BO_AndAssign:
- return IntRange::meet(GetExprRange(C, BO->getLHS(), MaxWidth),
- GetExprRange(C, BO->getRHS(), MaxWidth));
+ return IntRange::meet(
+ GetExprRange(C, BO->getLHS(), MaxWidth, InConstantContext),
+ GetExprRange(C, BO->getRHS(), MaxWidth, InConstantContext));
// Left shift gets black-listed based on a judgement call.
case BO_Shl:
@@ -10018,7 +10037,7 @@
// Right shift by a constant can narrow its left argument.
case BO_Shr:
case BO_ShrAssign: {
- IntRange L = GetExprRange(C, BO->getLHS(), MaxWidth);
+ IntRange L = GetExprRange(C, BO->getLHS(), MaxWidth, InConstantContext);
// If the shift amount is a positive constant, drop the width by
// that much.
@@ -10037,7 +10056,7 @@
// Comma acts as its right operand.
case BO_Comma:
- return GetExprRange(C, BO->getRHS(), MaxWidth);
+ return GetExprRange(C, BO->getRHS(), MaxWidth, InConstantContext);
// Black-list pointer subtractions.
case BO_Sub:
@@ -10050,7 +10069,7 @@
case BO_Div: {
// Don't 'pre-truncate' the operands.
unsigned opWidth = C.getIntWidth(GetExprType(E));
- IntRange L = GetExprRange(C, BO->getLHS(), opWidth);
+ IntRange L = GetExprRange(C, BO->getLHS(), opWidth, InConstantContext);
// If the divisor is constant, use that.
llvm::APSInt divisor;
@@ -10064,7 +10083,7 @@
}
// Otherwise, just use the LHS's width.
- IntRange R = GetExprRange(C, BO->getRHS(), opWidth);
+ IntRange R = GetExprRange(C, BO->getRHS(), opWidth, InConstantContext);
return IntRange(L.Width, L.NonNegative && R.NonNegative);
}
@@ -10073,8 +10092,8 @@
case BO_Rem: {
// Don't 'pre-truncate' the operands.
unsigned opWidth = C.getIntWidth(GetExprType(E));
- IntRange L = GetExprRange(C, BO->getLHS(), opWidth);
- IntRange R = GetExprRange(C, BO->getRHS(), opWidth);
+ IntRange L = GetExprRange(C, BO->getLHS(), opWidth, InConstantContext);
+ IntRange R = GetExprRange(C, BO->getRHS(), opWidth, InConstantContext);
IntRange meet = IntRange::meet(L, R);
meet.Width = std::min(meet.Width, MaxWidth);
@@ -10091,8 +10110,8 @@
// The default case is to treat the operation as if it were closed
// on the narrowest type that encompasses both operands.
- IntRange L = GetExprRange(C, BO->getLHS(), MaxWidth);
- IntRange R = GetExprRange(C, BO->getRHS(), MaxWidth);
+ IntRange L = GetExprRange(C, BO->getLHS(), MaxWidth, InConstantContext);
+ IntRange R = GetExprRange(C, BO->getRHS(), MaxWidth, InConstantContext);
return IntRange::join(L, R);
}
@@ -10108,12 +10127,12 @@
return IntRange::forValueOfType(C, GetExprType(E));
default:
- return GetExprRange(C, UO->getSubExpr(), MaxWidth);
+ return GetExprRange(C, UO->getSubExpr(), MaxWidth, InConstantContext);
}
}
if (const auto *OVE = dyn_cast<OpaqueValueExpr>(E))
- return GetExprRange(C, OVE->getSourceExpr(), MaxWidth);
+ return GetExprRange(C, OVE->getSourceExpr(), MaxWidth, InConstantContext);
if (const auto *BitField = E->getSourceBitField())
return IntRange(BitField->getBitWidthValue(C),
@@ -10122,8 +10141,9 @@
return IntRange::forValueOfType(C, GetExprType(E));
}
-static IntRange GetExprRange(ASTContext &C, const Expr *E) {
- return GetExprRange(C, E, C.getIntWidth(GetExprType(E)));
+static IntRange GetExprRange(ASTContext &C, const Expr *E,
+ bool InConstantContext) {
+ return GetExprRange(C, E, C.getIntWidth(GetExprType(E)), InConstantContext);
}
/// Checks whether the given value, which currently has the given
@@ -10411,13 +10431,14 @@
// cases involving boolean values for historical reasons. We should pick a
// consistent way of presenting these diagnostics.
if (!InRange || Other->isKnownToHaveBooleanValue()) {
+
S.DiagRuntimeBehavior(
- E->getOperatorLoc(), E,
- S.PDiag(!InRange ? diag::warn_out_of_range_compare
- : diag::warn_tautological_bool_compare)
- << OS.str() << classifyConstantValue(Constant)
- << OtherT << OtherIsBooleanDespiteType << *Result
- << E->getLHS()->getSourceRange() << E->getRHS()->getSourceRange());
+ E->getOperatorLoc(), E,
+ S.PDiag(!InRange ? diag::warn_out_of_range_compare
+ : diag::warn_tautological_bool_compare)
+ << OS.str() << classifyConstantValue(Constant) << OtherT
+ << OtherIsBooleanDespiteType << *Result
+ << E->getLHS()->getSourceRange() << E->getRHS()->getSourceRange());
} else {
unsigned Diag = (isKnownToHaveUnsignedValue(OriginalOther) && Value == 0)
? (HasEnumType(OriginalOther)
@@ -10521,7 +10542,8 @@
}
// Otherwise, calculate the effective range of the signed operand.
- IntRange signedRange = GetExprRange(S.Context, signedOperand);
+ IntRange signedRange =
+ GetExprRange(S.Context, signedOperand, S.isConstantEvaluated());
// Go ahead and analyze implicit conversions in the operands. Note
// that we skip the implicit conversions on both sides.
@@ -10538,7 +10560,8 @@
// change the result of the comparison.
if (E->isEqualityOp()) {
unsigned comparisonWidth = S.Context.getIntWidth(T);
- IntRange unsignedRange = GetExprRange(S.Context, unsignedOperand);
+ IntRange unsignedRange =
+ GetExprRange(S.Context, unsignedOperand, S.isConstantEvaluated());
// We should never be unable to prove that the unsigned operand is
// non-negative.
@@ -10549,9 +10572,9 @@
}
S.DiagRuntimeBehavior(E->getOperatorLoc(), E,
- S.PDiag(diag::warn_mixed_sign_comparison)
- << LHS->getType() << RHS->getType()
- << LHS->getSourceRange() << RHS->getSourceRange());
+ S.PDiag(diag::warn_mixed_sign_comparison)
+ << LHS->getType() << RHS->getType()
+ << LHS->getSourceRange() << RHS->getSourceRange());
}
/// Analyzes an attempt to assign the given value to a bitfield.
@@ -10719,8 +10742,8 @@
if (pruneControlFlow) {
S.DiagRuntimeBehavior(E->getExprLoc(), E,
S.PDiag(diag)
- << SourceType << T << E->getSourceRange()
- << SourceRange(CContext));
+ << SourceType << T << E->getSourceRange()
+ << SourceRange(CContext));
return;
}
S.Diag(E->getExprLoc(), diag)
@@ -11255,8 +11278,8 @@
if (Source->isFixedPointType()) {
if (Target->isUnsaturatedFixedPointType()) {
Expr::EvalResult Result;
- if (E->EvaluateAsFixedPoint(Result, S.Context,
- Expr::SE_AllowSideEffects)) {
+ if (E->EvaluateAsFixedPoint(Result, S.Context, Expr::SE_AllowSideEffects,
+ S.isConstantEvaluated())) {
APFixedPoint Value = Result.Val.getFixedPoint();
APFixedPoint MaxVal = S.Context.getFixedPointMax(T);
APFixedPoint MinVal = S.Context.getFixedPointMin(T);
@@ -11271,7 +11294,8 @@
}
} else if (Target->isIntegerType()) {
Expr::EvalResult Result;
- if (E->EvaluateAsFixedPoint(Result, S.Context,
+ if (!S.isConstantEvaluated() &&
+ E->EvaluateAsFixedPoint(Result, S.Context,
Expr::SE_AllowSideEffects)) {
APFixedPoint FXResult = Result.Val.getFixedPoint();
@@ -11293,7 +11317,8 @@
} else if (Target->isUnsaturatedFixedPointType()) {
if (Source->isIntegerType()) {
Expr::EvalResult Result;
- if (E->EvaluateAsInt(Result, S.Context, Expr::SE_AllowSideEffects)) {
+ if (!S.isConstantEvaluated() &&
+ E->EvaluateAsInt(Result, S.Context, Expr::SE_AllowSideEffects)) {
llvm::APSInt Value = Result.Val.getInt();
bool Overflowed;
@@ -11324,14 +11349,15 @@
if (Target->isSpecificBuiltinType(BuiltinType::Bool))
return;
- IntRange SourceRange = GetExprRange(S.Context, E);
+ IntRange SourceRange = GetExprRange(S.Context, E, S.isConstantEvaluated());
IntRange TargetRange = IntRange::forTargetOfCanonicalType(S.Context, Target);
if (SourceRange.Width > TargetRange.Width) {
// If the source is a constant, use a default-on diagnostic.
// TODO: this should happen for bitfield stores, too.
Expr::EvalResult Result;
- if (E->EvaluateAsInt(Result, S.Context, Expr::SE_AllowSideEffects)) {
+ if (E->EvaluateAsInt(Result, S.Context, Expr::SE_AllowSideEffects,
+ S.isConstantEvaluated())) {
llvm::APSInt Value(32);
Value = Result.Val.getInt();
@@ -11341,11 +11367,11 @@
std::string PrettySourceValue = Value.toString(10);
std::string PrettyTargetValue = PrettyPrintInRange(Value, TargetRange);
- S.DiagRuntimeBehavior(E->getExprLoc(), E,
- S.PDiag(diag::warn_impcast_integer_precision_constant)
- << PrettySourceValue << PrettyTargetValue
- << E->getType() << T << E->getSourceRange()
- << clang::SourceRange(CC));
+ S.DiagRuntimeBehavior(
+ E->getExprLoc(), E,
+ S.PDiag(diag::warn_impcast_integer_precision_constant)
+ << PrettySourceValue << PrettyTargetValue << E->getType() << T
+ << E->getSourceRange() << clang::SourceRange(CC));
return;
}
@@ -12093,7 +12119,8 @@
bool evaluate(const Expr *E, bool &Result) {
if (!EvalOK || E->isValueDependent())
return false;
- EvalOK = E->EvaluateAsBooleanCondition(Result, Self.SemaRef.Context);
+ EvalOK = E->EvaluateAsBooleanCondition(
+ Result, Self.SemaRef.Context, Self.SemaRef.isConstantEvaluated());
return EvalOK;
}
@@ -12446,6 +12473,8 @@
void Sema::CheckCompletedExpr(Expr *E, SourceLocation CheckLoc,
bool IsConstexpr) {
+ llvm::SaveAndRestore<bool> ConstantContext(
+ isConstantEvaluatedOverride, IsConstexpr || isa<ConstantExpr>(E));
CheckImplicitConversions(E, CheckLoc);
if (!E->isInstantiationDependent())
CheckUnsequencedOperations(E);
@@ -12684,6 +12713,10 @@
void Sema::CheckArrayAccess(const Expr *BaseExpr, const Expr *IndexExpr,
const ArraySubscriptExpr *ASE,
bool AllowOnePastEnd, bool IndexNegated) {
+ // Already diagnosed by the constant evaluator.
+ if (isConstantEvaluated())
+ return;
+
IndexExpr = IndexExpr->IgnoreParenImpCasts();
if (IndexExpr->isValueDependent())
return;
@@ -13821,8 +13854,13 @@
/// \param VD Declaration of an identifier that appears in a type tag.
///
/// \param MagicValue Type tag magic value.
+///
+/// \param isConstantEvaluated wether the evalaution should be performed in
+
+/// constant context.
static bool FindTypeTagExpr(const Expr *TypeExpr, const ASTContext &Ctx,
- const ValueDecl **VD, uint64_t *MagicValue) {
+ const ValueDecl **VD, uint64_t *MagicValue,
+ bool isConstantEvaluated) {
while(true) {
if (!TypeExpr)
return false;
@@ -13860,7 +13898,8 @@
const AbstractConditionalOperator *ACO =
cast<AbstractConditionalOperator>(TypeExpr);
bool Result;
- if (ACO->getCond()->EvaluateAsBooleanCondition(Result, Ctx)) {
+ if (ACO->getCond()->EvaluateAsBooleanCondition(Result, Ctx,
+ isConstantEvaluated)) {
if (Result)
TypeExpr = ACO->getTrueExpr();
else
@@ -13896,14 +13935,17 @@
///
/// \param TypeInfo Information about the corresponding C type.
///
+/// \param isConstantEvaluated wether the evalaution should be performed in
+/// constant context.
+///
/// \returns true if the corresponding C type was found.
static bool GetMatchingCType(
- const IdentifierInfo *ArgumentKind,
- const Expr *TypeExpr, const ASTContext &Ctx,
- const llvm::DenseMap<Sema::TypeTagMagicValue,
- Sema::TypeTagData> *MagicValues,
- bool &FoundWrongKind,
- Sema::TypeTagData &TypeInfo) {
+ const IdentifierInfo *ArgumentKind, const Expr *TypeExpr,
+ const ASTContext &Ctx,
+ const llvm::DenseMap<Sema::TypeTagMagicValue, Sema::TypeTagData>
+ *MagicValues,
+ bool &FoundWrongKind, Sema::TypeTagData &TypeInfo,
+ bool isConstantEvaluated) {
FoundWrongKind = false;
// Variable declaration that has type_tag_for_datatype attribute.
@@ -13911,7 +13953,7 @@
uint64_t MagicValue;
- if (!FindTypeTagExpr(TypeExpr, Ctx, &VD, &MagicValue))
+ if (!FindTypeTagExpr(TypeExpr, Ctx, &VD, &MagicValue, isConstantEvaluated))
return false;
if (VD) {
@@ -13989,8 +14031,8 @@
bool FoundWrongKind;
TypeTagData TypeInfo;
if (!GetMatchingCType(ArgumentKind, TypeTagExpr, Context,
- TypeTagForDatatypeMagicValues.get(),
- FoundWrongKind, TypeInfo)) {
+ TypeTagForDatatypeMagicValues.get(), FoundWrongKind,
+ TypeInfo, isConstantEvaluated())) {
if (FoundWrongKind)
Diag(TypeTagExpr->getExprLoc(),
diag::warn_type_tag_for_datatype_wrong_kind)