[clang] 37c74df - Revert "[c++17] Implement P0145R3 during constant evaluation."
Dmitri Gribenko via cfe-commits
cfe-commits at lists.llvm.org
Tue Oct 6 06:49:56 PDT 2020
Author: Dmitri Gribenko
Date: 2020-10-06T15:49:44+02:00
New Revision: 37c74dfe72ecf4e7def22702c5a944682a7865df
URL: https://github.com/llvm/llvm-project/commit/37c74dfe72ecf4e7def22702c5a944682a7865df
DIFF: https://github.com/llvm/llvm-project/commit/37c74dfe72ecf4e7def22702c5a944682a7865df.diff
LOG: Revert "[c++17] Implement P0145R3 during constant evaluation."
This reverts commit ded79be63555f4e5bfdb0db27ef22b71fe568474. It causes
a crash (I sent the crash reproducer directly to the author).
Added:
Modified:
clang/lib/AST/ExprConstant.cpp
clang/test/SemaCXX/constant-expression-cxx1z.cpp
clang/www/cxx_status.html
Removed:
################################################################################
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 49ad01f27545..4460e3a17e6d 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -1856,12 +1856,8 @@ void CallStackFrame::describe(raw_ostream &Out) {
Out << ", ";
const ParmVarDecl *Param = *I;
- if (Arguments) {
- const APValue &Arg = Arguments[ArgIndex];
- Arg.printPretty(Out, Info.Ctx, Param->getType());
- } else {
- Out << "<...>";
- }
+ const APValue &Arg = Arguments[ArgIndex];
+ Arg.printPretty(Out, Info.Ctx, Param->getType());
if (ArgIndex == 0 && IsMemberCall)
Out << "->" << *Callee << '(';
@@ -5796,8 +5792,6 @@ typedef SmallVector<APValue, 8> ArgVector;
/// EvaluateArgs - Evaluate the arguments to a function call.
static bool EvaluateArgs(ArrayRef<const Expr *> Args, ArgVector &ArgValues,
EvalInfo &Info, const FunctionDecl *Callee) {
- ArgValues.resize(Args.size());
-
bool Success = true;
llvm::SmallBitVector ForbiddenNullArgs;
if (Callee->hasAttr<NonNullAttr>()) {
@@ -5815,6 +5809,8 @@ static bool EvaluateArgs(ArrayRef<const Expr *> Args, ArgVector &ArgValues,
}
}
}
+ // FIXME: This is the wrong evaluation order for an assignment operator
+ // called via operator syntax.
for (unsigned Idx = 0; Idx < Args.size(); Idx++) {
if (!Evaluate(ArgValues[Idx], Info, Args[Idx])) {
// If we're checking for a potential constant expression, evaluate all
@@ -5838,13 +5834,17 @@ static bool EvaluateArgs(ArrayRef<const Expr *> Args, ArgVector &ArgValues,
/// Evaluate a function call.
static bool HandleFunctionCall(SourceLocation CallLoc,
const FunctionDecl *Callee, const LValue *This,
- ArrayRef<const Expr *> Args, APValue *ArgValues,
- const Stmt *Body, EvalInfo &Info,
- APValue &Result, const LValue *ResultSlot) {
+ ArrayRef<const Expr*> Args, const Stmt *Body,
+ EvalInfo &Info, APValue &Result,
+ const LValue *ResultSlot) {
+ ArgVector ArgValues(Args.size());
+ if (!EvaluateArgs(Args, ArgValues, Info, Callee))
+ return false;
+
if (!Info.CheckCallLimit(CallLoc))
return false;
- CallStackFrame Frame(Info, CallLoc, Callee, This, ArgValues);
+ CallStackFrame Frame(Info, CallLoc, Callee, This, ArgValues.data());
// For a trivial copy or move assignment, perform an APValue copy. This is
// essential for unions, where the operations performed by the assignment
@@ -7293,8 +7293,6 @@ class ExprEvaluatorBase
auto Args = llvm::makeArrayRef(E->getArgs(), E->getNumArgs());
bool HasQualifier = false;
- ArgVector ArgValues;
-
// Extract function decl and 'this' pointer from the callee.
if (CalleeType->isSpecificBuiltinType(BuiltinType::BoundMember)) {
const CXXMethodDecl *Member = nullptr;
@@ -7343,22 +7341,6 @@ class ExprEvaluatorBase
return Error(E);
}
- // For an (overloaded) assignment expression, evaluate the RHS before the
- // LHS.
- auto *OCE = dyn_cast<CXXOperatorCallExpr>(E);
- if (OCE && OCE->isAssignmentOp()) {
- assert(Args.size() == 2 && "wrong number of arguments in assignment");
- if (isa<CXXMethodDecl>(FD)) {
- // Args[0] is the object argument.
- if (!EvaluateArgs({Args[1]}, ArgValues, Info, FD))
- return false;
- } else {
- if (!EvaluateArgs({Args[1], Args[0]}, ArgValues, Info, FD))
- return false;
- std::swap(ArgValues[0], ArgValues[1]);
- }
- }
-
// Overloaded operator calls to member functions are represented as normal
// calls with '*this' as the first argument.
const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD);
@@ -7421,11 +7403,6 @@ class ExprEvaluatorBase
} else
return Error(E);
- // Evaluate the arguments now if we've not already done so.
- if (ArgValues.empty() && !Args.empty() &&
- !EvaluateArgs(Args, ArgValues, Info, FD))
- return false;
-
SmallVector<QualType, 4> CovariantAdjustmentPath;
if (This) {
auto *NamedMember = dyn_cast<CXXMethodDecl>(FD);
@@ -7447,7 +7424,6 @@ class ExprEvaluatorBase
// Destructor calls are
diff erent enough that they have their own codepath.
if (auto *DD = dyn_cast<CXXDestructorDecl>(FD)) {
assert(This && "no 'this' pointer for destructor call");
- assert(ArgValues.empty() && "unexpected destructor arguments");
return HandleDestruction(Info, E, *This,
Info.Ctx.getRecordType(DD->getParent()));
}
@@ -7456,8 +7432,8 @@ class ExprEvaluatorBase
Stmt *Body = FD->getBody(Definition);
if (!CheckConstexprFunction(Info, E->getExprLoc(), FD, Definition, Body) ||
- !HandleFunctionCall(E->getExprLoc(), Definition, This, Args,
- ArgValues.data(), Body, Info, Result, ResultSlot))
+ !HandleFunctionCall(E->getExprLoc(), Definition, This, Args, Body, Info,
+ Result, ResultSlot))
return false;
if (!CovariantAdjustmentPath.empty() &&
@@ -8095,20 +8071,17 @@ bool LValueExprEvaluator::VisitArraySubscriptExpr(const ArraySubscriptExpr *E) {
if (E->getBase()->getType()->isVectorType())
return Error(E);
- APSInt Index;
bool Success = true;
-
- // C++17's rules require us to evaluate the LHS first, regardless of which
- // side is the base.
- for (const Expr *SubExpr : {E->getLHS(), E->getRHS()}) {
- if (SubExpr == E->getBase() ? !evaluatePointer(SubExpr, Result)
- : !EvaluateInteger(SubExpr, Index, Info)) {
- if (!Info.noteFailure())
- return false;
- Success = false;
- }
+ if (!evaluatePointer(E->getBase(), Result)) {
+ if (!Info.noteFailure())
+ return false;
+ Success = false;
}
+ APSInt Index;
+ if (!EvaluateInteger(E->getIdx(), Index, Info))
+ return false;
+
return Success &&
HandleLValueArrayAdjustment(Info, E, Result, E->getType(), Index);
}
@@ -8152,10 +8125,7 @@ bool LValueExprEvaluator::VisitCompoundAssignOperator(
if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
return Error(CAO);
- // C++17 onwards require that we evaluate the RHS first.
APValue RHS;
- if (!Evaluate(RHS, this->Info, CAO->getRHS()))
- return false;
// The overall lvalue result is the result of evaluating the LHS.
if (!this->Visit(CAO->getLHS())) {
@@ -8164,6 +8134,9 @@ bool LValueExprEvaluator::VisitCompoundAssignOperator(
return false;
}
+ if (!Evaluate(RHS, this->Info, CAO->getRHS()))
+ return false;
+
return handleCompoundAssignment(
this->Info, CAO,
Result, CAO->getLHS()->getType(), CAO->getComputationLHSType(),
@@ -8174,10 +8147,7 @@ bool LValueExprEvaluator::VisitBinAssign(const BinaryOperator *E) {
if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
return Error(E);
- // C++17 onwards require that we evaluate the RHS first.
APValue NewVal;
- if (!Evaluate(NewVal, this->Info, E->getRHS()))
- return false;
if (!this->Visit(E->getLHS())) {
if (Info.noteFailure())
@@ -8185,6 +8155,9 @@ bool LValueExprEvaluator::VisitBinAssign(const BinaryOperator *E) {
return false;
}
+ if (!Evaluate(NewVal, this->Info, E->getRHS()))
+ return false;
+
if (Info.getLangOpts().CPlusPlus20 &&
!HandleUnionActiveMemberChange(Info, E->getLHS(), Result))
return false;
@@ -15297,8 +15270,7 @@ bool Expr::isPotentialConstantExpr(const FunctionDecl *FD,
} else {
SourceLocation Loc = FD->getLocation();
HandleFunctionCall(Loc, FD, (MD && MD->isInstance()) ? &This : nullptr,
- Args, /*ArgValues*/ nullptr, FD->getBody(), Info,
- Scratch, nullptr);
+ Args, FD->getBody(), Info, Scratch, nullptr);
}
return Diags.empty();
@@ -15320,8 +15292,13 @@ bool Expr::isPotentialConstantExprUnevaluated(Expr *E,
Info.CheckingPotentialConstantExpression = true;
// Fabricate a call stack frame to give the arguments a plausible cover story.
- CallStackFrame Frame(Info, SourceLocation(), FD, /*This*/ nullptr,
- /*ArgValues*/ nullptr);
+ ArrayRef<const Expr*> Args;
+ ArgVector ArgValues(0);
+ bool Success = EvaluateArgs(Args, ArgValues, Info, FD);
+ (void)Success;
+ assert(Success &&
+ "Failed to set up arguments for potential constant evaluation");
+ CallStackFrame Frame(Info, SourceLocation(), FD, nullptr, ArgValues.data());
APValue ResultScratch;
Evaluate(ResultScratch, Info, E);
diff --git a/clang/test/SemaCXX/constant-expression-cxx1z.cpp b/clang/test/SemaCXX/constant-expression-cxx1z.cpp
index 7770e92c6331..2b366adf2e91 100644
--- a/clang/test/SemaCXX/constant-expression-cxx1z.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx1z.cpp
@@ -59,112 +59,3 @@ void test() {
else if constexpr (v<int>) {}
}
}
-
-// Check that assignment operators evaluate their operands right-to-left.
-namespace EvalOrder {
- template<typename T> struct lvalue {
- T t;
- constexpr T &get() { return t; }
- };
-
- struct UserDefined {
- int n = 0;
- constexpr UserDefined &operator=(const UserDefined&) { return *this; }
- constexpr UserDefined &operator+=(const UserDefined&) { return *this; }
- constexpr void operator<<(const UserDefined&) const {}
- constexpr void operator>>(const UserDefined&) const {}
- constexpr void operator+(const UserDefined&) const {}
- constexpr void operator[](int) const {}
- };
- constexpr UserDefined ud;
-
- struct NonMember {};
- constexpr void operator+=(NonMember, NonMember) {}
- constexpr void operator<<(NonMember, NonMember) {}
- constexpr void operator>>(NonMember, NonMember) {}
- constexpr void operator+(NonMember, NonMember) {}
- constexpr NonMember nm;
-
- constexpr void f(...) {}
-
- // Helper to ensure that 'a' is evaluated before 'b'.
- struct seq_checker {
- bool done_a = false;
- bool done_b = false;
-
- template <typename T> constexpr T &&a(T &&v) {
- done_a = true;
- return (T &&)v;
- }
- template <typename T> constexpr T &&b(T &&v) {
- if (!done_a)
- throw "wrong";
- done_b = true;
- return (T &&)v;
- }
-
- constexpr bool ok() { return done_a && done_b; }
- };
-
- // SEQ(expr), where part of the expression is tagged A(...) and part is
- // tagged B(...), checks that A is evaluated before B.
- #define A sc.a
- #define B sc.b
- #define SEQ(...) static_assert([](seq_checker sc) { void(__VA_ARGS__); return sc.ok(); }({}))
-
- // Longstanding sequencing rules.
- SEQ((A(1), B(2)));
- SEQ((A(true) ? B(2) : throw "huh?"));
- SEQ((A(false) ? throw "huh?" : B(2)));
- SEQ(A(true) && B(true));
- SEQ(A(false) || B(true));
-
- // From P0145R3:
-
- // Rules 1 and 2 have no effect ('b' is not an expression).
-
- // Rule 3: a->*b
- SEQ(A(ud).*B(&UserDefined::n));
- SEQ(A(&ud)->*B(&UserDefined::n));
-
- // Rule 4: a(b1, b2, b3)
- SEQ(A(f)(B(1), B(2), B(3)));
-
- // Rule 5: b = a, b @= a
- SEQ(B(lvalue<int>().get()) = A(0));
- SEQ(B(lvalue<UserDefined>().get()) = A(ud));
- SEQ(B(lvalue<int>().get()) += A(0));
- SEQ(B(lvalue<UserDefined>().get()) += A(ud));
- SEQ(B(lvalue<NonMember>().get()) += A(nm));
-
- // Rule 6: a[b]
- constexpr int arr[3] = {};
- SEQ(A(arr)[B(0)]);
- SEQ(A(+arr)[B(0)]);
- SEQ(A(0)[B(arr)]);
- SEQ(A(0)[B(+arr)]);
- SEQ(A(ud)[B(0)]);
-
- // Rule 7: a << b
- SEQ(A(1) << B(2));
- SEQ(A(ud) << B(ud));
- SEQ(A(nm) << B(nm));
-
- // Rule 8: a >> b
- SEQ(A(1) >> B(2));
- SEQ(A(ud) >> B(ud));
- SEQ(A(nm) >> B(nm));
-
- // No particular order of evaluation is specified in other cases, but we in
- // practice evaluate left-to-right.
- // FIXME: Technically we're expected to check for undefined behavior due to
- // unsequenced read and modification and treat it as non-constant due to UB.
- SEQ(A(1) + B(2));
- SEQ(A(ud) + B(ud));
- SEQ(A(nm) + B(nm));
- SEQ(f(A(1), B(2)));
-
- #undef SEQ
- #undef A
- #undef B
-}
diff --git a/clang/www/cxx_status.html b/clang/www/cxx_status.html
index 9c39e396edd4..3c546eb409de 100755
--- a/clang/www/cxx_status.html
+++ b/clang/www/cxx_status.html
@@ -807,7 +807,6 @@ <h2 id="cxx17">C++17 implementation status</h2>
<tt>operator&&</tt>, <tt>operator||</tt>, and <tt>operator,</tt>
functions using expression syntax are no longer guaranteed to be destroyed in
reverse construction order in that ABI.
-This is not fully supported during constant expression evaluation until Clang 12.
</span><br>
<span id="p0522">(10): Despite being the resolution to a Defect Report, this
feature is disabled by default in all language versions, and can be enabled
More information about the cfe-commits
mailing list