Author: rsmith
Date: Tue Oct 8 19:04:54 2019
New Revision: 374135
URL: http://llvm.org/viewvc/llvm-project?rev=374135&view=rev
Log:
[c++20] P1152R4: warn on any simple-assignment to a volatile lvalue
whose value is not ignored.
We don't warn on all the cases that are deprecated: specifically, we
choose to not warn for now if there are parentheses around the
assignment but its value is not actually used. This seems like a more
defensible rule, particularly for cases like sizeof(v = a), where the
parens are part of the operand rather than the sizeof syntax.
Modified:
cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
cfe/trunk/include/clang/Sema/Sema.h
cfe/trunk/lib/Sema/SemaExpr.cpp
cfe/trunk/lib/Sema/SemaExprCXX.cpp
cfe/trunk/test/SemaCXX/deprecated.cpp
cfe/trunk/www/cxx_status.html
Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=374135&r1=374134&r2=374135&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Tue Oct 8 19:04:54
2019
@@ -6654,6 +6654,9 @@ def err_increment_decrement_enum : Error
def warn_deprecated_increment_decrement_volatile : Warning<
"%select{decrement|increment}0 of object of volatile-qualified type %1 "
"is deprecated">, InGroup<DeprecatedVolatile>;
+def warn_deprecated_simple_assign_volatile : Warning<
+ "use of result of assignment to object of volatile-qualified type %0 "
+ "is deprecated">, InGroup<DeprecatedVolatile>;
def warn_deprecated_compound_assign_volatile : Warning<
"compound assignment to object of volatile-qualified type %0 is deprecated">,
InGroup<DeprecatedVolatile>;
Modified: cfe/trunk/include/clang/Sema/Sema.h
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/Sema.h?rev=374135&r1=374134&r2=374135&view=diff
==============================================================================
--- cfe/trunk/include/clang/Sema/Sema.h (original)
+++ cfe/trunk/include/clang/Sema/Sema.h Tue Oct 8 19:04:54 2019
@@ -1062,6 +1062,11 @@ public:
llvm::SmallPtrSet<const Expr *, 8> PossibleDerefs;
+ /// Expressions appearing as the LHS of a volatile assignment in this
+ /// context. We produce a warning for these when popping the context if
+ /// they are not discarded-value expressions nor unevaluated operands.
+ SmallVector<Expr*, 2> VolatileAssignmentLHSs;
+
/// \brief Describes whether we are in an expression constext which we have
/// to handle differently.
enum ExpressionKind {
@@ -4248,6 +4253,9 @@ public:
ExprResult TransformToPotentiallyEvaluated(Expr *E);
ExprResult HandleExprEvaluationContextForTypeof(Expr *E);
+ ExprResult CheckUnevaluatedOperand(Expr *E);
+ void CheckUnusedVolatileAssignment(Expr *E);
+
ExprResult ActOnConstantExpression(ExprResult Res);
// Functions for marking a declaration referenced. These functions also
Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=374135&r1=374134&r2=374135&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExpr.cpp Tue Oct 8 19:04:54 2019
@@ -3801,6 +3801,16 @@ bool Sema::CheckUnaryExprOrTypeTraitOper
QualType ExprTy = E->getType();
assert(!ExprTy->isReferenceType());
+ bool IsUnevaluatedOperand =
+ (ExprKind == UETT_SizeOf || ExprKind == UETT_AlignOf ||
+ ExprKind == UETT_PreferredAlignOf);
+ if (IsUnevaluatedOperand) {
+ ExprResult Result = CheckUnevaluatedOperand(E);
+ if (Result.isInvalid())
+ return true;
+ E = Result.get();
+ }
+
if (ExprKind == UETT_VecStep)
return CheckVecStepTraitOperandType(*this, ExprTy, E->getExprLoc(),
E->getSourceRange());
@@ -3838,9 +3848,8 @@ bool Sema::CheckUnaryExprOrTypeTraitOper
// The operand for sizeof and alignof is in an unevaluated expression
context,
// so side effects could result in unintended consequences.
- if ((ExprKind == UETT_SizeOf || ExprKind == UETT_AlignOf ||
- ExprKind == UETT_PreferredAlignOf) &&
- !inTemplateInstantiation() && E->HasSideEffects(Context, false))
+ if (IsUnevaluatedOperand && !inTemplateInstantiation() &&
+ E->HasSideEffects(Context, false))
Diag(E->getExprLoc(), diag::warn_side_effects_unevaluated_context);
if (CheckObjCTraitOperandConstraints(*this, ExprTy, E->getExprLoc(),
@@ -3939,8 +3948,6 @@ bool Sema::CheckUnaryExprOrTypeTraitOper
}
static bool CheckAlignOfExpr(Sema &S, Expr *E, UnaryExprOrTypeTrait ExprKind) {
- E = E->IgnoreParens();
-
// Cannot know anything else if the expression is dependent.
if (E->isTypeDependent())
return false;
@@ -3952,9 +3959,10 @@ static bool CheckAlignOfExpr(Sema &S, Ex
}
ValueDecl *D = nullptr;
- if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
+ Expr *Inner = E->IgnoreParens();
+ if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Inner)) {
D = DRE->getDecl();
- } else if (MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
+ } else if (MemberExpr *ME = dyn_cast<MemberExpr>(Inner)) {
D = ME->getMemberDecl();
}
@@ -11944,7 +11952,7 @@ QualType Sema::CheckAssignmentOperands(E
// A simple-assignment whose left operand is of a volatile-qualified
// type is deprecated unless the assignment is either a discarded-value
// expression or an unevaluated operand
- // FIXME: Implement checks for this.
+ ExprEvalContexts.back().VolatileAssignmentLHSs.push_back(LHSExpr);
} else {
// C++2a [expr.ass]p6:
// [Compound-assignment] expressions are deprecated if E1 has
@@ -15082,6 +15090,26 @@ void Sema::WarnOnPendingNoDerefs(Express
Rec.PossibleDerefs.clear();
}
+/// Check whether E, which is either a discarded-value expression or an
+/// unevaluated operand, is a simple-assignment to a volatlie-qualified lvalue,
+/// and if so, remove it from the list of volatile-qualified assignments that
+/// we are going to warn are deprecated.
+void Sema::CheckUnusedVolatileAssignment(Expr *E) {
+ if (!E->getType().isVolatileQualified() || !getLangOpts().CPlusPlus2a)
+ return;
+
+ // Note: ignoring parens here is not justified by the standard rules, but
+ // ignoring parentheses seems like a more reasonable approach, and this only
+ // drives a deprecation warning so doesn't affect conformance.
+ if (auto *BO = dyn_cast<BinaryOperator>(E->IgnoreParenImpCasts())) {
+ if (BO->getOpcode() == BO_Assign) {
+ auto &LHSs = ExprEvalContexts.back().VolatileAssignmentLHSs;
+ LHSs.erase(std::remove(LHSs.begin(), LHSs.end(), BO->getLHS()),
+ LHSs.end());
+ }
+ }
+}
+
void Sema::PopExpressionEvaluationContext() {
ExpressionEvaluationContextRecord& Rec = ExprEvalContexts.back();
unsigned NumTypos = Rec.NumTypos;
@@ -15116,6 +15144,13 @@ void Sema::PopExpressionEvaluationContex
WarnOnPendingNoDerefs(Rec);
+ // Warn on any volatile-qualified simple-assignments that are not discarded-
+ // value expressions nor unevaluated operands (those cases get removed from
+ // this list by CheckUnusedVolatileAssignment).
+ for (auto *BO : Rec.VolatileAssignmentLHSs)
+ Diag(BO->getBeginLoc(), diag::warn_deprecated_simple_assign_volatile)
+ << BO->getType();
+
// When are coming out of an unevaluated context, clear out any
// temporaries that we may have created as part of the evaluation of
// the expression in that context: they aren't relevant because they
Modified: cfe/trunk/lib/Sema/SemaExprCXX.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExprCXX.cpp?rev=374135&r1=374134&r2=374135&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExprCXX.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExprCXX.cpp Tue Oct 8 19:04:54 2019
@@ -499,6 +499,11 @@ ExprResult Sema::BuildCXXTypeId(QualType
}
}
+ ExprResult Result = CheckUnevaluatedOperand(E);
+ if (Result.isInvalid())
+ return ExprError();
+ E = Result.get();
+
// C++ [expr.typeid]p4:
// [...] If the type of the type-id is a reference to a possibly
// cv-qualified type, the result of the typeid expression refers to a
@@ -6609,6 +6614,11 @@ ExprResult Sema::ActOnDecltypeExpression
ExprEvalContexts.back().ExprContext =
ExpressionEvaluationContextRecord::EK_Other;
+ Result = CheckUnevaluatedOperand(E);
+ if (Result.isInvalid())
+ return ExprError();
+ E = Result.get();
+
// In MS mode, don't perform any extra checking of call return types within a
// decltype expression.
if (getLangOpts().MSVCCompat)
@@ -7233,7 +7243,10 @@ ExprResult Sema::BuildCXXNoexceptExpr(So
if (R.isInvalid())
return R;
- // The operand may have been modified when checking the placeholder type.
+ R = CheckUnevaluatedOperand(R.get());
+ if (R.isInvalid())
+ return ExprError();
+
Operand = R.get();
if (!inTemplateInstantiation() && Operand->HasSideEffects(Context, false)) {
@@ -7337,12 +7350,17 @@ ExprResult Sema::IgnoredValueConversions
// volatile lvalue with a special form, we perform an lvalue-to-rvalue
// conversion.
if (getLangOpts().CPlusPlus11 && E->isGLValue() &&
- E->getType().isVolatileQualified() &&
- IsSpecialDiscardedValue(E)) {
- ExprResult Res = DefaultLvalueConversion(E);
- if (Res.isInvalid())
- return E;
- E = Res.get();
+ E->getType().isVolatileQualified()) {
+ if (IsSpecialDiscardedValue(E)) {
+ ExprResult Res = DefaultLvalueConversion(E);
+ if (Res.isInvalid())
+ return E;
+ E = Res.get();
+ } else {
+ // Per C++2a [expr.ass]p5, a volatile assignment is not deprecated if
+ // it occurs as a discarded-value expression.
+ CheckUnusedVolatileAssignment(E);
+ }
}
// C++1z:
@@ -7377,6 +7395,14 @@ ExprResult Sema::IgnoredValueConversions
return E;
}
+ExprResult Sema::CheckUnevaluatedOperand(Expr *E) {
+ // Per C++2a [expr.ass]p5, a volatile assignment is not deprecated if
+ // it occurs as an unevaluated operand.
+ CheckUnusedVolatileAssignment(E);
+
+ return E;
+}
+
// If we can unambiguously determine whether Var can never be used
// in a constant expression, return true.
// - if the variable and its initializer are non-dependent, then
Modified: cfe/trunk/test/SemaCXX/deprecated.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/deprecated.cpp?rev=374135&r1=374134&r2=374135&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/deprecated.cpp (original)
+++ cfe/trunk/test/SemaCXX/deprecated.cpp Tue Oct 8 19:04:54 2019
@@ -1,13 +1,17 @@
-// RUN: %clang_cc1 -std=c++98 %s -Wdeprecated -verify -triple x86_64-linux-gnu
-// RUN: %clang_cc1 -std=c++11 %s -Wdeprecated -verify -triple x86_64-linux-gnu
-// RUN: %clang_cc1 -std=c++14 %s -Wdeprecated -verify -triple x86_64-linux-gnu
-// RUN: %clang_cc1 -std=c++17 %s -Wdeprecated -verify -triple x86_64-linux-gnu
-// RUN: %clang_cc1 -std=c++2a %s -Wdeprecated -verify=expected,cxx20 -triple
x86_64-linux-gnu
+// RUN: %clang_cc1 -std=c++98 %s -Wno-parentheses -Wdeprecated -verify -triple
x86_64-linux-gnu
+// RUN: %clang_cc1 -std=c++11 %s -Wno-parentheses -Wdeprecated -verify -triple
x86_64-linux-gnu
+// RUN: %clang_cc1 -std=c++14 %s -Wno-parentheses -Wdeprecated -verify -triple
x86_64-linux-gnu
+// RUN: %clang_cc1 -std=c++17 %s -Wno-parentheses -Wdeprecated -verify -triple
x86_64-linux-gnu
+// RUN: %clang_cc1 -std=c++2a %s -Wno-parentheses -Wdeprecated
-verify=expected,cxx20 -triple x86_64-linux-gnu
-// RUN: %clang_cc1 -std=c++14 %s -Wdeprecated -verify -triple x86_64-linux-gnu
-Wno-deprecated-register -DNO_DEPRECATED_FLAGS
+// RUN: %clang_cc1 -std=c++14 %s -Wno-parentheses -Wdeprecated -verify -triple
x86_64-linux-gnu -Wno-deprecated-register -DNO_DEPRECATED_FLAGS
#include "Inputs/register.h"
+namespace std {
+ struct type_info {};
+}
+
void g() throw();
void h() throw(int);
void i() throw(...);
@@ -133,17 +137,36 @@ namespace DeprecatedVolatile {
n = 5; // ok
#if __cplusplus >= 201103L
decltype(n = 5) m = n; // ok expected-warning {{side effects}}
- m = sizeof(n = 5); // ok expected-warning {{side effects}}
+ (void)noexcept(n = 5); // ok expected-warning {{side effects}}
#endif
+ (void)typeid(n = 5); // ok expected-warning {{side effects}}
(n = 5, 0); // ok
- use(n = 5); // FIXME: deprecated
- (n = 5); // FIXME: deprecated
- int q = n = 5; // FIXME: deprecated
- q = n = 5; // FIXME: deprecated
+ use(n = 5); // cxx20-warning {{use of result of assignment to object of
volatile-qualified type 'volatile int' is deprecated}}
+ int q = n = 5; // cxx20-warning {{deprecated}}
+ q = n = 5; // cxx20-warning {{deprecated}}
#if __cplusplus >= 201103L
- decltype(q = n = 5) m2 = q; // FIXME: deprecated expected-warning {{side
effects}}
+ decltype(q = n = 5) m2 = q; // cxx20-warning {{deprecated}}
expected-warning {{side effects}}
+ (void)noexcept(q = n = 5); // cxx20-warning {{deprecated}}
expected-warning {{side effects}}
#endif
- q = sizeof(q = n = 5); // FIXME: deprecated expected-warning {{side
effects}}
+ (void)sizeof(q = n = 5); // cxx20-warning {{deprecated}} expected-warning
{{side effects}}
+ (void)typeid(use(n = 5)); // cxx20-warning {{deprecated}} expected-warning
{{side effects}}
+ (void)__alignof(+(n = 5)); // cxx20-warning {{deprecated}}
expected-warning {{side effects}}
+
+ // FIXME: These cases are technically deprecated because the parens are
+ // part of the operand, but we choose to not diagnose for now.
+ (void)sizeof(n = 5); // expected-warning {{side effects}}
+ (void)__alignof(n = 5); // expected-warning {{side effects}}
+ // Similarly here.
+ (n = 5);
+
+ volatile bool b = true;
+ if (b = true) {} // cxx20-warning {{deprecated}}
+ for (b = true;
+ b = true; // cxx20-warning {{deprecated}}
+ b = true) {}
+ for (volatile bool x = true;
+ volatile bool y = true; // ok despite volatile load from volatile
initialization
+ ) {}
// inc / dec / compound assignments are always deprecated
++n; // cxx20-warning {{increment of object of volatile-qualified type
'volatile int' is deprecated}}
Modified: cfe/trunk/www/cxx_status.html
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/www/cxx_status.html?rev=374135&r1=374134&r2=374135&view=diff
==============================================================================
--- cfe/trunk/www/cxx_status.html (original)
+++ cfe/trunk/www/cxx_status.html Tue Oct 8 19:04:54 2019
@@ -1103,7 +1103,7 @@ as the draft C++2a standard evolves.
<tr>
<td>Deprecate some problematic uses of <tt>volatile</tt></td>
<td><a href="http://wg21.link/p1152r4";>P1152R4</a></td>
- <td class="partial" align="center">Partial</td>
+ <td class="svn" align="center">SVN</td>
</tr>
<tr>
<td><tt>[[nodiscard("with reason")]]</tt></td>
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