For P0784R7: compute whether a variable has constant destruction if it
has a constexpr destructor.
For constexpr variables, reject if the variable does not have constant
destruction. In all cases, do not emit runtime calls to the destructor
for variables with constant destruction.
llvm-svn: 373159
diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
index 6b6a8ab..cbac50d 100644
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -808,12 +808,19 @@
/// valid if CheckedICE is true.
bool IsICE : 1;
+ /// Whether this variable is known to have constant destruction. That is,
+ /// whether running the destructor on the initial value is a side-effect
+ /// (and doesn't inspect any state that might have changed during program
+ /// execution). This is currently only computed if the destructor is
+ /// non-trivial.
+ bool HasConstantDestruction : 1;
+
Stmt *Value;
APValue Evaluated;
- EvaluatedStmt() : WasEvaluated(false), IsEvaluating(false), CheckedICE(false),
- CheckingICE(false), IsICE(false) {}
-
+ EvaluatedStmt()
+ : WasEvaluated(false), IsEvaluating(false), CheckedICE(false),
+ CheckingICE(false), IsICE(false), HasConstantDestruction(false) {}
};
/// Represents a variable declaration or definition.
@@ -1267,6 +1274,14 @@
/// to untyped APValue if the value could not be evaluated.
APValue *getEvaluatedValue() const;
+ /// Evaluate the destruction of this variable to determine if it constitutes
+ /// constant destruction.
+ ///
+ /// \pre isInitICE()
+ /// \return \c true if this variable has constant destruction, \c false if
+ /// not.
+ bool evaluateDestruction(SmallVectorImpl<PartialDiagnosticAt> &Notes) const;
+
/// Determines whether it is already known whether the
/// initializer is an integral constant expression or not.
bool isInitKnownICE() const;
@@ -1505,9 +1520,14 @@
// has no definition within this source file.
bool isKnownToBeDefined() const;
- /// Do we need to emit an exit-time destructor for this variable?
+ /// Is destruction of this variable entirely suppressed? If so, the variable
+ /// need not have a usable destructor at all.
bool isNoDestroy(const ASTContext &) const;
+ /// Do we need to emit an exit-time destructor for this variable, and if so,
+ /// what kind?
+ QualType::DestructionKind needsDestruction(const ASTContext &Ctx) const;
+
// Implement isa/cast/dyncast/etc.
static bool classof(const Decl *D) { return classofKind(D->getKind()); }
static bool classofKind(Kind K) { return K >= firstVar && K <= lastVar; }
diff --git a/clang/include/clang/Basic/DiagnosticASTKinds.td b/clang/include/clang/Basic/DiagnosticASTKinds.td
index 7f935d4..eb2a1f0 100644
--- a/clang/include/clang/Basic/DiagnosticASTKinds.td
+++ b/clang/include/clang/Basic/DiagnosticASTKinds.td
@@ -145,8 +145,10 @@
"a constant expression">;
def note_constexpr_volatile_here : Note<
"volatile %select{temporary created|object declared|member declared}0 here">;
-def note_constexpr_ltor_mutable : Note<
- "read of mutable member %0 is not allowed in a constant expression">;
+def note_constexpr_access_mutable : Note<
+ "%select{read of|read of|assignment to|increment of|decrement of|"
+ "member call on|dynamic_cast of|typeid applied to|destruction of}0 "
+ "mutable member %1 is not allowed in a constant expression">;
def note_constexpr_ltor_non_const_int : Note<
"read of non-const variable %0 is not allowed in a constant expression">;
def note_constexpr_ltor_non_constexpr : Note<
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index adc658b..d1b9aea 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2384,6 +2384,8 @@
"constexpr variable cannot have non-literal type %0">;
def err_constexpr_var_requires_const_init : Error<
"constexpr variable %0 must be initialized by a constant expression">;
+def err_constexpr_var_requires_const_destruction : Error<
+ "constexpr variable %0 must have constant destruction">;
def err_constexpr_redecl_mismatch : Error<
"%select{non-constexpr|constexpr|consteval}1 declaration of %0"
" follows %select{non-constexpr|constexpr|consteval}2 declaration">;
