Commit 311f725d authored by Timm Bäder's avatar Timm Bäder
Browse files

[clang][Interp] Create only globals when initializing a global variable 

For this code:

struct O {
  int &&j;
};

O o1(0);

The generated AST for the initializer of o1 is:

VarDecl 0x62100006ab08 <array.cpp:119:3, col:9> col:5 o1 'O':'O' parenlistinit
`-ExprWithCleanups 0x62100006b250 <col:7, col:9> 'O':'O'
  `-CXXParenListInitExpr 0x62100006b210 <col:7, col:9> 'O':'O'
    `-MaterializeTemporaryExpr 0x62100006b1f0 <col:8> 'int' xvalue
      `-IntegerLiteral 0x62100006abd0 <col:8> 'int' 0

Before this patch, we create a local temporary variable for the
MaterializeTemporaryExpr and destroy it again when destroying the
EvalEmitter we create to interpret the initializer. However, since
O::j is a reference, this reference now points to a local variable
that doesn't exist anymore.

Differential Revision: https://reviews.llvm.org/D156453
parent 8505c3b1

clang/lib/AST/Interp/ByteCodeExprGen.cpp

+23 −6
Original line number Diff line number Diff line
@@ -29,14 +29,20 @@ namespace interp { 
template <class Emitter> class DeclScope final : public VariableScope<Emitter> {

public:

  DeclScope(ByteCodeExprGen<Emitter> *Ctx, const ValueDecl *VD)

      : VariableScope<Emitter>(Ctx), Scope(Ctx->P, VD) {}

      : VariableScope<Emitter>(Ctx), Scope(Ctx->P, VD),

        OldGlobalDecl(Ctx->GlobalDecl) {

    Ctx->GlobalDecl = Context::shouldBeGloballyIndexed(VD);

  }



  void addExtended(const Scope::Local &Local) override {

    return this->addLocal(Local);

  }



  ~DeclScope() { this->Ctx->GlobalDecl = OldGlobalDecl; }



private:

  Program::DeclScope Scope;

  bool OldGlobalDecl;

};



/// Scope used to handle initialization methods.
@@ -1198,21 +1204,30 @@ bool ByteCodeExprGen<Emitter>::VisitMaterializeTemporaryExpr( 
  if (DiscardResult)

    return this->discard(SubExpr);



  // When we're initializing a global variable *or* the storage duration of

  // the temporary is explicitly static, create a global variable.

  std::optional<PrimType> SubExprT = classify(SubExpr);

  if (E->getStorageDuration() == SD_Static) {

  bool IsStatic = E->getStorageDuration() == SD_Static;

  if (GlobalDecl || IsStatic) {

    std::optional<unsigned> GlobalIndex = P.createGlobal(E);

    if (!GlobalIndex)

      return false;



    const LifetimeExtendedTemporaryDecl *TempDecl =

        E->getLifetimeExtendedTemporaryDecl();

    if (IsStatic)

      assert(TempDecl);



    if (SubExprT) {

      if (!this->visit(SubExpr))

        return false;

      if (IsStatic) {

        if (!this->emitInitGlobalTemp(*SubExprT, *GlobalIndex, TempDecl, E))

          return false;

      } else {

        if (!this->emitInitGlobal(*SubExprT, *GlobalIndex, E))

          return false;

      }

      return this->emitGetPtrGlobal(*GlobalIndex, E);

    }
@@ -1221,7 +1236,9 @@ bool ByteCodeExprGen<Emitter>::VisitMaterializeTemporaryExpr( 
      return false;

    if (!this->visitInitializer(SubExpr))

      return false;

    if (IsStatic)

      return this->emitInitGlobalTempComp(TempDecl, E);

    return true;

  }



  // For everyhing else, use local variables.

clang/lib/AST/Interp/ByteCodeExprGen.h

+3 −0
Original line number Diff line number Diff line
@@ -304,6 +304,9 @@ protected: 
  /// Flag inidicating if we're initializing an already created

  /// variable. This is set in visitInitializer().

  bool Initializing = false;



  /// Flag indicating if we're initializing a global variable.

  bool GlobalDecl = false;

};



extern template class ByteCodeExprGen<ByteCodeEmitter>;

clang/test/AST/Interp/records.cpp

+16 −0
Original line number Diff line number Diff line
@@ -1064,6 +1064,22 @@ namespace ParenInit { 
  };



  constexpr B b(A(1),2);





  struct O {

    int &&j;

  };



  /// Not constexpr!

  O o1(0);

  constinit O o2(0); // ref-error {{variable does not have a constant initializer}} \

                     // ref-note {{required by 'constinit' specifier}} \

                     // ref-note {{reference to temporary is not a constant expression}} \

                     // ref-note {{temporary created here}} \

                     // expected-error {{variable does not have a constant initializer}} \

                     // expected-note {{required by 'constinit' specifier}} \

                     // expected-note {{reference to temporary is not a constant expression}} \

                     // expected-note {{temporary created here}}

}

#endif

clang/test/SemaCXX/paren-list-agg-init.cpp

+2 −0
Original line number Diff line number Diff line 
// RUN: %clang_cc1 -verify -std=c++20 %s -fsyntax-only

// RUN: %clang_cc1 -verify -std=c++20 %s -fsyntax-only -fexperimental-new-constant-interpreter

// RUN: %clang_cc1 -verify=expected,beforecxx20 -Wc++20-extensions -std=c++20 %s -fsyntax-only -fexperimental-new-constant-interpreter

// RUN: %clang_cc1 -verify=expected,beforecxx20 -Wc++20-extensions -std=c++20 %s -fsyntax-only



struct A { // expected-note 4{{candidate constructor}}