Index: lib/AST/ExprConstant.cpp =================================================================== --- lib/AST/ExprConstant.cpp +++ lib/AST/ExprConstant.cpp @@ -4748,14 +4748,20 @@ } bool LValueExprEvaluator::VisitMemberExpr(const MemberExpr *E) { + ValueDecl *MemberDecl = E->getMemberDecl(); + ASTContext &Ctx = MemberDecl->getASTContext(); + // Handle static data members. - if (const VarDecl *VD = dyn_cast(E->getMemberDecl())) { - VisitIgnoredValue(E->getBase()); + if (const auto *VD = dyn_cast(MemberDecl)) { + // While MSVC doesn't evaluate the base expression, it does diagnose the + // presence of side-effecting behavior. + if (!Info.getLangOpts().MSVCCompat || E->getBase()->HasSideEffects(Ctx)) + VisitIgnoredValue(E->getBase()); return VisitVarDecl(E, VD); } // Handle static member functions. - if (const CXXMethodDecl *MD = dyn_cast(E->getMemberDecl())) { + if (const auto *MD = dyn_cast(MemberDecl)) { if (MD->isStatic()) { VisitIgnoredValue(E->getBase()); return Success(MD); @@ -6077,8 +6083,14 @@ return ExprEvaluatorBaseTy::VisitDeclRefExpr(E); } bool VisitMemberExpr(const MemberExpr *E) { - if (CheckReferencedDecl(E, E->getMemberDecl())) { - VisitIgnoredValue(E->getBase()); + ValueDecl *MemberDecl = E->getMemberDecl(); + ASTContext &Ctx = MemberDecl->getASTContext(); + if (CheckReferencedDecl(E, MemberDecl)) { + // While MSVC doesn't evaluate the base expression, it does diagnose the + // presence of side-effecting behavior. + if (!Info.getLangOpts().MSVCCompat || E->getBase()->HasSideEffects(Ctx)) { + VisitIgnoredValue(E->getBase()); + } return true; } Index: test/SemaCXX/ms-const-member-expr.cpp =================================================================== --- /dev/null +++ test/SemaCXX/ms-const-member-expr.cpp @@ -0,0 +1,19 @@ +// RUN: %clang_cc1 %s -std=c++11 -fms-compatibility -fsyntax-only -verify + +struct S { + enum { E = 1 }; + static const int sdm = 1; +}; + +void f(S *s) { + char array[s->E] = { 0 }; +} + +extern S *s; +constexpr int e1 = s->E; + +S *side_effect(); // expected-note{{declared here}} +constexpr int e2 = // expected-error{{must be initialized by a constant expression}} + side_effect()->E; // expected-note{{cannot be used in a constant expression}} + +constexpr int e4 = s->sdm;