[cfe-commits] r167514 - in /cfe/trunk: lib/Sema/SemaExpr.cpp lib/Sema/SemaOverload.cpp test/SemaCXX/constant-expression-cxx11.cpp test/SemaCXX/implicit-exception-spec.cpp test/SemaTemplate/constexpr-instantiate.cpp
Richard Smith
richard at metafoo.co.uk
Wed Nov 14 14:56:17 PST 2012
On Wed, Nov 14, 2012 at 1:00 PM, Argyrios Kyrtzidis <kyrtzidis at apple.com> wrote:
> Hi Richard,
>
> I think this caused a regression, could you take a look at http://llvm.org/bugs/show_bug.cgi?id=14340 ?
That's not a regression, we've found another bug in libstdc++'s
<chrono> implementation. I'm thinking about ways to avoid erroring on
that broken code.
> -Argyrios
>
> On Nov 6, 2012, at 5:14 PM, Richard Smith <richard-llvm at metafoo.co.uk> wrote:
>
>> Author: rsmith
>> Date: Tue Nov 6 19:14:25 2012
>> New Revision: 167514
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=167514&view=rev
>> Log:
>> PR11851 (and duplicates): Whenever a constexpr function is referenced,
>> instantiate it if it can be instantiated and implicitly define it if it can be
>> implicitly defined. This matches g++'s approach. Remove some cases from
>> SemaOverload which were marking functions as referenced when just planning how
>> overload resolution would proceed; such cases are not actually references.
>>
>> Modified:
>> cfe/trunk/lib/Sema/SemaExpr.cpp
>> cfe/trunk/lib/Sema/SemaOverload.cpp
>> cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp
>> cfe/trunk/test/SemaCXX/implicit-exception-spec.cpp
>> cfe/trunk/test/SemaTemplate/constexpr-instantiate.cpp
>>
>> Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=167514&r1=167513&r2=167514&view=diff
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaExpr.cpp Tue Nov 6 19:14:25 2012
>> @@ -10340,15 +10340,44 @@
>>
>> Func->setReferenced();
>>
>> - // Don't mark this function as used multiple times, unless it's a constexpr
>> - // function which we need to instantiate.
>> - if (Func->isUsed(false) &&
>> - !(Func->isConstexpr() && !Func->getBody() &&
>> - Func->isImplicitlyInstantiable()))
>> - return;
>> -
>> - if (!IsPotentiallyEvaluatedContext(*this))
>> - return;
>> + // C++11 [basic.def.odr]p3:
>> + // A function whose name appears as a potentially-evaluated expression is
>> + // odr-used if it is the unique lookup result or the selected member of a
>> + // set of overloaded functions [...].
>> + //
>> + // We (incorrectly) mark overload resolution as an unevaluated context, so we
>> + // can just check that here. Skip the rest of this function if we've already
>> + // marked the function as used.
>> + if (Func->isUsed(false) || !IsPotentiallyEvaluatedContext(*this)) {
>> + // C++11 [temp.inst]p3:
>> + // Unless a function template specialization has been explicitly
>> + // instantiated or explicitly specialized, the function template
>> + // specialization is implicitly instantiated when the specialization is
>> + // referenced in a context that requires a function definition to exist.
>> + //
>> + // We consider constexpr function templates to be referenced in a context
>> + // that requires a definition to exist whenever they are referenced.
>> + //
>> + // FIXME: This instantiates constexpr functions too frequently. If this is
>> + // really an unevaluated context (and we're not just in the definition of a
>> + // function template or overload resolution or other cases which we
>> + // incorrectly consider to be unevaluated contexts), and we're not in a
>> + // subexpression which we actually need to evaluate (for instance, a
>> + // template argument, array bound or an expression in a braced-init-list),
>> + // we are not permitted to instantiate this constexpr function definition.
>> + //
>> + // FIXME: This also implicitly defines special members too frequently. They
>> + // are only supposed to be implicitly defined if they are odr-used, but they
>> + // are not odr-used from constant expressions in unevaluated contexts.
>> + // However, they cannot be referenced if they are deleted, and they are
>> + // deleted whenever the implicit definition of the special member would
>> + // fail.
>> + if (!Func->isConstexpr() || Func->getBody())
>> + return;
>> + CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(Func);
>> + if (!Func->isImplicitlyInstantiable() && (!MD || MD->isUserProvided()))
>> + return;
>> + }
>>
>> // Note that this declaration has been used.
>> if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(Func)) {
>>
>> Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOverload.cpp?rev=167514&r1=167513&r2=167514&view=diff
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaOverload.cpp Tue Nov 6 19:14:25 2012
>> @@ -2923,8 +2923,6 @@
>> case OR_Success: {
>> // Record the standard conversion we used and the conversion function.
>> CXXConstructorDecl *Constructor = cast<CXXConstructorDecl>(Best->Function);
>> - S.MarkFunctionReferenced(From->getLocStart(), Constructor);
>> -
>> QualType ThisType = Constructor->getThisType(S.Context);
>> // Initializer lists don't have conversions as such.
>> User.Before.setAsIdentityConversion();
>> @@ -3105,8 +3103,6 @@
>> // Record the standard conversion we used and the conversion function.
>> if (CXXConstructorDecl *Constructor
>> = dyn_cast<CXXConstructorDecl>(Best->Function)) {
>> - S.MarkFunctionReferenced(From->getLocStart(), Constructor);
>> -
>> // C++ [over.ics.user]p1:
>> // If the user-defined conversion is specified by a
>> // constructor (12.3.1), the initial standard conversion
>> @@ -3135,8 +3131,6 @@
>> }
>> if (CXXConversionDecl *Conversion
>> = dyn_cast<CXXConversionDecl>(Best->Function)) {
>> - S.MarkFunctionReferenced(From->getLocStart(), Conversion);
>> -
>> // C++ [over.ics.user]p1:
>> //
>> // [...] If the user-defined conversion is specified by a
>> @@ -4049,8 +4043,6 @@
>> if (!Best->FinalConversion.DirectBinding)
>> return false;
>>
>> - if (Best->Function)
>> - S.MarkFunctionReferenced(DeclLoc, Best->Function);
>> ICS.setUserDefined();
>> ICS.UserDefined.Before = Best->Conversions[0].Standard;
>> ICS.UserDefined.After = Best->FinalConversion;
>> @@ -9225,7 +9217,6 @@
>> Fn = Resolver.getMatchingFunctionDecl();
>> assert(Fn);
>> FoundResult = *Resolver.getMatchingFunctionAccessPair();
>> - MarkFunctionReferenced(AddressOfExpr->getLocStart(), Fn);
>> if (Complain)
>> CheckAddressOfMemberAccess(AddressOfExpr, FoundResult);
>> }
>>
>> Modified: cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp?rev=167514&r1=167513&r2=167514&view=diff
>> ==============================================================================
>> --- cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp (original)
>> +++ cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp Tue Nov 6 19:14:25 2012
>> @@ -1451,6 +1451,7 @@
>> }
>> // FIXME: It's unclear whether this is valid. On the one hand, we're not
>> // allowed to generate a move constructor. On the other hand, if we did,
>> - // this would be a constant expression.
>> - int n = sizeof(short{duration(duration())}); // expected-error {{non-constant-expression cannot be narrowed}} expected-note {{override}}
>> + // this would be a constant expression. For now, we generate a move
>> + // constructor here.
>> + int n = sizeof(short{duration(duration())});
>> }
>>
>> Modified: cfe/trunk/test/SemaCXX/implicit-exception-spec.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/implicit-exception-spec.cpp?rev=167514&r1=167513&r2=167514&view=diff
>> ==============================================================================
>> --- cfe/trunk/test/SemaCXX/implicit-exception-spec.cpp (original)
>> +++ cfe/trunk/test/SemaCXX/implicit-exception-spec.cpp Tue Nov 6 19:14:25 2012
>> @@ -30,20 +30,17 @@
>> bool x = noexcept(TemplateArg());
>>
>> // And within a nested class.
>> - // FIXME: The diagnostic location is terrible here.
>> - struct Nested {
>> + struct Nested { // expected-error {{cannot be used by non-static data member initializer}}
>> struct Inner {
>> - int n = ExceptionIf<noexcept(Nested())>::f();
>> - } inner; // expected-error {{cannot be used by non-static data member initializer}}
>> + int n = ExceptionIf<noexcept(Nested())>::f(); // expected-note {{implicit default constructor for 'InClassInitializers::Nested' first required here}}
>> + } inner;
>> };
>> - bool y = noexcept(Nested());
>> - bool z = noexcept(Nested::Inner());
>>
>> struct Nested2 {
>> struct Inner;
>> int n = Inner().n; // expected-error {{cannot be used by non-static data member initializer}}
>> struct Inner {
>> - int n = ExceptionIf<noexcept(Nested())>::f();
>> + int n = ExceptionIf<noexcept(Nested2())>::f();
>> } inner;
>> };
>> }
>>
>> Modified: cfe/trunk/test/SemaTemplate/constexpr-instantiate.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaTemplate/constexpr-instantiate.cpp?rev=167514&r1=167513&r2=167514&view=diff
>> ==============================================================================
>> --- cfe/trunk/test/SemaTemplate/constexpr-instantiate.cpp (original)
>> +++ cfe/trunk/test/SemaTemplate/constexpr-instantiate.cpp Tue Nov 6 19:14:25 2012
>> @@ -75,3 +75,136 @@
>> constexpr int n = const_cast<int&>(S<int>::r);
>> static_assert(n == 5, "");
>> }
>> +
>> +namespace Unevaluated {
>> + // We follow g++ in treating any reference to a constexpr function template
>> + // specialization as requiring an instantiation, even if it occurs in an
>> + // unevaluated context.
>> + //
>> + // We go slightly further than g++, and also trigger the implicit definition
>> + // of a defaulted special member in the same circumstances. This seems scary,
>> + // since a lot of classes have constexpr special members in C++11, but the
>> + // only observable impact should be the implicit instantiation of constexpr
>> + // special member templates (defaulted special members should only be
>> + // generated if they are well-formed, and non-constexpr special members in a
>> + // base or member cause the class's special member to not be constexpr).
>> + //
>> + // FIXME: None of this is required by the C++ standard. The rules in this
>> + // area are poorly specified, so this is subject to change.
>> + namespace NotConstexpr {
>> + template<typename T> struct S {
>> + S() : n(0) {}
>> + S(const S&) : n(T::error) {}
>> + int n;
>> + };
>> + struct U : S<int> {};
>> + decltype(U(U())) u; // ok, don't instantiate S<int>::S() because it wasn't declared constexpr
>> + }
>> + namespace Constexpr {
>> + template<typename T> struct S {
>> + constexpr S() : n(0) {}
>> + constexpr S(const S&) : n(T::error) {} // expected-error {{has no members}}
>> + int n;
>> + };
>> + struct U : S<int> {}; // expected-note {{instantiation}}
>> + decltype(U(U())) u; // expected-note {{here}}
>> + }
>> +
>> + namespace PR11851_Comment0 {
>> + template<int x> constexpr int f() { return x; }
>> + template<int i> void ovf(int (&x)[f<i>()]);
>> + void f() { int x[10]; ovf<10>(x); }
>> + }
>> +
>> + namespace PR11851_Comment1 {
>> + template<typename T>
>> + constexpr bool Integral() {
>> + return true;
>> + }
>> + template<typename T, bool Int = Integral<T>()>
>> + struct safe_make_unsigned {
>> + typedef T type;
>> + };
>> + template<typename T>
>> + using Make_unsigned = typename safe_make_unsigned<T>::type;
>> + template <typename T>
>> + struct get_distance_type {
>> + using type = int;
>> + };
>> + template<typename R>
>> + auto size(R) -> Make_unsigned<typename get_distance_type<R>::type>;
>> + auto check() -> decltype(size(0));
>> + }
>> +
>> + namespace PR11851_Comment6 {
>> + template<int> struct foo {};
>> + template<class> constexpr int bar() { return 0; }
>> + template<class T> foo<bar<T>()> foobar();
>> + auto foobar_ = foobar<int>();
>> + }
>> +
>> + namespace PR11851_Comment9 {
>> + struct S1 {
>> + constexpr S1() {}
>> + constexpr operator int() const { return 0; }
>> + };
>> + int k1 = sizeof(short{S1(S1())});
>> +
>> + struct S2 {
>> + constexpr S2() {}
>> + constexpr operator int() const { return 123456; }
>> + };
>> + int k2 = sizeof(short{S2(S2())}); // expected-error {{cannot be narrowed}} expected-note {{override}}
>> + }
>> +
>> + namespace PR12288 {
>> + template <typename> constexpr bool foo() { return true; }
>> + template <bool> struct bar {};
>> + template <typename T> bar<foo<T>()> baz() { return bar<foo<T>()>(); }
>> + int main() { baz<int>(); }
>> + }
>> +
>> + namespace PR13423 {
>> + template<bool, typename> struct enable_if {};
>> + template<typename T> struct enable_if<true, T> { using type = T; };
>> +
>> + template<typename T> struct F {
>> + template<typename U>
>> + static constexpr bool f() { return sizeof(T) < U::size; }
>> +
>> + template<typename U>
>> + static typename enable_if<f<U>(), void>::type g() {} // expected-note {{disabled by 'enable_if'}}
>> + };
>> +
>> + struct U { static constexpr int size = 2; };
>> +
>> + void h() { F<char>::g<U>(); }
>> + void i() { F<int>::g<U>(); } // expected-error {{no matching function}}
>> + }
>> +
>> + namespace PR14203 {
>> + struct duration { constexpr duration() {} };
>> +
>> + template <typename>
>> + void sleep_for() {
>> + constexpr duration max = duration();
>> + }
>> + }
>> +}
>> +
>> +namespace NoInstantiationWhenSelectingOverload {
>> + // Check that we don't instantiate conversion functions when we're checking
>> + // for the existence of an implicit conversion sequence, only when a function
>> + // is actually chosen by overload resolution.
>> + struct S {
>> + template<typename T> constexpr S(T) : n(T::error) {} // expected-error {{no members}}
>> + int n;
>> + };
>> +
>> + void f(S);
>> + void f(int);
>> +
>> + void g() { f(0); }
>> + void h() { (void)sizeof(f(0)); }
>> + void i() { (void)sizeof(f("oops")); } // expected-note {{instantiation of}}
>> +}
>>
>>
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