<functional>: Constrain functions used by std::bind (#3577)

Co-authored-by: Stephan T. Lavavej <stl@nuwen.net>
microsoft · Mar 28, 2023 · e863967 · e863967
1 parent 6645bc3
commit e863967
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Showing 4 changed files with 78 additions and 12 deletions.
diff --git a/stl/inc/functional b/stl/inc/functional
@@ -647,7 +647,8 @@ struct _Unforced { // tag to distinguish bind() from bind<R>()
 // helper to give INVOKE an explicit return type; avoids undesirable Expression SFINAE
 template <class _Rx>
 struct _Invoker_ret { // selected for all _Rx other than _Unforced
-    template <class _Fx, class... _Valtys>
+    template <class _Fx, class... _Valtys,
+        enable_if_t<_Select_invoke_traits<_Fx, _Valtys...>::template _Is_invocable_r<_Rx>::value, int> = 0>
     static _CONSTEXPR20 _Rx _Call(_Fx&& _Func, _Valtys&&... _Vals) noexcept(_Select_invoke_traits<_Fx,
         _Valtys...>::template _Is_nothrow_invocable_r<_Rx>::value) { // INVOKE, implicitly converted
         if constexpr (is_void_v<_Rx>) {
@@ -760,7 +761,11 @@ private:
     }
 
     _Rx _Do_call(_Types&&... _Args) override { // call wrapped function
-        return _Invoker_ret<_Rx>::_Call(_Mypair._Myval2, _STD forward<_Types>(_Args)...);
+        if constexpr (is_void_v<_Rx>) {
+            (void) _STD invoke(_Mypair._Myval2, _STD forward<_Types>(_Args)...);
+        } else {
+            return _STD invoke(_Mypair._Myval2, _STD forward<_Types>(_Args)...);
+        }
     }
 
     const type_info& _Target_type() const noexcept override {
@@ -817,7 +822,11 @@ private:
     }
 
     _Rx _Do_call(_Types&&... _Args) override { // call wrapped function
-        return _Invoker_ret<_Rx>::_Call(_Callee, _STD forward<_Types>(_Args)...);
+        if constexpr (is_void_v<_Rx>) {
+            (void) _STD invoke(_Callee, _STD forward<_Types>(_Args)...);
+        } else {
+            return _STD invoke(_Callee, _STD forward<_Types>(_Args)...);
+        }
     }
 
     const type_info& _Target_type() const noexcept override {
@@ -1232,14 +1241,20 @@ template <class _Rx, class... _Types>
 
 template <class _Vt, class _VtInvQuals, class _Rx, bool _Noex, class... _Types>
 _NODISCARD _Rx __stdcall _Function_inv_small(const _Move_only_function_data& _Self, _Types&&... _Args) noexcept(_Noex) {
-    return _Invoker_ret<_Rx>::_Call(
-        static_cast<_VtInvQuals>(*_Self._Small_fn_ptr<_Vt>()), _STD forward<_Types>(_Args)...);
+    if constexpr (is_void_v<_Rx>) {
+        (void) _STD invoke(static_cast<_VtInvQuals>(*_Self._Small_fn_ptr<_Vt>()), _STD forward<_Types>(_Args)...);
+    } else {
+        return _STD invoke(static_cast<_VtInvQuals>(*_Self._Small_fn_ptr<_Vt>()), _STD forward<_Types>(_Args)...);
+    }
 }
 
 template <class _Vt, class _VtInvQuals, class _Rx, bool _Noex, class... _Types>
 _NODISCARD _Rx __stdcall _Function_inv_large(const _Move_only_function_data& _Self, _Types&&... _Args) noexcept(_Noex) {
-    return _Invoker_ret<_Rx>::_Call(
-        static_cast<_VtInvQuals>(*_Self._Large_fn_ptr<_Vt>()), _STD forward<_Types>(_Args)...);
+    if constexpr (is_void_v<_Rx>) {
+        (void) _STD invoke(static_cast<_VtInvQuals>(*_Self._Large_fn_ptr<_Vt>()), _STD forward<_Types>(_Args)...);
+    } else {
+        return _STD invoke(static_cast<_VtInvQuals>(*_Self._Large_fn_ptr<_Vt>()), _STD forward<_Types>(_Args)...);
+    }
 }
 
 template <class _Vt>
@@ -1910,7 +1925,8 @@ struct _Select_fixer<_Cv_TiD, true, false, 0> { // reference_wrapper fixer
 
 template <class _Cv_TiD>
 struct _Select_fixer<_Cv_TiD, false, true, 0> { // nested bind fixer
-    template <class _Untuple, size_t... _Jx>
+    template <class _Untuple, size_t... _Jx,
+        enable_if_t<conjunction_v<bool_constant<(_Jx < tuple_size_v<_Untuple>)>...>, int> = 0>
     static constexpr auto _Apply(_Cv_TiD& _Tid, _Untuple&& _Ut, index_sequence<_Jx...>) noexcept(
         noexcept(_Tid(_STD get<_Jx>(_STD move(_Ut))...))) -> decltype(_Tid(_STD get<_Jx>(_STD move(_Ut))...)) {
         // call a nested bind expression
@@ -1939,7 +1955,7 @@ template <class _Cv_TiD, int _Jx>
 struct _Select_fixer<_Cv_TiD, false, false, _Jx> { // placeholder fixer
     static_assert(_Jx > 0, "invalid is_placeholder value");
 
-    template <class _Untuple>
+    template <class _Untuple, enable_if_t<(_Jx <= tuple_size_v<_Untuple>), int> = 0>
     static constexpr auto _Fix(_Cv_TiD&, _Untuple&& _Ut) noexcept
         -> decltype(_STD get<_Jx - 1>(_STD move(_Ut))) { // choose the Jth unbound argument (1-based indexing)
         return _STD get<_Jx - 1>(_STD move(_Ut));
@@ -1956,10 +1972,10 @@ constexpr auto _Fix_arg(_Cv_TiD& _Tid, _Untuple&& _Ut) noexcept(
 template <class _Ret, size_t... _Ix, class _Cv_FD, class _Cv_tuple_TiD, class _Untuple>
 _CONSTEXPR20 auto _Call_binder(_Invoker_ret<_Ret>, index_sequence<_Ix...>, _Cv_FD& _Obj, _Cv_tuple_TiD& _Tpl,
     _Untuple&& _Ut) noexcept(noexcept(_Invoker_ret<_Ret>::_Call(_Obj,
-    _Fix_arg(_STD get<_Ix>(_Tpl), _STD move(_Ut))...)))
-    -> decltype(_Invoker_ret<_Ret>::_Call(_Obj, _Fix_arg(_STD get<_Ix>(_Tpl), _STD move(_Ut))...)) {
+    _STD _Fix_arg(_STD get<_Ix>(_Tpl), _STD move(_Ut))...)))
+    -> decltype(_Invoker_ret<_Ret>::_Call(_Obj, _STD _Fix_arg(_STD get<_Ix>(_Tpl), _STD move(_Ut))...)) {
     // bind() and bind<R>() invocation
-    return _Invoker_ret<_Ret>::_Call(_Obj, _Fix_arg(_STD get<_Ix>(_Tpl), _STD move(_Ut))...);
+    return _Invoker_ret<_Ret>::_Call(_Obj, _STD _Fix_arg(_STD get<_Ix>(_Tpl), _STD move(_Ut))...);
 }
 
 template <class _Ret>

diff --git a/tests/std/test.lst b/tests/std/test.lst
@@ -174,6 +174,7 @@ tests\GH_000690_overaligned_function
 tests\GH_000890_pow_template
 tests\GH_000935_complex_numerical_accuracy
 tests\GH_000940_missing_valarray_copy
+tests\GH_000952_bind_constraints
 tests\GH_000990_any_link_without_exceptions
 tests\GH_001001_random_rejection_rounding
 tests\GH_001010_filesystem_error_encoding

diff --git a/tests/std/tests/GH_000952_bind_constraints/env.lst b/tests/std/tests/GH_000952_bind_constraints/env.lst
@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\usual_matrix.lst
diff --git a/tests/std/tests/GH_000952_bind_constraints/test.compile.pass.cpp b/tests/std/tests/GH_000952_bind_constraints/test.compile.pass.cpp
@@ -0,0 +1,45 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <functional>
+#include <type_traits>
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+using namespace std;
+
+void test() { // COMPILE-ONLY
+    {
+        auto lambda = [](int) {};
+        auto f      = bind(lambda, placeholders::_1);
+        STATIC_ASSERT(!is_convertible_v<decltype(f), function<void()>>);
+        STATIC_ASSERT(!is_convertible_v<decltype(f), function<void*(int)>>);
+        STATIC_ASSERT(is_convertible_v<decltype(f), function<void(int)>>);
+        STATIC_ASSERT(!is_convertible_v<decltype(f), function<char(int)>>);
+    }
+    {
+        auto lambda = [](int) { return 42; };
+        auto f      = bind<void>(lambda, placeholders::_1);
+        STATIC_ASSERT(!is_convertible_v<decltype(f), function<void()>>);
+        STATIC_ASSERT(!is_convertible_v<decltype(f), function<void*(int)>>);
+        STATIC_ASSERT(is_convertible_v<decltype(f), function<void(int)>>);
+        STATIC_ASSERT(!is_convertible_v<decltype(f), function<char(int)>>);
+    }
+    {
+        auto lambda = [](int) { return 42; };
+        auto f      = bind<long>(lambda, placeholders::_1);
+        STATIC_ASSERT(!is_convertible_v<decltype(f), function<void()>>);
+        STATIC_ASSERT(!is_convertible_v<decltype(f), function<void*(int)>>);
+        STATIC_ASSERT(is_convertible_v<decltype(f), function<void(int)>>);
+        STATIC_ASSERT(is_convertible_v<decltype(f), function<char(int)>>);
+    }
+    {
+        auto lambda0 = [](int, int) { return true; };
+        auto lambda1 = [](const char*) { return 0; };
+        auto f       = bind(lambda0, placeholders::_1, bind(lambda1, placeholders::_2));
+        STATIC_ASSERT(!is_convertible_v<decltype(f), function<void()>>);
+        STATIC_ASSERT(!is_convertible_v<decltype(f), function<void*(int, const char*)>>);
+        STATIC_ASSERT(is_convertible_v<decltype(f), function<void(int, const char*)>>);
+        STATIC_ASSERT(is_convertible_v<decltype(f), function<bool(int, const char*)>>);
+    }
+}