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[24.228.8.148]) by smtp.gmail.com with ESMTPSA id 1sm1269351qtg.62.2022.01.27.06.02.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Jan 2022 06:02:33 -0800 (PST) From: Patrick Palka X-Google-Original-From: Patrick Palka Date: Thu, 27 Jan 2022 09:02:32 -0500 (EST) To: Patrick Palka cc: Jason Merrill , GCC Patches Subject: Re: [PATCH] c++: non-dependent immediate member fn call [PR99895] In-Reply-To: <934c1d0f-2bc5-4e69-6fd4-cad21fc1f5b7@idea> Message-ID: References: <20220119161542.1259608-1-ppalka@redhat.com> <934c1d0f-2bc5-4e69-6fd4-cad21fc1f5b7@idea> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-14.6 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-Content-Filtered-By: Mailman/MimeDel 2.1.29 X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Jan 2022 14:02:42 -0000 On Wed, 26 Jan 2022, Patrick Palka wrote: > On Wed, 26 Jan 2022, Patrick Palka wrote: > > > On Wed, Jan 19, 2022 at 2:19 PM Jason Merrill wrote: > > > > > > On 1/19/22 11:15, Patrick Palka wrote: > > > > Here we're emitting a bogus error during ahead of time evaluation of a > > > > non-dependent immediate member function call such as a.f(args) because > > > > the defacto templated form for such a call is (a.f)(args) but we're > > > > trying to evaluate it using the intermediate CALL_EXPR built by > > > > build_over_call, which has the non-member form f(a, args). The defacto > > > > member form is built in build_new_method_call, so it seems we should > > > > handle the immediate call there instead. > > > > > > Hmm, there's already a bunch of code in build_over_call to try to fix up > > > the object argument, and there seem to be many places other than > > > build_new_method_call that call build_over_call for member functions; I > > > think it's probably better to build the needed COMPONENT_REF in > > > build_over_call. > > > > Ah, but in build_over_call the arguments (including the implicit > > object argument) are potentially wrapped in a NON_DEPENDENT_EXPR. So > > even if we built a COMPONENT_REF in build_over_call, we'd have to > > keep rebuilding the entire CALL_EXPR (including the COMPONENT_REF) in > > terms of the original arguments in build_new_method_call, IIUC. > > > > On a related note, the NON_DEPENDENT_EXPR wrapping seems to be a > > problem for non-member functions too, because the constexpr engine > > punts on them: > > > > struct fixed_string { }; > > > > static consteval void size(fixed_string) { } > > > > template > > void VerifyHash(fixed_string s) { > > size(s); // error: expression ‘s’ is not a constant expression > > (because it's wrapped in NON_DEPENDENT_EXPR) > > } > > > > I wonder if this means we should be evaluating non-dependent > > non-member immediate calls elsewhere, e.g. in finish_call_expr? Or > > perhaps we should stop punting on NON_DEPENDENT_EXPR during constexpr > > evaluation? > > Actually, for that particular example, we probably should just avoid > wrapping PARM_DECL in a NON_DEPENDENT_EXPR... Here's a patch that makes build_over_call build the COMPONENT_REF-using form for non-dependent member calls, and in passing makes us avoid wrapping PARM_DECL in a NON_DEPENDENT_EXPR. -- >8 -- Subject: [PATCH] c++: non-dependent immediate member fn call [PR99895] Here we're emitting a bogus error during ahead of time evaluation of a non-dependent immediate member function call such as a.f(args) because the defacto templated form for such a call is (a.f)(args) but we're trying to evaluate it using the intermediate CALL_EXPR built by build_over_call, which has the non-member form f(a, args). The defacto member form is built in build_new_method_call, so it seems we should handle the immediate call there instead, or perhaps make build_over_call build the correct form in the first place. Giiven that there are many spots other than build_new_method_call that call build_over_call for member functions, this patch takes the latter approach. In passing, this patch makes us avoid wrapping PARM_DECL in NON_DEPENDENT_EXPR for benefit of the third testcase below. Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk? PR c++/99895 gcc/cp/ChangeLog: * call.cc (build_over_call): For a non-dependent member call, build up a CALL_EXPR using a COMPONENT_REF callee, as in build_new_method_call. * pt.cc (build_non_dependent_expr): Don't wrap PARM_DECL either. * tree.cc (build_min_non_dep_op_overload): Adjust accordingly after the build_over_call change. gcc/ChangeLog: * tree.cc (build_call_vec): Add const to second parameter. * tree.h (build_call_vec): Likewise. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/consteval-memfn1.C: New test. * g++.dg/cpp2a/consteval-memfn2.C: New test. * g++.dg/cpp2a/consteval28.C: New test. --- gcc/cp/call.cc | 38 +++++++------------ gcc/cp/pt.cc | 6 ++- gcc/cp/tree.cc | 5 ++- gcc/testsuite/g++.dg/cpp2a/consteval-memfn1.C | 27 +++++++++++++ gcc/testsuite/g++.dg/cpp2a/consteval-memfn2.C | 34 +++++++++++++++++ gcc/testsuite/g++.dg/cpp2a/consteval28.C | 10 +++++ gcc/tree.cc | 2 +- gcc/tree.h | 2 +- 8 files changed, 94 insertions(+), 30 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/consteval-memfn1.C create mode 100644 gcc/testsuite/g++.dg/cpp2a/consteval-memfn2.C create mode 100644 gcc/testsuite/g++.dg/cpp2a/consteval28.C diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc index bc157cdd1fb..b2e89c5d783 100644 --- a/gcc/cp/call.cc +++ b/gcc/cp/call.cc @@ -9204,11 +9204,6 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain) errors will be deferred until the template is instantiated. */ if (processing_template_decl) { - tree expr, addr; - tree return_type; - const tree *argarray; - unsigned int nargs; - if (undeduced_auto_decl (fn)) mark_used (fn, complain); else @@ -9216,32 +9211,27 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain) See PR80598. */ TREE_USED (fn) = 1; - return_type = TREE_TYPE (TREE_TYPE (fn)); - nargs = vec_safe_length (args); + tree return_type = TREE_TYPE (TREE_TYPE (fn)); + tree callee; if (first_arg == NULL_TREE) - argarray = args->address (); + { + callee = build_addr_func (fn, complain); + if (callee == error_mark_node) + return error_mark_node; + } else { - tree *alcarray; - unsigned int ix; - tree arg; - - ++nargs; - alcarray = XALLOCAVEC (tree, nargs); - alcarray[0] = build_this (first_arg); - FOR_EACH_VEC_SAFE_ELT (args, ix, arg) - alcarray[ix + 1] = arg; - argarray = alcarray; + tree binfo = TYPE_BINFO (TREE_TYPE (first_arg)); + callee = build_baselink (binfo, binfo, fn, NULL_TREE); + callee = build_min (COMPONENT_REF, TREE_TYPE (fn), + first_arg, callee, NULL_TREE); } - addr = build_addr_func (fn, complain); - if (addr == error_mark_node) - return error_mark_node; - expr = build_call_array_loc (input_location, return_type, - addr, nargs, argarray); + tree expr = build_call_vec (return_type, callee, args); + SET_EXPR_LOCATION (expr, input_location); if (TREE_THIS_VOLATILE (fn) && cfun) current_function_returns_abnormally = 1; - if (immediate_invocation_p (fn, nargs)) + if (immediate_invocation_p (fn, vec_safe_length (args))) { tree obj_arg = NULL_TREE, exprimm = expr; if (DECL_CONSTRUCTOR_P (fn)) diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index 6fbda676527..19e73b3b77d 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -28410,8 +28410,10 @@ build_non_dependent_expr (tree expr) if (is_overloaded_fn (inner_expr) || TREE_CODE (inner_expr) == OFFSET_REF) return orig_expr; - /* There is no need to return a proxy for a variable or enumerator. */ - if (VAR_P (expr) || TREE_CODE (expr) == CONST_DECL) + /* There is no need to return a proxy for a variable, parameter + or enumerator. */ + if (VAR_P (expr) || TREE_CODE (expr) == PARM_DECL + || TREE_CODE (expr) == CONST_DECL) return orig_expr; /* Preserve string constants; conversions from string constants to "char *" are allowed, even though normally a "const char *" diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc index 5d453e49717..056f10f13b4 100644 --- a/gcc/cp/tree.cc +++ b/gcc/cp/tree.cc @@ -3661,6 +3661,8 @@ build_min_non_dep_op_overload (enum tree_code op, nargs = call_expr_nargs (non_dep); expected_nargs = cp_tree_code_length (op); + if (TREE_CODE (TREE_TYPE (overload)) == METHOD_TYPE) + expected_nargs -= 1; if ((op == POSTINCREMENT_EXPR || op == POSTDECREMENT_EXPR) /* With -fpermissive non_dep could be operator++(). */ @@ -3687,7 +3689,7 @@ build_min_non_dep_op_overload (enum tree_code op, tree method = build_baselink (binfo, binfo, overload, NULL_TREE); fn = build_min (COMPONENT_REF, TREE_TYPE (overload), object, method, NULL_TREE); - for (int i = 1; i < nargs; i++) + for (int i = 0; i < nargs; i++) { tree arg = va_arg (p, tree); vec_safe_push (args, arg); @@ -3723,7 +3725,6 @@ build_min_non_dep_op_overload (tree non_dep, tree overload, tree object, tree method = build_baselink (binfo, binfo, overload, NULL_TREE); tree fn = build_min (COMPONENT_REF, TREE_TYPE (overload), object, method, NULL_TREE); - nargs--; gcc_assert (vec_safe_length (args) == nargs); tree call = build_min_non_dep_call_vec (non_dep, fn, args); diff --git a/gcc/testsuite/g++.dg/cpp2a/consteval-memfn1.C b/gcc/testsuite/g++.dg/cpp2a/consteval-memfn1.C new file mode 100644 index 00000000000..910e7a1ac1e --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/consteval-memfn1.C @@ -0,0 +1,27 @@ +// PR c++/99895 +// { dg-do compile { target c++20 } } + +struct fixed_string { + consteval int size(int n) const { + if (n < 0) throw; // { dg-error "not a constant" } + return n; + } + + static consteval int size_static(int n) { + if (n < 0) throw; // { dg-error "not a constant" } + return n; + } + + consteval void operator()() const { } +}; + +template +void VerifyHash(fixed_string s) { + s.size(0); // { dg-bogus "" } + s.size(-1); // { dg-message "expansion of" } + s.size_static(0); // { dg-bogus "" } + s.size_static(-1); // { dg-message "expansion of" } + fixed_string::size_static(0); // { dg-bogus "" } + fixed_string::size_static(-1); // { dg-message "expansion of" } + s(); // { dg-bogus "" } +} diff --git a/gcc/testsuite/g++.dg/cpp2a/consteval-memfn2.C b/gcc/testsuite/g++.dg/cpp2a/consteval-memfn2.C new file mode 100644 index 00000000000..71748f46b13 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/consteval-memfn2.C @@ -0,0 +1,34 @@ +// PR c++/99895 +// { dg-do compile { target c++20 } } + +static constexpr unsigned hash(const char* s, unsigned length) +{ + s=s; + return length; +} +template +struct fixed_string +{ + constexpr fixed_string(const char (&s)[N]) + { + for (int i = 0; i < N; i++) + str[i] = s[i]; + } + consteval const char* data() const { return str; } + consteval unsigned size() const { return N-1; } + char str[N]; +}; +template +static consteval void VerifyHash() +{ + ( + [](auto){static_assert(hash(s.data(), s.size()) == expected_hash);}(s) + ,...); + // The compiler mistakenly translates s.data() into s.data(&s) + // and then complains that the call is not valid, because + // the function expects 0 parameters and 1 "was provided". +} +void foo() +{ + VerifyHash<5, "khaki", "plums">(); +} diff --git a/gcc/testsuite/g++.dg/cpp2a/consteval28.C b/gcc/testsuite/g++.dg/cpp2a/consteval28.C new file mode 100644 index 00000000000..293a6be2fc5 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/consteval28.C @@ -0,0 +1,10 @@ +// { dg-do compile { target c++20 } } + +struct empty { }; + +consteval void f(empty) { } + +template +void g(empty e) { + f(e); +} diff --git a/gcc/tree.cc b/gcc/tree.cc index c4b36619e6a..9d445b2740f 100644 --- a/gcc/tree.cc +++ b/gcc/tree.cc @@ -10492,7 +10492,7 @@ build_call_array_loc (location_t loc, tree return_type, tree fn, /* Like build_call_array, but takes a vec. */ tree -build_call_vec (tree return_type, tree fn, vec *args) +build_call_vec (tree return_type, tree fn, const vec *args) { tree ret, t; unsigned int ix; diff --git a/gcc/tree.h b/gcc/tree.h index 30bc53c2996..4c01d94244e 100644 --- a/gcc/tree.h +++ b/gcc/tree.h @@ -4589,7 +4589,7 @@ extern tree build_call_valist (tree, tree, int, va_list); #define build_call_array(T1,T2,N,T3)\ build_call_array_loc (UNKNOWN_LOCATION, T1, T2, N, T3) extern tree build_call_array_loc (location_t, tree, tree, int, const tree *); -extern tree build_call_vec (tree, tree, vec *); +extern tree build_call_vec (tree, tree, const vec *); extern tree build_call_expr_loc_array (location_t, tree, int, tree *); extern tree build_call_expr_loc_vec (location_t, tree, vec *); extern tree build_call_expr_loc (location_t, tree, int, ...); -- 2.35.0