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[69.118.112.187]) by smtp.gmail.com with ESMTPSA id g7-20020ad45107000000b00655e2005350sm2568441qvp.9.2023.09.12.17.33.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Sep 2023 17:33:23 -0700 (PDT) To: gcc-patches@gcc.gnu.org Cc: jason@redhat.com, Patrick Palka Subject: [PATCH] c++: always check arity before deduction Date: Tue, 12 Sep 2023 20:33:20 -0400 Message-ID: <20230913003320.1896552-1-ppalka@redhat.com> X-Mailer: git-send-email 2.42.0.158.g94e83dcf5b MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-13.6 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_NONE, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Patrick Palka via Gcc-patches From: Patrick Palka Reply-To: Patrick Palka Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org Sender: "Gcc-patches" Bootstrpaped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk? -- >8 -- This simple patch extends the r12-3271-gf1e73199569287 optimization to apply to deduction without explicit template arguments as well. The motivation for this is to accept testcases such as conv20.C and ttp40.C below, which don't use explicit template arguments but for which unnecessary template instantiation during deduction could be avoided if we pruned overloads according to arity early in this case as well. This incidentally causes us to accept one reduced testcase from PR c++/84075, but the underlying issue there still remains unfixed. As an added bonus, this change ends up causing the "candidate expects N argument(s)" note during overload resolution failure to point to the template candidate instead of the call site, which seems like an improvement similar to r14-309-g14e881eb030509. gcc/cp/ChangeLog: * call.cc (add_template_candidate_real): Check arity even when there are no explicit template arguments. Combine the two adjacent '!obj' tests into one. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/vt-57397-1.C: Expect "candidate expects ... N argument(s)" at the declaration site instead of the call site. * g++.dg/cpp0x/vt-57397-2.C: Likewise. * g++.dg/overload/template5.C: Likewise. * g++.dg/template/local6.C: Likewise. * g++.dg/template/conv20.C: New test. * g++.dg/template/ttp40.C: New test. --- gcc/cp/call.cc | 14 ++++++------- gcc/testsuite/g++.dg/cpp0x/vt-57397-1.C | 6 +++--- gcc/testsuite/g++.dg/cpp0x/vt-57397-2.C | 6 +++--- gcc/testsuite/g++.dg/overload/template5.C | 4 ++-- gcc/testsuite/g++.dg/template/conv20.C | 17 +++++++++++++++ gcc/testsuite/g++.dg/template/local6.C | 4 ++-- gcc/testsuite/g++.dg/template/ttp40.C | 25 +++++++++++++++++++++++ 7 files changed, 58 insertions(+), 18 deletions(-) create mode 100644 gcc/testsuite/g++.dg/template/conv20.C create mode 100644 gcc/testsuite/g++.dg/template/ttp40.C diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc index 399345307ea..2bbaeee039d 100644 --- a/gcc/cp/call.cc +++ b/gcc/cp/call.cc @@ -3535,13 +3535,13 @@ add_template_candidate_real (struct z_candidate **candidates, tree tmpl, } gcc_assert (ia == nargs_without_in_chrg); - if (!obj && explicit_targs) + if (!obj) { /* Check that there's no obvious arity mismatch before proceeding with deduction. This avoids substituting explicit template arguments - into the template (which could result in an error outside the - immediate context) when the resulting candidate would be unviable - anyway. */ + into the template or e.g. derived-to-base parm/arg unification + (which could result in an error outside the immediate context) when + the resulting candidate would be unviable anyway. */ int min_arity = 0, max_arity = 0; tree parms = TYPE_ARG_TYPES (TREE_TYPE (tmpl)); parms = skip_artificial_parms_for (tmpl, parms); @@ -3571,11 +3571,7 @@ add_template_candidate_real (struct z_candidate **candidates, tree tmpl, reason = arity_rejection (NULL_TREE, max_arity, ia); goto fail; } - } - errs = errorcount+sorrycount; - if (!obj) - { convs = alloc_conversions (nargs); if (shortcut_bad_convs @@ -3602,6 +3598,8 @@ add_template_candidate_real (struct z_candidate **candidates, tree tmpl, } } } + + errs = errorcount+sorrycount; fn = fn_type_unification (tmpl, explicit_targs, targs, args_without_in_chrg, nargs_without_in_chrg, diff --git a/gcc/testsuite/g++.dg/cpp0x/vt-57397-1.C b/gcc/testsuite/g++.dg/cpp0x/vt-57397-1.C index 440bea5b2f7..bac3b64ad7e 100644 --- a/gcc/testsuite/g++.dg/cpp0x/vt-57397-1.C +++ b/gcc/testsuite/g++.dg/cpp0x/vt-57397-1.C @@ -3,20 +3,20 @@ template void foo(T1, Tn...); +// { dg-message "candidate expects at least 1 argument, 0 provided" "" { target *-*-* } .-1 } template void bar(T1, T2, Tn...); +// { dg-message "candidate expects at least 2 arguments, 0 provided" "" { target *-*-* } .-1 } +// { dg-message "candidate expects at least 2 arguments, 1 provided" "" { target *-*-* } .-2 } int main() { foo(); // { dg-error "no matching" } - // { dg-message "candidate expects at least 1 argument, 0 provided" "" { target *-*-* } .-1 } foo(1); foo(1, 2); bar(); // { dg-error "no matching" } - // { dg-message "candidate expects at least 2 arguments, 0 provided" "" { target *-*-* } .-1 } bar(1); // { dg-error "no matching" } - // { dg-message "candidate expects at least 2 arguments, 1 provided" "" { target *-*-* } .-1 } bar(1, 2); bar(1, 2, 3); } diff --git a/gcc/testsuite/g++.dg/cpp0x/vt-57397-2.C b/gcc/testsuite/g++.dg/cpp0x/vt-57397-2.C index 1a99e22c5cb..22b19ef6c1a 100644 --- a/gcc/testsuite/g++.dg/cpp0x/vt-57397-2.C +++ b/gcc/testsuite/g++.dg/cpp0x/vt-57397-2.C @@ -3,21 +3,21 @@ template void foo(T1, Tn..., Tm...); +// { dg-message "candidate expects at least 1 argument, 0 provided" "" { target *-*-* } .-1 } template void bar(T1, T2, Tn..., Tm...); +// { dg-message "candidate expects at least 2 arguments, 0 provided" "" { target *-*-* } .-1 } +// { dg-message "candidate expects at least 2 arguments, 1 provided" "" { target *-*-* } .-2 } int main() { foo(); // { dg-error "no matching" } - // { dg-message "candidate expects at least 1 argument, 0 provided" "" { target *-*-* } .-1 } foo(1); foo(1, 2); foo(1, 2, 3); bar(); // { dg-error "no matching" } - // { dg-message "candidate expects at least 2 arguments, 0 provided" "" { target *-*-* } .-1 } bar(1); // { dg-error "no matching" } - // { dg-message "candidate expects at least 2 arguments, 1 provided" "" { target *-*-* } .-1 } bar(1, 2); bar(1, 2, 3); bar(1, 2, 3, 4); diff --git a/gcc/testsuite/g++.dg/overload/template5.C b/gcc/testsuite/g++.dg/overload/template5.C index 902684059a8..932c13bde30 100644 --- a/gcc/testsuite/g++.dg/overload/template5.C +++ b/gcc/testsuite/g++.dg/overload/template5.C @@ -2,14 +2,14 @@ template int low(T a, T b, T c) { return a + b + c; } // { dg-message "template" } +// { dg-message "(candidate|3 arguments, 2 provided)" "" { target *-*-* } .-1 } template int high(T a, T b, T c) { return a + b + c; } // { dg-message "template" } +// { dg-message "(candidate|3 arguments, 4 provided)" "" { target *-*-* } .-1 } void test (void) { low (5, 6); // { dg-error "no matching function" } - // { dg-message "(candidate|3 arguments, 2 provided)" "" { target *-*-* } .-1 } high (5, 6, 7, 8); // { dg-error "no matching function" } - // { dg-message "(candidate|3 arguments, 4 provided)" "" { target *-*-* } .-1 } } diff --git a/gcc/testsuite/g++.dg/template/conv20.C b/gcc/testsuite/g++.dg/template/conv20.C new file mode 100644 index 00000000000..202549a7eab --- /dev/null +++ b/gcc/testsuite/g++.dg/template/conv20.C @@ -0,0 +1,17 @@ +// Verify we check arity early before deduction without explicit +// template arguments. + +template +struct A; + +template +struct B : A { }; + +template void f(A&, int); // #1 +template void f(B&); // #2 + +int main() { + extern B b; + ::f(b); // OK, deduction for #1 short-circuited and B not instantiated, + // which would have resulted in a hard error +} diff --git a/gcc/testsuite/g++.dg/template/local6.C b/gcc/testsuite/g++.dg/template/local6.C index 94c19be56a2..d8ca5aa66eb 100644 --- a/gcc/testsuite/g++.dg/template/local6.C +++ b/gcc/testsuite/g++.dg/template/local6.C @@ -1,11 +1,11 @@ template struct PCVector2 // { dg-message "note" } { - template PCVector2(const PCVector2 &cv) ; // { dg-message "note" } + template PCVector2(const PCVector2 &cv) ; // { dg-message "candidate:" } + // { dg-message "(candidate|expects 1 argument, 2 provided|cannot convert)" "candidate note" { target *-*-* } .-1 } PCVector2 operator- (const PCVector2 &ov) const { return PCVector2(ov.xFIELD, ov.yFIELD); // { dg-error "matching" } - // { dg-message "(candidate|expects 1 argument, 2 provided|cannot convert)" "candidate note" { target *-*-* } .-1 } } T xFIELD, yFIELD; diff --git a/gcc/testsuite/g++.dg/template/ttp40.C b/gcc/testsuite/g++.dg/template/ttp40.C new file mode 100644 index 00000000000..826eed86ed4 --- /dev/null +++ b/gcc/testsuite/g++.dg/template/ttp40.C @@ -0,0 +1,25 @@ +// Verify we check arity early before deduction without explicit +// template arguments. +// PR c++/84075 + +template +struct trait { + static const int value = T::value; // { dg-bogus "not a member of 'B'" } +}; + +template::value> +struct A { }; + +template +void f(A, int); // #1 + +struct B { }; + +template class TT> +void f(TT); // #2 + +int main() { + A a; + f(a, 0); // OK, deduction for #2 short-circuited and A not formed, + // which would have resulted in a hard error +}