From: Patrick Palka Date: Mon, 18 Sep 2023 18:41:05 +0000 (-0400) Subject: c++: always check arity before deduction X-Git-Tag: basepoints/gcc-15~6030 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=155178ccb5f5bc89dcc8261ae1b64bc2fbfdbd45;p=thirdparty%2Fgcc.git c++: always check arity before deduction This simple patch extends the r12-3271-gf1e73199569287 optimization to happen for 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 uniformly pruned overloads according to arity early. This incidentally causes us to accept one reduced testcase from PR c++/84075, but the underlying issue there remains at large. As a nice side effect, this change causes 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 along the lines of 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. --- diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc index 399345307ea3..2bbaeee039d4 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 440bea5b2f75..bac3b64ad7e8 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 1a99e22c5cb2..22b19ef6c1a0 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 902684059a80..932c13bde301 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 000000000000..202549a7eab2 --- /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 94c19be56a29..d8ca5aa66ebb 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 000000000000..9d68b9e8bbca --- /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 specialized, + // which would have resulted in a hard error +}