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[75.172.69.110]) by smtp.gmail.com with ESMTPSA id p13-20020a05620a22ad00b007204305dee4sm4661350qkh.19.2023.02.04.17.41.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 04 Feb 2023 17:41:08 -0800 (PST) Message-ID: <0e0bc838-466e-20ea-4523-a075be14ef76@redhat.com> Date: Sat, 4 Feb 2023 17:41:07 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [PATCH] c++: equivalence of non-dependent calls [PR107461] To: Patrick Palka Cc: gcc-patches@gcc.gnu.org References: <20230204203126.782976-1-ppalka@redhat.com> <3f14f800-4b00-9215-c249-1c7f19d43560@redhat.com> <9b958e6f-6f8b-9183-5277-39f83871dd9d@idea> From: Jason Merrill In-Reply-To: <9b958e6f-6f8b-9183-5277-39f83871dd9d@idea> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-12.8 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,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 List-Id: On 2/4/23 20:08, Patrick Palka wrote: > On Sat, 4 Feb 2023, Jason Merrill wrote: > >> On 2/4/23 15:31, Patrick Palka wrote: >>> After r13-5684-g59e0376f607805 the (pruned) callee of a non-dependent >>> CALL_EXPR is a bare FUNCTION_DECL rather than ADDR_EXPR of FUNCTION_DECL. >>> This innocent change revealed that cp_tree_equal doesn't first check >>> dependentness of a CALL_EXPR before treating the callee as a dependent >>> name, which manifests as us incorrectly accepting the first two >>> testcases below and rejecting the third: >>> >>> * In the first testcase, cp_tree_equal incorrectly returns true for >>> the two non-dependent CALL_EXPRs f(0) and f(0) (whose CALL_EXPR_FN >>> are different FUNCTION_DECLs) and so we treat #2 as a redeclaration >>> of #1. >>> >>> * Same issue in the second testcase, for f() and f(). >>> >>> * In the third testcase, cp_tree_equal incorrectly returns true for >>> f() and f() which causes us to conflate the two >>> dependent specializations A()(U()))> and >>> A()(U()))>, leading to a bogus error. >>> >>> This patch fixes this by making called_fns_equal treat two callees as >>> dependent names only if the CALL_EXPRs in question are dependent. >>> >>> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for >>> trunk/12? Patch generated with -w to ignore noisy whitespace changes. >>> >>> PR c++/107461 >>> >>> gcc/cp/ChangeLog: >>> >>> * pt.cc (iterative_hash_template_arg) : Treat >>> the callee as a dependent name only if the CALL_EXPR is >>> dependent. >>> * tree.cc (called_fns_equal): Take two CALL_EXPRs instead of >>> CALL_EXPR_FNs thereof. As above. >>> (cp_tree_equal) : Adjust call to called_fns_equal. >>> >>> gcc/testsuite/ChangeLog: >>> >>> * g++.dg/cpp0x/overload5.C: New test. >>> * g++.dg/cpp0x/overload5a.C: New test. >>> * g++.dg/cpp0x/overload6.C: New test. >>> --- >>> gcc/cp/pt.cc | 1 + >>> gcc/cp/tree.cc | 33 ++++++++++++++----------- >>> gcc/testsuite/g++.dg/cpp0x/overload5.C | 12 +++++++++ >>> gcc/testsuite/g++.dg/cpp0x/overload5a.C | 10 ++++++++ >>> gcc/testsuite/g++.dg/cpp0x/overload6.C | 16 ++++++++++++ >>> 5 files changed, 58 insertions(+), 14 deletions(-) >>> create mode 100644 gcc/testsuite/g++.dg/cpp0x/overload5.C >>> create mode 100644 gcc/testsuite/g++.dg/cpp0x/overload5a.C >>> create mode 100644 gcc/testsuite/g++.dg/cpp0x/overload6.C >>> >>> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc >>> index 255332dc0c1..c9360240cd2 100644 >>> --- a/gcc/cp/pt.cc >>> +++ b/gcc/cp/pt.cc >>> @@ -1841,6 +1841,7 @@ iterative_hash_template_arg (tree arg, hashval_t val) >>> case CALL_EXPR: >>> { >>> tree fn = CALL_EXPR_FN (arg); >>> + if (TREE_TYPE (arg) == NULL_TREE) >> >> How about changing dependent_name to take the CALL_EXPR rather than the >> CALL_EXPR_FN? That would mean some changes to write_expression to move the >> dependent_name handling into the CALL_EXPR handling, but that doesn't seem >> like a bad thing. Other callers seem like a trivial change. > > Indeed changing dependent_name seems best, but I'm worried about such a > refactoring to write_expression causing unintended mangling changes at > this stage. Because it seems the CALL_EXPR case of write_expression > isn't the user of the dependent_name branch of write_expression, at > least according to the following patch which causes us to ICE on > mangle{37,57,58,76}.C: Yeah, I tried the same thing. Maybe for GCC 13 better to add a new function rather than change the current one. > diff --git a/gcc/cp/mangle.cc b/gcc/cp/mangle.cc > index f2cda3be2cf..700857f8f3c 100644 > --- a/gcc/cp/mangle.cc > +++ b/gcc/cp/mangle.cc > @@ -3450,6 +3450,7 @@ write_expression (tree expr) > } > else if (dependent_name (expr)) > { > + gcc_unreachable (); > tree name = dependent_name (expr); > if (IDENTIFIER_ANY_OP_P (name)) > { > @@ -3554,7 +3555,19 @@ write_expression (tree expr) > && type_dependent_expression_p_push (expr)) > fn = OVL_NAME (fn); > > - write_expression (fn); > + if (tree name = dependent_name (fn)) > + { > + if (IDENTIFIER_ANY_OP_P (name)) > + { > + if (abi_version_at_least (16)) > + write_string ("on"); > + if (abi_warn_or_compat_version_crosses (16)) > + G.need_abi_warning = 1; > + } > + write_unqualified_id (name); > + } > + else > + write_expression (fn); > } > > for (i = 0; i < call_expr_nargs (expr); ++i) > > And since the CALL_EXPR case of write_expression looks through an > ADDR_EXPR callee before recursing, IIUC the refactoring would need to > make dependent_name look through an ADDR_EXPR callee as well, which > seems like a desirable/correct change but I'm worried that might have > unintended consequences as well. > >> >>> if (tree name = dependent_name (fn)) >>> { >>> if (TREE_CODE (fn) == TEMPLATE_ID_EXPR) >>> diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc >>> index c1da868732b..3a57e71b76e 100644 >>> --- a/gcc/cp/tree.cc >>> +++ b/gcc/cp/tree.cc >>> @@ -3870,16 +3870,21 @@ decl_internal_context_p (const_tree decl) >>> return !TREE_PUBLIC (decl); >>> } >>> -/* Subroutine of cp_tree_equal: t1 and t2 are the CALL_EXPR_FNs of two >>> - CALL_EXPRS. Return whether they are equivalent. */ >>> +/* Subroutine of cp_tree_equal: t1 and t2 are two CALL_EXPRs. >>> + Return whether their CALL_EXPR_FNs are equivalent. */ >>> static bool >>> called_fns_equal (tree t1, tree t2) >>> +{ >>> + tree fn1 = CALL_EXPR_FN (t1); >>> + tree fn2 = CALL_EXPR_FN (t2); >>> + if (TREE_TYPE (t1) == NULL_TREE >>> + && TREE_TYPE (t2) == NULL_TREE) >>> { >>> /* Core 1321: dependent names are equivalent even if the overload >>> sets >>> are different. But do compare explicit template arguments. */ >>> - tree name1 = dependent_name (t1); >>> - tree name2 = dependent_name (t2); >>> + tree name1 = dependent_name (fn1); >>> + tree name2 = dependent_name (fn2); >>> if (name1 || name2) >>> { >>> tree targs1 = NULL_TREE, targs2 = NULL_TREE; >>> @@ -3891,19 +3896,19 @@ called_fns_equal (tree t1, tree t2) >>> of whether the function was named with a qualified- or >>> unqualified-id. >>> Until that's fixed, check that we aren't looking at overload sets >>> from >>> different scopes. */ >>> - if (is_overloaded_fn (t1) && is_overloaded_fn (t2) >>> - && (DECL_CONTEXT (get_first_fn (t1)) >>> - != DECL_CONTEXT (get_first_fn (t2)))) >>> + if (is_overloaded_fn (fn1) && is_overloaded_fn (fn2) >>> + && (DECL_CONTEXT (get_first_fn (fn1)) >>> + != DECL_CONTEXT (get_first_fn (fn2)))) >>> return false; >>> - if (TREE_CODE (t1) == TEMPLATE_ID_EXPR) >>> - targs1 = TREE_OPERAND (t1, 1); >>> - if (TREE_CODE (t2) == TEMPLATE_ID_EXPR) >>> - targs2 = TREE_OPERAND (t2, 1); >>> + if (TREE_CODE (fn1) == TEMPLATE_ID_EXPR) >>> + targs1 = TREE_OPERAND (fn1, 1); >>> + if (TREE_CODE (fn2) == TEMPLATE_ID_EXPR) >>> + targs2 = TREE_OPERAND (fn2, 1); >>> return cp_tree_equal (targs1, targs2); >>> } >>> - else >>> - return cp_tree_equal (t1, t2); >>> + } >>> + return cp_tree_equal (fn1, fn2); >>> } >>> bool comparing_override_contracts; >>> @@ -4037,7 +4042,7 @@ cp_tree_equal (tree t1, tree t2) >>> if (KOENIG_LOOKUP_P (t1) != KOENIG_LOOKUP_P (t2)) >>> return false; >>> - if (!called_fns_equal (CALL_EXPR_FN (t1), CALL_EXPR_FN (t2))) >>> + if (!called_fns_equal (t1, t2)) >>> return false; >>> call_expr_arg_iterator iter1, iter2; >>> diff --git a/gcc/testsuite/g++.dg/cpp0x/overload5.C >>> b/gcc/testsuite/g++.dg/cpp0x/overload5.C >>> new file mode 100644 >>> index 00000000000..e05b1594f51 >>> --- /dev/null >>> +++ b/gcc/testsuite/g++.dg/cpp0x/overload5.C >>> @@ -0,0 +1,12 @@ >>> +// PR c++/107461 >>> +// { dg-do compile { target c++11 } } >>> + >>> +int f(...); >>> +template decltype(T() + f(0)) g(); // #1 >>> + >>> +char f(int); >>> +template decltype(T() + f(0)) g(); // #2, distinct from #1 >>> + >>> +int main() { >>> + g(); // { dg-error "ambiguous" } >>> +} >>> diff --git a/gcc/testsuite/g++.dg/cpp0x/overload5a.C >>> b/gcc/testsuite/g++.dg/cpp0x/overload5a.C >>> new file mode 100644 >>> index 00000000000..037114f199c >>> --- /dev/null >>> +++ b/gcc/testsuite/g++.dg/cpp0x/overload5a.C >>> @@ -0,0 +1,10 @@ >>> +// PR c++/107461 >>> +// { dg-do compile { target c++11 } } >>> + >>> +template T f(); >>> +template decltype(T() + f()) g(); // #1 >>> +template decltype(T() + f()) g(); // #2, distinct from #1 >>> + >>> +int main() { >>> + g(); // { dg-error "ambiguous" } >>> +} >>> diff --git a/gcc/testsuite/g++.dg/cpp0x/overload6.C >>> b/gcc/testsuite/g++.dg/cpp0x/overload6.C >>> new file mode 100644 >>> index 00000000000..1fbee0501de >>> --- /dev/null >>> +++ b/gcc/testsuite/g++.dg/cpp0x/overload6.C >>> @@ -0,0 +1,16 @@ >>> +// PR c++/107461 >>> +// { dg-do compile { target c++11 } } >>> + >>> +template T f(); >>> + >>> +template struct A { }; >>> + >>> +template struct B { >>> + template()(U()))>> >>> + static void g(U); >>> +}; >>> + >>> +int main() { >>> + B b; >>> + B::g(0); // { dg-bogus "no match" } >>> +} >> >> >