Hi, Now that the -Woverloaded-virtual=1 is enabled by default with -Wall, the following code raises warning while I think it should not (for the specific case of conversion operators): #include <iostream> struct A { virtual operator int() { return 42; } virtual operator char() = 0; }; struct B : public A { operator char() override { return 'A'; } }; int main() { B b; std::cout << static_cast<int>(b) << std::endl; // int conversion was not hiden, contrary to what -Woverloaded-virtual claims std::cout << static_cast<char>(b) << std::endl; } Godbolt link: https://godbolt.org/z/4Wb9rxbMP Compiled with -Wall, it raises this warning: <source>:5:13: warning: 'virtual A::operator int()' was hidden [-Woverloaded-virtual=] 5 | virtual operator int() { return 42; } | ^~~~~~~~ <built-in>: note: by 'operator' ASM generation compiler returned: 0 <source>:5:13: warning: 'virtual A::operator int()' was hidden [-Woverloaded-virtual=] 5 | virtual operator int() { return 42; } | ^~~~~~~~ <built-in>: note: by 'operator' Execution build compiler returned: 0 Program returned: 0 42 A I have hit this issue in a real code base, while migrating to gcc 13. Cheers, Romain
Confirmed. GCC 7.5 didn't warn with -Woverloaded-virtual but GCC 8 does. Maybe introduced by r8-2977-g940ab2e08e2414 .
GCC 10 branch is being closed.
The testcase with -Werror=overloaded-virtual started failing with commit r8-2669-gbff8b385e997a8 (Nathan Sidwell: Conversion operators have a special name).
GCC 11 branch is being closed.
Working on this one.
The master branch has been updated by Simon Martin <simartin@gcc.gnu.org>: https://gcc.gnu.org/g:60163c85730e6b7c566e219222403ac87ddbbddd commit r15-4282-g60163c85730e6b7c566e219222403ac87ddbbddd Author: Simon Martin <simon@nasilyan.com> Date: Fri Oct 11 10:16:26 2024 +0200 c++: Fix overeager Woverloaded-virtual with conversion operators [PR109918] We currently emit an incorrect -Woverloaded-virtual warning upon the following test case === cut here === struct A { virtual operator int() { return 42; } virtual operator char() = 0; }; struct B : public A { operator char() { return 'A'; } }; === cut here === The problem is that when iterating over ovl_range (fns), warn_hidden gets confused by the conversion operator marker, concludes that seen_non_override is true and therefore emits a warning for all conversion operators in A that do not convert to char, even if -Woverloaded-virtual is 1 (e.g. with -Wall, the case reported). A second set of problems is highlighted when -Woverloaded-virtual is 2. First, with the same test case, since base_fndecls contains all conversion operators in A (except the one to char, that's been removed when iterating over ovl_range (fns)), we emit a spurious warning for the conversion operator to int, even though it's unrelated. Second, in case there are several conversion operators with different cv-qualifiers to the same type in A, we rightfully emit a warning, however the note uses the location of the conversion operator marker instead of the right one; location_of should go over conv_op_marker. This patch fixes all these by explicitly keeping track of (1) base methods that are overriden, as well as (2) base methods that are hidden but not overriden (and by what), and warning about methods that are in (2) but not (1). It also ignores non virtual base methods, per "definition" of -Woverloaded-virtual. PR c++/109918 gcc/cp/ChangeLog: * class.cc (warn_hidden): Keep track of overloaded and of hidden base methods. Mention the actual hiding function in the warning, not the first overload. * error.cc (location_of): Skip over conv_op_marker. gcc/testsuite/ChangeLog: * g++.dg/warn/Woverloaded-virt1.C: Check that no warning is emitted for non virtual base methods. * g++.dg/warn/Woverloaded-virt5.C: New test. * g++.dg/warn/Woverloaded-virt6.C: New test. * g++.dg/warn/Woverloaded-virt7.C: New test. * g++.dg/warn/Woverloaded-virt8.C: New test. * g++.dg/warn/Woverloaded-virt9.C: New test.
Fixed on trunk.
As this is a regression, it would usually be fixed on all open branches. Was closing it without backports intentional?
This breaks building the rust compiler. In file included from ../../gcc/rust/typecheck/rust-tyty.h:28, from ../../gcc/rust/backend/rust-mangle.h:21, from ../../gcc/rust/backend/rust-mangle.cc:19: ../../gcc/rust/typecheck/rust-tyty-subst.h:408:21: error: 'virtual Rust::TyTy::BaseType* Rust::TyTy::SubstitutionRef::handle_substitions(Rust::TyTy::Substitut\ ionArgumentMappings&)' was hidden [-Werror=overloaded-virtual=] 408 | virtual BaseType *handle_substitions (SubstitutionArgumentMappings &mappings) | ^~~~~~~~~~~~~~~~~~ ../../gcc/rust/typecheck/rust-tyty.h:761:3: note: by 'virtual Rust::TyTy::ADTType* Rust::TyTy::ADTType::handle_substitions(Rust::TyTy::SubstitutionArgumentMappings&)' 761 | handle_substitions (SubstitutionArgumentMappings &mappings) override final; | ^~~~~~~~~~~~~~~~~~ ../../gcc/rust/typecheck/rust-tyty-subst.h:408:21: error: 'virtual Rust::TyTy::BaseType* Rust::TyTy::SubstitutionRef::handle_substitions(Rust::TyTy::SubstitutionArgumentMappings&)' was hidden [-Werror=overloaded-virtual=] 408 | virtual BaseType *handle_substitions (SubstitutionArgumentMappings &mappings) | ^~~~~~~~~~~~~~~~~~ ../../gcc/rust/typecheck/rust-tyty.h:873:3: note: by 'virtual Rust::TyTy::FnType* Rust::TyTy::FnType::handle_substitions(Rust::TyTy::SubstitutionArgumentMappings&)' 873 | handle_substitions (SubstitutionArgumentMappings &mappings) override final; | ^~~~~~~~~~~~~~~~~~ ../../gcc/rust/typecheck/rust-tyty-subst.h:408:21: error: 'virtual Rust::TyTy::BaseType* Rust::TyTy::SubstitutionRef::handle_substitions(Rust::TyTy::SubstitutionArgumentMappings&)' was hidden [-Werror=overloaded-virtual=] 408 | virtual BaseType *handle_substitions (SubstitutionArgumentMappings &mappings) | ^~~~~~~~~~~~~~~~~~ ../../gcc/rust/typecheck/rust-tyty.h:1033:3: note: by 'virtual Rust::TyTy::ClosureType* Rust::TyTy::ClosureType::handle_substitions(Rust::TyTy::SubstitutionArgumentMappings&)' 1033 | handle_substitions (SubstitutionArgumentMappings &mappings) override final; | ^~~~~~~~~~~~~~~~~~ ../../gcc/rust/typecheck/rust-tyty-subst.h:408:21: error: 'virtual Rust::TyTy::BaseType* Rust::TyTy::SubstitutionRef::handle_substitions(Rust::TyTy::SubstitutionArgumentMappings&)' was hidden [-Werror=overloaded-virtual=] 408 | virtual BaseType *handle_substitions (SubstitutionArgumentMappings &mappings) | ^~~~~~~~~~~~~~~~~~ ../../gcc/rust/typecheck/rust-tyty.h:1576:3: note: by 'virtual Rust::TyTy::ProjectionType* Rust::TyTy::ProjectionType::handle_substitions(Rust::TyTy::SubstitutionArgumentMappings&)' 1576 | handle_substitions (SubstitutionArgumentMappings &mappings) override final; | ^~~~~~~~~~~~~~~~~~ cc1plus: all warnings being treated as errors make[3]: *** [../../gcc/rust/Make-lang.in:433: rust/rust-mangle.o] Error 1
(In reply to Andreas Schwab from comment #9) > This breaks building the rust compiler. > That's PR117114.
Reopening since this broke the rust build and I don't have an immediate fix.
Revert done via r15-4301-ga4eec6c712ec16
Patch submitted in https://gcc.gnu.org/pipermail/gcc-patches/2024-October/665650.html
The master branch has been updated by Simon Martin <simartin@gcc.gnu.org>: https://gcc.gnu.org/g:d346af2af88caf1e21a5cc1f0afa33596198fb60 commit r15-7350-gd346af2af88caf1e21a5cc1f0afa33596198fb60 Author: Simon Martin <simon@nasilyan.com> Date: Tue Feb 4 10:58:17 2025 +0100 c++: Fix overeager Woverloaded-virtual with conversion operators [PR109918] We currently emit an incorrect -Woverloaded-virtual warning upon the following test case === cut here === struct A { virtual operator int() { return 42; } virtual operator char() = 0; }; struct B : public A { operator char() { return 'A'; } }; === cut here === The problem is that when iterating over ovl_range (fns), warn_hidden gets confused by the conversion operator marker, concludes that seen_non_override is true and therefore emits a warning for all conversion operators in A that do not convert to char, even if -Woverloaded-virtual is 1 (e.g. with -Wall, the case reported). A second set of problems is highlighted when -Woverloaded-virtual is 2. First, with the same test case, since base_fndecls contains all conversion operators in A (except the one to char, that's been removed when iterating over ovl_range (fns)), we emit a spurious warning for the conversion operator to int, even though it's unrelated. Second, in case there are several conversion operators with different cv-qualifiers to the same type in A, we rightfully emit a warning, however the note uses the location of the conversion operator marker instead of the right one; location_of should go over conv_op_marker. This patch fixes all these by explicitly keeping track of (1) base methods that are overriden, as well as (2) base methods that are hidden but not overriden (and by what), and warning about methods that are in (2) but not (1). It also ignores non virtual base methods, per "definition" of -Woverloaded-virtual. Co-authored-by: Jason Merrill <jason@redhat.com> PR c++/117114 PR c++/109918 gcc/cp/ChangeLog: * class.cc (warn_hidden): Keep track of overloaded and of hidden base methods. * error.cc (location_of): Skip over conv_op_marker. gcc/testsuite/ChangeLog: * g++.dg/warn/Woverloaded-virt1.C: Check that no warning is emitted for non virtual base methods. * g++.dg/warn/Woverloaded-virt10.C: New test. * g++.dg/warn/Woverloaded-virt11.C: New test. * g++.dg/warn/Woverloaded-virt12.C: New test. * g++.dg/warn/Woverloaded-virt13.C: New test. * g++.dg/warn/Woverloaded-virt5.C: New test. * g++.dg/warn/Woverloaded-virt6.C: New test. * g++.dg/warn/Woverloaded-virt7.C: New test. * g++.dg/warn/Woverloaded-virt8.C: New test. * g++.dg/warn/Woverloaded-virt9.C: New test.
Fixed in GCC 15.