ignition utils 1.2.0 doesn't build with ign-cmake 2.10.0 and with clang-6.0 compiler

[gazebosim]

ignition utils 1.2.0 doesn't build with ign-cmake 2.10.0 and with clang-6.0 compiler

[mjcarroll]

Here is a very minimal reproduction excluding everything ignition-related: https://github.com/mjcarroll/clang6-inline-namespace

[mjcarroll]

Hope this is not going to be a problem for other downstream dependencies of ignition-fortress ?

This is a pretty common pattern throughout the stack, so I would expect that clang-6 may have issues on all the other packages.

I think at the very least, we will make a note indicating that there are known issues with that compiler.

[mjcarroll]

Thanks for reporting, I can reproduce on Ubuntu focal with clang-6.0.

My suspicion is that there is something incorrect with how name mangling works with inline namespace in clang-6.

When built with clang-6 the functions don't get the v1 namespace:

$ nm -a lib/libignition-utils1.so | c++filt | grep ignition::utils
00000000000011d0 T ignition::utils::env(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&, bool)
0000000000001290 T ignition::utils::setenv(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)
00000000000012b0 T ignition::utils::unsetenv(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)

Versus building with something newer (clang-12 in this case):

00000000000011d0 T ignition::utils::v1::env(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&, bool)
0000000000001280 T ignition::utils::v1::setenv(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)
00000000000012a0 T ignition::utils::v1::unsetenv(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)

The inline namespace pattern is pretty heavily used throughout the ignition stack, so if clang-6 doesn't correctly support it (or a workaround), we will likely have to note it as unsupported. I can't find any evidence that this wouldn't be supported as clang-6 should fully support the c++17 standard.

[ggulgulia]

@mjcarroll thanks for updates and moving the issue to development. Hope to see this working soon. Also I cannot edit the labels, if it is valid, then can you add edifice lable to the issue ?

[mjcarroll]

Hope to see this working soon

After chatting with some colleagues, I'm inclined to say it's either a compiler bug or a weird edge case. I don't know that there will be anything on our side that we can do to handle it.

In the meantime, is there any way that you can use a newer compiler? I see that clang-7 is available via bionic-updates: https://packages.ubuntu.com/bionic-updates/clang-7

[ggulgulia]

yes we can work with other compilers. The compilation error was detected when CI did an automatic build of the conan recipe with multiple compilers and clang-6.0 was one of them. We need only gcc compiler at the moment. To create the conan recipe, we have to simply disable ign-uitls 1.2.0 from the recipe. Hope this is not going to be a problem for other downstream dependencies of ignition-fortress ?

[azeey]

@ggulgulia Can you check if #39 fixes the problem for you?