qbittorrent @4.5.1: build failure, undefined symbols for std::filesystem on 10.14

[contextnerror]

qBittorrent fails to build on Mojave. Says something about undefined symbols for architecture x86_64.
macOS 10.14.6 18G9323 x86_64
Command Line Tools 10.3.0.0.1.1562985497
Log file is attached.

[contextnerror]

Sorry, I forgot to compress that before I uploaded it.

[i0ntempest]

I'm already aware but couldn't figure it out. It's related to C++ standards and the filesystem library. Need help from someone who knows C++.

[kencu (Ken)]

It's using std::filesystem but not finding the symbols for it in the system libc++.dylib to link against:

:info:build   "std::__1::__fs::filesystem::__status(std::__1::__fs::filesystem::path const&, std::__1::error_code*)", referenced from:
:info:build       Utils::Fs::isRegularFile(Path const&) in libqbt_base.a(fs.cpp.o)

because std::filesystem was not compiled into the system libc++.dylib until macOS 10.15.

​https://github.com/llvm/llvm-project/blob/997dc7e00f49663b60a78e18df1dfecdf62a4172/libcxx/include/__availability#L220

To get around this (ie to provide std::filesystem on older systems before 10.15) we have various options.

1. We can use the macports-libcxx port, which provides a newer libc++ to link against. This is very easy to do (it's an option in legacysupport) and often works, but there can sometimes be a hiccup mixing the newer libc++.dylib and the system libc++.dylib, so you have to do a bit of testing to make sure things work as expected.
2. You might be able to tell the software not to use std::filesystem somehow -- force off the detection code, if there is any, turn it off with a configure argument, etc.
3. Or we can find another way to provide the filesystem objects to the build -- older clang versions did have libfilesystem in a separate library that we could somehow make available to current clang versions to use.
4. Finally, there are a few options where std::filesystem is replaced with some other port, like this port:

ghc-filesystem @1.5.12 (devel)
    An implementation of C++17 std::filesystem.

which despite the name has nothing to do with ghc haskell (in this case, ghc are the author's initials). This port is said to reproduce std::filesystem quite accurately, and perhaps we might find a way to use this successfully on the other systems, ideally without too much actual patching. I haven't tried to do that as yet.

[i0ntempest]

In 3fe755327bbec563fcb40ded3dcd950d4c06fb1b/macports-ports (master):

qBittorrent: 4.5.2, enable legacysupport

Closes: #66956

[i0ntempest]

Thanks for the pointers, an attempt has been made to fix this, using macports-libcxx.

[contextnerror]

Build is still failing at the moment, but I don't know if the issue is related. Should this be its own ticket?

[contextnerror]

Second build failure log

[i0ntempest]

That's another error: error: no member named 'toggleVisibility' in 'MainWindow' Seen it before and I think it's qt-related. Try qbittorrent-qt5 port.

[contextnerror]

Unlike the standard port, the qt5 version is still giving the original std::filesystem error. Not sure why that is.

[i0ntempest]

Your log shows 4.5.1 which is before I added the fix to the qt5 port. Please do a selfupdate and try again.

[contextnerror]

Yeah, that one was my mistake. Now it's giving errors about not being able to find "filesystem" instead:

:info:build In file included from app/cmdoptions.cpp:31:
:info:build In file included from app/cmdoptions.h:39:
:info:build ./base/path.h:32:10: fatal error: 'filesystem' file not found
:info:build #include <filesystem>
:info:build          ^~~~~~~~~~~~`

[i0ntempest]

Try changing the compiler blacklist at line 39 to: compiler.blacklist-append *gcc-3.* *gcc-4.* *gcc-5.* *gcc-6.* *gcc-7.* {clang < 1100} and building again. You can get to the portfile using port edit qbittorrent-qt5.

[contextnerror]

Doing that seems to have brought me full circle, since it's failing due to undefined symbols again. But I think it's gotten further than before.

[i0ntempest]

Looks like legacysupport magic doesn't work for the qt5 port because it's using qmake (EDIT: yes it worked - stupid mistake by me), and I'll need to manually add the variables in to point it to the new libcxx. I don't have libcxx port since I'm running the newest OS, can you please post the output of port content libcxx?

[contextnerror]

Port libcxx contains: /opt/local/share/doc/libcxx/README.txt

Said text file has the following message:

libcxx is an empty port on this OS version because the functionality is already provided by the OS.

I'm assuming this isn't the info you wanted.

[i0ntempest]

What about macports-libcxx?

[contextnerror]

Output of port content macports-libcxx, for version 11.1.0

[i0ntempest]

Please try the portfile here: ​https://github.com/macports/macports-ports/pull/17845 and see if you get a successful build.

[contextnerror]

Failed pretty early on due to 'filesystem' file not found again.

[i0ntempest]

Made some changes to the PR, please get a new portfile and try again.

[contextnerror]

I got the error: no member named 'toggleVisibility' in 'MainWindow' error again. So I guess using the qt5 port didn't help with that after all.

[i0ntempest]

Well, in that case the newest qt supported on your OS just isn't enough to build it. This affects 4.3.2 on macOS 10.12 as well. See ​https://github.com/qbittorrent/qBittorrent/discussions/17326 for the question I posted that never got an answer.

[contextnerror]

It does look like you're right, based on comment:51:ticket:62441. I've voted up your question on github, but I won't be holding my breath for an answer.

I do appreciate all the time you've put in trying to get this to work, though.