A modern, delicious implementation of the Nix package manager, focused on correctness, usability, and growth — and committed to doing right by its community
https://lix.systems
jade
ac78c1dcd5
This is because a dynamic_cast<nix::RootArgs *> of a (n-e-j) MyArgs
returns nullptr even though MyArgs has virtual nix::RootArgs as a
parent.
class MyArgs : virtual public nix::MixEvalArgs,
virtual public nix::MixCommonArgs,
virtual nix::RootArgs { ... };
So this should work right?? But it does not. We found out that it's
caused by -fvisibility=hidden in n-e-j, but honestly this code was bad
anyway.
The trivial solution is to simply stop relying on RTTI working properly
here, which is probably better OO architecture anyway. However, I am not
100% confident *this* is sound, since we have this horrible hierarchy:
Args (defines getRoot)
/ | \
RootArgs MixCommonArgs MixEvalArgs
(overrides)
I am not confident that this is guaranteed to resolve from Args always
in the case of this override.
Assertion failed: (res), function getRoot, file src/libutil/args.cc, line 67.
6MyArgsProcess 60503 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = hit program assert
frame #4: 0x0000000100b1a41c liblixutil.dylib`nix::Args::processArgs(std::__1::list<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>> const&, bool) [inlined] nix::Args::getRoot(this=0x00000001000d0688) at args.cc:67:5 [opt]
64 std::cout << typeid(*p).name();
65
66 auto * res = dynamic_cast<RootArgs *>(p);
-> 67 assert(res);
68 return *res;
69 }
70
Target 0: (nix-eval-jobs) stopped.
(lldb) p this
(MyArgs *) 0x00000001000d0688
(lldb) p *this
(nix::Args) {
longFlags = size=180 { ... }
shortFlags = size=4 { ... }
expectedArgs = size=1 { ... }
processedArgs = size=0 {}
hiddenCategories = size=1 {
[0] = "Options to override configuration settings"
}
parent = nullptr
}
We also found that if we did this:
class [[gnu::visibility("default")]] RootArgs : virtual public Args
it would work properly (???!). This is of course, very strange, because
objdump -Ct output on liblixexpr.dylib is identical both with and
without it.
Possibly related: https://www.qt.io/blog/quality-assurance/one-way-dynamic_cast-across-library-boundaries-can-fail-and-how-to-fix-it
Fixes: lix-project/nix-eval-jobs#2
Change-Id:
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|---|---|---|
| .github | ||
| bench | ||
| clang-tidy | ||
| contrib | ||
| doc | ||
| lix-doc | ||
| maintainers | ||
| meson | ||
| misc | ||
| nix-support | ||
| perl | ||
| scripts | ||
| src | ||
| subprojects/aws_sdk | ||
| tests | ||
| .clang-format | ||
| .clang-tidy | ||
| .dir-locals.el | ||
| .editorconfig | ||
| .envrc | ||
| .gitignore | ||
| .version | ||
| boehmgc-coroutine-sp-fallback.diff | ||
| boehmgc-traceable_allocator-public.diff | ||
| CONTRIBUTING.md | ||
| COPYING | ||
| default.nix | ||
| docker.nix | ||
| flake.lock | ||
| flake.nix | ||
| justfile | ||
| meson.build | ||
| meson.options | ||
| package.nix | ||
| precompiled-headers.h | ||
| README.md | ||
| shell.nix | ||
| treefmt.toml | ||
Lix
Lix is an implementation of Nix, a powerful package management system for Linux and other Unix systems that makes package management reliable and reproducible.
Read more about us at https://lix.systems.
Installation
On Linux and macOS the easiest way to install Nix is to run the following shell command (as a user other than root):
$ curl -sSf -L https://install.lix.systems/lix | sh -s -- install
For systems that already have Nix installed, such as NixOS systems, read our install page
Building And Developing
See our Hacking guide in our manual for instruction on how to to set up a development environment and build Lix from source.
Additional Resources
License
Lix is released under the LGPL v2.1.