nix-instantiate terminated by signal 11, --show-trace has no effect

[peti]

Define the following attribute in ~/.nixpkgs/config.nix

{
  packageOverrides = pkgs:
  {
    crashNix = pkgs.haskellPackages.ghcWithPackages (self: [pkgs.haskellPackages.hledgerWeb]);
  };
}

and run:

$ nix-build ~/.nix-defexpr -A crashNix --show-trace
nix-instantiate killed by signal 11

This may very well be a bug in the ghtWithPackages expression, but I'm having a hard time finding out what the problem might be (since that wrapper works just fine for almost any other attribute set). Any suggestions how to remedy this issue are highly welcome.

[edolstra]

A segfault in the evaluator is usually due to an infinite recursion in the Nix expression. GDB says:

#0  0x00007ffff7976505 in nix::ExprOpConcatLists::eval(nix::EvalState&, nix::Env&, nix::Value&) ()
   from /nix/store/9n6swhw1qr71f8xls4i4dzfbmnachgv3-nix-1.1pre2718_8da6772/lib/nix/libexpr.so.0
#1  0x00007ffff797e47d in nix::EvalState::forceValue(nix::Value&) () from /nix/store/9n6swhw1qr71f8xls4i4dzfbmnachgv3-nix-1.1pre2718_8da6772/lib/nix/libexpr.so.0
#2  0x00007ffff7976482 in nix::ExprVar::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/9n6swhw1qr71f8xls4i4dzfbmnachgv3-nix-1.1pre2718_8da6772/lib/nix/libexpr.so.0
#3  0x00007ffff7976523 in nix::ExprOpConcatLists::eval(nix::EvalState&, nix::Env&, nix::Value&) ()
   from /nix/store/9n6swhw1qr71f8xls4i4dzfbmnachgv3-nix-1.1pre2718_8da6772/lib/nix/libexpr.so.0
#4  0x00007ffff797e47d in nix::EvalState::forceValue(nix::Value&) () from /nix/store/9n6swhw1qr71f8xls4i4dzfbmnachgv3-nix-1.1pre2718_8da6772/lib/nix/libexpr.so.0
#5  0x00007ffff7976482 in nix::ExprVar::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/9n6swhw1qr71f8xls4i4dzfbmnachgv3-nix-1.1pre2718_8da6772/lib/nix/libexpr.so.0
#6  0x00007ffff7976523 in nix::ExprOpConcatLists::eval(nix::EvalState&, nix::Env&, nix::Value&) ()
   from /nix/store/9n6swhw1qr71f8xls4i4dzfbmnachgv3-nix-1.1pre2718_8da6772/lib/nix/libexpr.so.0
...

repeated a few thousand times.

[kosmikus]

I've tested a bit, and I think it's not a bug in ghcWithPackages, but rather an actual problem in Nix. I've tried to add dependencies of hledgerWeb to the list instead of hledgerWeb itself, and it turns out that if I add both yesod and yesodDefault to the list, I get a segfault, but if I choose only one of the two, I don't.

[kosmikus]

It seems I can "fix" this by changing the definition of the library function closePropagation which is used by ghcWithPackages, so that it produces smaller intermediate lists while running. However, I think that only qualifies as a workaround. Nix shouldn't just segfault if something gets too large.

[peti]

How do we proceed with this issue? Would it be possible to commit the fix to closePropagation as a quick work around?

[edolstra]

@kosmikus, can you commit your fix? In general Nix expressions shouldn't recurse too deeply because the C stack is not infinite (well, not until we can use GCC's -fsplit-stack). The crashNix expression goes over 80000 levels deep.

It would be nice to give a better error message than "signal 11", but there is no portable way to detect a stack overflow.

[kosmikus]

I had hesitated committing the fix because these are central library functions which may affect other things, and I haven't checked if my new version returns all results in the same order. But yes, I can try to do it.

[kosmikus]

Committed as NixOS/nixpkgs@3fbd694.

[peti]

The crashes in ghcWithPackages are now gone.