[Haskell-cafe] Using GHC option '-optl-static' causes segfault

[Victor Adossi]

While I also like static binaries, most people do not necessarily need
or want them -- changing the default for GHC to be built with musl would
be a huge risk, IMO. More concretely, while GHC has a maintained alpine
linux package (which is based on musl), stack does not -- see
https://github.com/commercialhaskell/stack/issues/2387.

I've written about it a little bit
(https://vadosware.io/post/static-binaries-for-haskell-a-convoluted-approach/),
the post is quite old so things have likely shifted.

Static linking for programs in linux is surprisingly hard (but possible
with some caveats), even when you get a library linked with musl (or
some other small libc) you often need to ensure that libnss is available
if you're going to do dns resolutions. One alternative that looks viable
is nsss (https://skarnet.org/software/nsss), but I've never actually
used it -- other languages like rust and go get around this by offering
domain name resolution at the language level
(https://doc.rust-lang.org/std/net/trait.ToSocketAddrs.html,
https://golang.org/pkg/net/#hdr-Name_Resolution). I'm not entirely sure
how easy this would be to do with haskell -- is the move to make a
haskell binding to nsss then using that? How easy is it to write a
haskell library that will include the relevant headers that make nsss
go? Here's the quick rundown on how one uses nsss:

> Application programs can use the internal API directly, or the
prefixed nsss_ functions directly. Most programs, however, will simply
use the standard pwd.h
<http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/pwd.h.html>,
grp.h
<http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/grp.h.html> or
shadow.h <http://man7.org/linux/man-pages/man3/getspnam.3.html>
interfaces. nsss provides a version of these standard headers: if an
application is built with these headers, then getpwnam() will
automatically be aliased to nsss_all_getpwnam(), and the other functions
will be aliased similarly.

Also, a cabal-based workflow might be better for building static haskell
binaries -- it's normally included with containers that have the
toolchain set up already like https://github.com/utdemir/ghc-musl (but
as I mentioned earlier, stack is not).

I *think* you could somewhat easily get stack to build a musl derived
binary by using the stack docker integration
(https://docs.haskellstack.org/en/stable/docker_integration/) -- again,
I haven't tried this but it'd be a good subject of a blog post at some
point.

Victor

On 3/10/20 2:10 PM, Nutr1t07 wrote:
> It's pretty weird that program compiled with '-optl-static' runs just
> well on my server Ubuntu 18.04.2 LTS (GNU/Linux 4.15.0-48-generic
> x86_64), but failed running on my PC Archlinux (x86_64 Linux
> 5.5.8-arch1-1).
>
> Since there are static compiling problems with glibc, why is the GHC
> in stack is still built with ghlic instead of musl?
>
> On 3/10/20 11:24 AM, Vanessa McHale wrote:
>> I’ve run into that before; I think it arises because you can’t link
>> statically against libc? In any case, trying to use network code
>> fails with a segfault.
>>
>> I think it is hard to work around; you need to build GHC against musl
>> and then use that to compile your program.
>>
>> Cheers,
>> Vanessa
>>
>>> On Mar 9, 2020, at 9:32 PM, Nutr1t07 <nutr1t07 at outlook.com> wrote:
>>>
>>> Hi,
>>>
>>> I added '-optl-static' in GHC option to make my program compiled
>>> statically. When I compiled the following code using 'stack build':
>>>
>>> -- Main.hs
>>>
>>> {-# LANGUAGE OverloadedStrings #-}
>>> module Main where
>>>
>>> import Web.Scotty                     as Scotty
>>> import Network.Wreq                as Wreq
>>> import Control.Monad.IO.Class
>>>
>>> main :: IO ()
>>> main = scotty 8443 $ do
>>>    Scotty.get (literal "/") $ do
>>>      _ <- liftIO $ Wreq.get "https://www.google.com/"
>>>      html "Could not see this"
>>>
>>> -- 
>>>
>>> Ran the compiled program and accessing "http://localhost:8443" would
>>> raise a segmentation fault.
>>>
>>> Here are what in my 'ghc-option':
>>>
>>>      ghc-options:
>>>      - -optl-static
>>>      - -threaded
>>>      - -rtsopts
>>>      - -with-rtsopts=-N
>>>
>>> Then I removed the '-optl-static', compiled it, and the program ran
>>> well.
>>>
>>> It seems that it something has to do with glibc. What can I do with
>>> this problem?
>>>
>>> Regards
>>>
>>> PS. I'm using GHC 8.8.2, stack 2.1.3
>>>
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