pthread link errors on linux with GHC 8.2

[simonmichael]

On Ubuntu 16.04.1 LTS, stack install pandoc-2.0.4 is failing to link pthread functions:

...
[116 of 116] Compiling Text.Pandoc.App  ( src/Text/Pandoc/App.hs, .stack-work/dist/i386-linux/Cabal-2.0.1.0/build/Text/Pandoc/App.o )                                                                                                                      
    Preprocessing executable 'pandoc' for pandoc-2.0.4..                                                                                                                                                                                                       
    Building executable 'pandoc' for pandoc-2.0.4..                                                                                                                                                                                                            
    [1 of 2] Compiling Main             ( pandoc.hs, .stack-work/dist/i386-linux/Cabal-2.0.1.0/build/pandoc/pandoc-tmp/Main.o )                                                                                                                                
    [2 of 2] Compiling Paths_pandoc     ( .stack-work/dist/i386-linux/Cabal-2.0.1.0/build/pandoc/autogen/Paths_pandoc.hs, .stack-work/dist/i386-linux/Cabal-2.0.1.0/build/pandoc/pandoc-tmp/Paths_pandoc.o )                                                   
    Linking .stack-work/dist/i386-linux/Cabal-2.0.1.0/build/pandoc/pandoc ...                                                                                                                                                                                  
                                                                                                                                                                                                                                                               
    /tmp/stack14939/pandoc-2.0.4/rts/posix/OSThreads.c:137:0: error:                                                                                                                                                                                           
         error: undefined reference to 'pthread_create'                                                                                                                                                                                                        
                                                                                                                                                                                                                                                               
    /tmp/stack14939/pandoc-2.0.4/rts/posix/OSThreads.c:139:0: error:                                                                                                                                                                                           
         error: undefined reference to 'pthread_detach'                   
...

Is there an ubuntu package I'm missing ? I didn't see this error when building 1.x.

[jgm]

This is with normal 'stack install'? Any special options? What ghc and stack versions?

[mb21]

If this is this ghc bug it should be fixed in GHC 8.1

[simonmichael]

This is a normal stack install, stack 1.6.1, nightly-2017-12-05 resolver, ghc 8.2.2.

[jgm]

This is odd, because we regularly do builds with cabal and ghc 8.2.2 on travis-ci, which uses Ubuntu. I noticed that we have a stack build with ghc 8.2.2 and nightly on ci, and it fails for the reasons you report: https://travis-ci.org/jgm/pandoc/jobs/312704463 I never looked into why, but we should figure this out. Cabal seems to work fine... +++ Simon Michael [Dec 07 17 22:44 ]:

…

This is a normal stack install, stack 1.6.1, nightly-2017-12-05 resolver, ghc 8.2.2. — You are receiving this because you commented. Reply to this email directly, [1]view it on GitHub, or [2]mute the thread. References 1. #4130 (comment) 2. https://github.com/notifications/unsubscribe-auth/AAAL5KbTEmUnQlTmR3b6ncj8iqnMN43sks5s-GpSgaJpZM4Q6ONB

[simonmichael]

More testing on this system:

stack install --resolver lts-9.17 in the pandoc source tree at 2.0.4 tag links successfully. (GHC 8.0.2)

cabal install pandoc-2.0.4 links successfully. This used the system GHC. (GHC 7.10.3)

cabal install pandoc-2.0.4 -w /home/simon/.stack/programs/i386-linux/ghc-8.2.2/bin/ghc fails with the same error. (GHC 8.2.2)

$ cabal install pandoc-2.0.4 -j -w /home/simon/.stack/programs/i386-linux/ghc-8.2.2/bin/ghc
...
Linking dist/build/pandoc/pandoc ...                                                                                                                                                 
                                                                                                                                                                                     
rts/posix/OSThreads.c:137:0: error:                                                                                                                                                  
     error: undefined reference to 'pthread_create'                                                                                                                                  
                                                                                                                                                                                     
rts/posix/OSThreads.c:139:0: error:                                                                                                                                                  
     error: undefined reference to 'pthread_detach'                                                                                                                                  
                                                                                                                                                                                     
rts/posix/OSThreads.c:141:0: error:                                                                                                                                                  
     error: undefined reference to 'pthread_setname_np'                                                                                                                              
                                                                                                                                                                                     
rts/posix/OSThreads.c:184:0: error:                                                                                                                                                  
     error: undefined reference to 'pthread_key_create'                                                                                                                              
                                                                                                                                                                                     
rts/posix/OSThreads.c:192:0: error:                                                                                                                                                  
     error: undefined reference to 'pthread_getspecific'                                                                                                                             
                                                                                                                                                                                     
rts/posix/OSThreads.c:203:0: error:                                                                                                                                                  
     error: undefined reference to 'pthread_setspecific'                                                                                                                             
                                                                                                                                                                                     
rts/posix/OSThreads.c:212:0: error:                                                                                                                                                  
     error: undefined reference to 'pthread_key_delete'                                                                                                                              
                                                                                                                                                                                     
rts/posix/OSThreads.c:371:0: error:                                                                                                                                                  
     error: undefined reference to 'pthread_kill'                                                                                                                                    
                                                                                                                                                                                     
includes/rts/OSThreads.h:59:0: error:                                                                                                                                                
     error: undefined reference to 'pthread_mutex_trylock'                                                                                                                           
collect2: error: ld returned 1 exit status                                                                                                                                           
`gcc' failed in phase `Linker'. (Exit code: 1)                                                                                                                                       
cabal: Leaving directory '/tmp/cabal-tmp-14784/pandoc-2.0.4'                                                                                                                         
cabal: Error: some packages failed to install:                                                                                                                                       
pandoc-2.0.4-3Gl6Xt4LcAi3gpzxmZMtTy failed during the building phase. The                                                                                                            
exception was:                                                                                                                                                                       
ExitFailure 1                                                                       

Following @mb21's lead: binutils on this system provides both ld and ld.gold. GHC 8.2.1 release notes say "GHC will now use ld.gold or ld.lld instead of the system’s default ld, if available. Linker availability will be evaluated at configure time. The user can manually override which linker to use by passing the LD variable to configure. You can revert to the old behavior of using the system’s default ld by passing the --disable-ld-override flag to configure."

I tried replacing /usr/bin/{gold,ld.gold} with symlinks to ld. This might not be a valid test. The format of the link error changed, but otherwise it seemed similar:

Linking .stack-work/dist/i386-linux/Cabal-2.0.1.0/build/pandoc/pandoc ...                                                                                                                                                                                                              
/usr/bin/ld.gold: /home/simon/.stack/programs/i386-linux/ghc-8.2.2/lib/ghc-8.2.2/rts/libHSrts.a(OSThreads.o): undefined reference to symbol 'pthread_create@@GLIBC_2.1'                                                                                                                
//lib/i386-linux-gnu/libpthread.so.0: error adding symbols: DSO missing from command line                                                                                                                                                                                              
collect2: error: ld returned 1 exit status                                                                                                                                                                                                                                             
`gcc' failed in phase `Linker'. (Exit code: 1)                                                                                                                                                                                                                                         

[jgm]

I tried adding -threaded to the executable stanza of cabal. Unfortunately, the travis build fails for stack + ghc 8.2.2 (looks like an out-of-memory issue compiling a dependent library). But why don't you try with the latest pull from master.

[simonmichael]

@jgm: that fixed it with GHC 8.2.2 here.

[jgm]

Excellent, I'll close this then.

[simonmichael]

Thanks for the support!

The cabal+ghc8.2 CI test probably should have failed like stack, it might need a tweak specifying GHC version.

[jgm]

+++ Simon Michael [Dec 08 17 21:16 ]:

Thanks for the support! The cabal+ghc8.2 CI test probably should have failed like stack, it might need a tweak specifying GHC version.

You can see from the log that it's using ghc 8.2.2. So I don't know why this worked for me and failed for you...

[hanjoosten]

@jgm what exactly did you do to fix this? I am still struggling with the build of Ampersand, using pandoc 2.0.6 with ghc 8.2.2. It builds fine with cabal, but the stack build fails, even as I enabled -threaded flag.

[jgm]

@hansjoosten it looks like it's pandoc-crossref that is failing in your build. Perhaps it needs the threaded flag in its cabal file? If this works, you might alert the author.

[hanjoosten]

Thanks. I guess you are right. The -threaded option was only in the executable, not with the library. I asked @lierdakil to kindly add it.

[lierdakil]

Warning: 'ghc-options: -threaded' has no effect for libraries. It should only
be used for executables.

Did that change with GHC 8.2?

[jgm]

+++ Nikolay Yakimov [Jan 15 18 22:01 ]:

Warning: 'ghc-options: -threaded' has no effect for libraries. It should only be used for executables. Did that change with GHC 8.2?

I'm not aware of any such change. In pandoc we only use -threaded on the executable.