stack ghci can't load pthread unless running as Administrator

Question

When I run stack ghci on a brand-new project, it fails to load:

$ stack new repro simple
Downloading template "simple" to create project "repro" in repro\ ...

(Additional output omitted to make the question more readable.)

$ cd repro/

$ stack ghci
Using main module: 1. Package `repro' component repro:exe:repro with main-is file: C:\Users\mark\Desktop\repro\src\Main.hs
Building all executables for `repro' once. After a successful build of all of them, only specified executables will be rebuilt.
repro> configure (exe)
Configuring repro-0.1.0.0...
repro> initial-build-steps (exe)
Configuring GHCi with the following packages: repro
GHCi, version 8.6.5: http://www.haskell.org/ghc/  :? for help
<command line>: user specified .o/.so/.DLL could not be loaded (addDLL: pthread or dependencies not loaded. (Win32 error 5))
Whilst trying to load:  (dynamic) pthread
Additional directories searched:   C:\\Users\\mark\\AppData\\Local\\Programs\\stack\\x86_64-windows\\msys2-20180531\\mingw64\\lib
   C:\\Users\\mark\\AppData\\Local\\Programs\\stack\\x86_64-windows\\msys2-20180531\\mingw64\\bin
   C://Users//mark//AppData//Local//Programs//stack//x86_64-windows//ghc-8.6.5//mingw//bin/
   C://Users//mark//AppData//Local//Programs//stack//x86_64-windows//ghc-8.6.5//mingw//bin/../lib/
   C://Users//mark//AppData//Local//Programs//stack//x86_64-windows//ghc-8.6.5//mingw//bin/../lib/gcc/x86_64-w64-mingw32/7.2.0/
   C:/Users/mark/AppData/Local/Programs/stack/x86_64-windows/ghc-8.6.5/mingw/bin/../lib/gcc/x86_64-w64-mingw32/7.2.0/
   C:/Users/mark/AppData/Local/Programs/stack/x86_64-windows/ghc-8.6.5/mingw/bin/../lib/gcc/
   C:/Users/mark/AppData/Local/Programs/stack/x86_64-windows/ghc-8.6.5/mingw/bin/../lib/gcc/x86_64-w64-mingw32/7.2.0/../../../../x86_64-w64-mingw32/lib/../lib/
   C:/Users/mark/AppData/Local/Programs/stack/x86_64-windows/ghc-8.6.5/mingw/bin/../lib/gcc/x86_64-w64-mingw32/7.2.0/../../../../lib/
   C:/Users/mark/AppData/Local/Programs/stack/x86_64-windows/ghc-8.6.5/mingw/bin/../lib/gcc/x86_64-w64-mingw32/7.2.0/../../../../x86_64-w64-mingw32/lib/
   C:/Users/mark/AppData/Local/Programs/stack/x86_64-windows/ghc-8.6.5/mingw/bin/../lib/gcc/x86_64-w64-mingw32/7.2.0/../../../
   C:\Windows\system32

This is on Windows 10 (x64). I have another machine with a similar OS configuration and stack version, and on that machine, I have no problems. This seems to be an environment issue, but I can't figure out what it is.

I'm running from Git Bash, and if I run it as Administrator, it works:

$ stack ghci
Using main module: 1. Package `repro' component repro:exe:repro with main-is file: C:\Users\mark\Desktop\repro\src\Main.hs
Building all executables for `repro' once. After a successful build of all of them, only specified executables will be rebuilt.
repro> initial-build-steps (exe)
Configuring GHCi with the following packages: repro
GHCi, version 8.6.5: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( C:\Users\mark\Desktop\repro\src\Main.hs, interpreted )
Ok, one module loaded.
Loaded GHCi configuration from C:\\Users\\mark\\AppData\\Local\\Temp\\haskell-stack-ghci\\2524149e\\ghci-script
*Main>

I've been working with Stack for years on Windows, and this is the first time I've have to run as Administrator, and it really bothers me. What could be the issue, and how do I address it?

FWIW, this is the Stack version:

$ stack --version
Version 2.1.3, Git revision 0fa51b9925decd937e4a993ad90cb686f88fa282 (7739 commits) x86_64 hpack-0.31.2

This is the same version as I have on the other machine where the issue doesn't appear.

Examples here are copied from running Git Bash, but the issue is the same if I use cmd.

Jiggle

The error is "access denied", so could it be that the file in question somehow got restricted access control list, perhaps as a result of first downloading it as admin? Have you tried to nuke the stack cache? – Handedness

@FyodorSoikin Yes, I have tried to uninstall Stack, wiped C:\sr and %LOCALAPPDATA%\Programs\stack, as well as the local .stack-work directory, rebooted, installed Stack again; it makes no difference. – Jiggle

@FyodorSoikin Thanks to you, I was able to resolve the issue, as I've described in my answer. I do feel, however, that the solution is thanks to you, so if you wish to add an answer, I'll be happy to accept it. – Jiggle

No, that's fine. Amassing reputation is not my goal, and I didn't actually have an answer, just a hint of what to dig for. – Handedness

Answer 1

Thanks to Fyodor Soikin, I was able to track down the issue.

Summary

Give your user account Read & execute permissions to pthread.dll.

Details

I didn't understand why this new machine of mine exhibited this problem while another machine with the same OS and basically the same setup didn't have any problems.

On close inspection, it turned out that that other machine didn't have a pthread.dll file at all.

It did have quite a few copies of pthread.h, though, and I suppose that this was enough to enable Stack to build the code.

The new machine had pthread.dll in a few places, including a subdirectory of C:\Windows\System32\DriverStore, which implies to me that this file originally arrived via a driver that the new machine uses, but the old machine didn't have. It also has a copy of pthread.dll in C:\Windows\System32, but this file was extraordinarily locked down. My own user account didn't have Read or Execute rights to the file, but I could view and change the permissions in Administrator mode.

I gave the local Users group Read & execute rights to the file, after which everything seems to work as it's previously done on my other machines.

Jiggle

I can confirm that. On my machine, there are two copies of pthread.dll below C:\Windows: one is in System32 and one is in a subdirectory of System32\DriverStore. My standard user doesn’t have any permissions for the file in C:\Windows\System32. It seems to be shipped with a driver for an Intel broadband modem on my HP Elitebook. – Zora

Can confirm that giving read & execute rights solves the issue. – Kristofer

Just in case anyone was wondering how to do that, here are the steps for Windows 10: Right click on the dll > Properties > Select the "Security" tab > click "Advanced" button (should take you to the Permissions tab) > click "Change permissions" button (at this point it will ask you to elevate to Administrator) > click "Add" button > click "Select a principal" link > Enter "Users" (no quotes) in the text box > select what access permissions to grant (at least read and execute) > click OK > click OK > click OK. You should be able to see the new group with its access permissions – Niveous

Answer 2

Just in case anybody else runs into this problem and you cant change the permissions on phtread.dll - another work-a-round is to take a copy of pthread.dll and place it in one of the "Additional directories searched" - in my case I copied pthread.dll from C:\Windows\system32 => C:/tools/ghc-9.6.2/mingw/lib/clang/14.0.6

It put up a warning about requiring System Admin permissions to copy the file but went ahead without me entering in any additional username / password. The copy had the necessary permissions by default and I can now run "ghci" without error on my nailed down corporate laptop

Phonon