Exit code is wrong with dynamically loaded libraries

Here's a simple scenario that goes wrong:

Program starts, calls hs_init(), hs_init_count=1

Program loads some Haskell library that calls hs_init(), hs_init_count=2.

Program does exitWith 99, which calls shutdownHaskellAndExit(99), which calls hs_exit_(). Since hs_init_count>1 it will do nothing. Control returns to shutdownHaskellAndExit, since hs_init_count>0 it will do nothing, i.e., it throws away the exit code 99.

Now real_main() gets control back, and calls shutdownHaskellAndExit(0). The whole program now exits with code 0, rather than 99.

The solution is probably to track the last non-0 exit code encountered in shutdownHaskellAndExit and use that as the exit code in real_main().

Trac metadata

Trac field	Value
Version	7.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Runtime System
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed weight to 5

added RTS Tbug Trac import labels

Attached file ghcShutdown.patch (download).

proposed fix

I attached a proposed patch. (The line numbers might be slightly off, because my copy of the ghc sources is a couple of months old.)

Does this fix have any justification other than that it works in your scenario? I'm struggling to understand exactly who is at fault here.

Another alternative that might be more correct is for shutdownHaskellAndExit to set hs_init_count to 1 before calling hs_exit, so that it definitely shuts down the RTS. The justification is that we're about to exit!

It's clearly an RTS bug. All the application is doing is to loading a shared library which will call hs_init() (unless calling hs_init(0 more than once is now banned) and then trying to exit.

I don't know what you think the proper fix is. Right now we FFI import stg_exit() and call that instead of exitWith, and that works.

Ok, I'm not claiming it's not an RTS bug, just trying to figure out what assumption has been broken to find out where to apply a fix.

I think that shutdownHaskellAndExit() should do exactly what it says on the tin: shut down the RTS regardless of how many hs_inits there have been previously, and then exit. It sounds like that would work in your case - would it?

If shutdownHaskellAndExit() did just that it would work fine.

We'll probably do a binary patch to 6.12.3 to fix the urgent problem.

mentioned in commit d18b5d53

mentioned in commit 2d7de127

closed

changed milestone to %7.4.1

Fixed, test added.

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed
Test case	→ ffi/should_run/5402

reopened

changed milestone to %7.2.2

added 1 deleted label

closed

removed 1 deleted label

Merged as changeset:d23fcba5

mentioned in commit 9cbcdb48

added Pnormal label