It's true that one must initialize the runtime when calling Haskell from C/C++. We do this in the real project and just a pair of calls hs_init/hs_exit causes memory to be leaked even faster. But I tried to construct the minimal example to describe the bug, so I reduced all the extra-code.

пн, 27 авг. 2018 г. в 18:00, Vanessa McHale <vanessa.mchale@iohk.io>:

I don't know about C++, but I do know that when calling Haskell from C code one must initialize the runtime and then exit it once finished. I also know that one must only initialize the runtime once over the course of the program's run. As far as I can tell, this does not occur in your example.


On 08/27/2018 09:44 AM, Ольга Филиппская wrote:
Hello.

Summary: memory is consumed without releasing when a Haskell DLL (that uses FFI) is loaded and unloaded in an endless loop.

Details: I'm working on a C++ project relying on a DLL that uses Haskell code. The DLL was built with GHC 8.0.1 x64, OS is Windows 7. (Newer versions of GHC - 8.2.1 and later - do not allow you to build such DLLs due to some bugs: ticket #1, ticker #2). The C++ project was built with MSVC compiler 2015.

We noticed that memory is not released when the library is unloaded. I've constructed a baseline example to reproduce the bug. It has three files: the first one is HaskellSources.hs(see attachments). It contains one foreign export function foo. This foreign export function is necessary to reproduce the bug. The second file is CWrapper.cpp. I intentionally didn't include any Haskell function export because they make no difference for this example. The last file is the code of the main program (see main.cpp) that loads the library and unloads it at once in an endless loop.

There are two cases: whether HaskellExports.o is included into the library or not.
1. HaskellExports.o is not included into the library (see attached build script build_no_hs.sh). Everything works just fine (i.e. amount of memory consumed by the app is the same before DLL loading and right after unloading.)
2. HaskellExports.o is included into the library (see build_w_hs.sh). Memory is not released after unloading the DLL, after repeated load/unload cycles memory consumption keeps growing until finally the application crashes.

Is this a known problem? Is it tracked in your bugtracker? (Or maybe it is not a problem at all and I'm doing it wrong).

Thank you for your time.

--
Olga Philippskaya
.


_______________________________________________
ghc-devs mailing list
ghc-devs@haskell.org
http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
_______________________________________________
ghc-devs mailing list
ghc-devs@haskell.org
http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs


--
Филиппская Ольга.