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
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 https://ghc.haskell.org/trac/ghc/ticket/14472#no2, ticker #2 https://ghc.haskell.org/trac/ghc/ticket/14784#no1). 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 .*
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-- *Филиппская Ольга.*