Re: [Haskell-cafe] Need help with very simple C++ FFI call

On Tue, Nov 19, 2013 at 11:31 AM, Thiago Padilha wrote:

On Tue, Nov 19, 2013 at 1:19 PM, Brandon Allbery wrote:

...

Also note that different memory allocators have different behaviors;

Line 14(which causes the segfault) comment says the HandleScope is being allocated on the stack:

// Create a stack-allocated handle scope. HandleScope handle_scope(isolate);

I dont know any C++. Is it possible that this line of code is allocating something on the heap? If so could ghci have overriden memory allocation routines in a way that would mess that allocation?

I don't think ghc/ghci overrides malloc() like that. And it is possible that the constructor, while allocating a stack object, also allocates some heap-based memory; but that is a detail of the C++ code of the constructor. That said, I believe g++ uses malloc/free behind the scenes for new/delete to avoid such conflicts (this is common because it is often necessary to mix C and C++ code, and it's just bad to have multiple memory allocators working in the same heap). (That said, the fact that it uses malloc/free behind the scenes does *not* guarantee that you can substitute malloc() for new/new[] or free() for delete/delete[]. But in this case, no C++ allocations should be escaping the C++ code, so that also should not be relevant.) It might be a good idea to run the test program under valgrind and see what it has to say about the problem. -- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net