Hi Jeff, thanks for the quick reply. If "Any" is used as the return type of the ccall, the result will be > treated as a julia reference and you can skip > unsafe_pointer_to_objref. >
If returning "Any", would the GC take care of it? > > A variant of this is to allocate the array in julia, and pass it to > the C function to be filled in (ccall will effectively call > jl_array_ptr for you to pass the array to C). > Right, but if the final size is not known before ccall(), then it may not be as easy as creating it from C. Now, I am also looking for something a bit more involved. For example, I need to return what in C is an array of structs (std::vector<struct type>). Do you see some problems when creating and filling a specific Julia type, to add several of them into a Julia array? Would you point me to some of the functions of the API that could be used for this? Thanks, Carlos > > On Sat, Feb 8, 2014 at 2:21 PM, Carlos Becker > <carlos...@gmail.com<javascript:>> > wrote: > > Hello everyone, > > > > I just got started with Julia, and I wanted to try to wrap a C/C++ > library > > to Julia to check whether it would work out for my purposes. > > > > I tried out many ways of passing arrays and other objects from C back to > > Julia. > > So far it seems that it takes a lot of extra code if I want to return, > for > > example, a simple double-array or an array of types (eg structs). > > > > Then I thought that I could call the Julia API from the ccalled binary, > to > > allocate an array and return it to julia, > > then use unsafe_pointer_to_objref() and get a neat Julia object > directly. > > > > You can see a very simple example here > > https://gist.github.com/anonymous/8888647 > > > > This would simplify _significantly_ a lot of code from the C side, at > least > > with what I am working right now. > > > > Now, my question is: is it safe to call functions such as > > jl_alloc_array_1d() from the C binary? > > would this be a problem in some situations? > > > > I understand that it may mess memory up if those functions are called > > outside the main thread, but I would certainly not do that. > > > > Thanks in advance, > > Carlos >
