Returning a string to another process

Hello,

I have a program package for making HMI (Human-Machine Interface) systems (for industrial use), which includes a fairly primitive (it actually supports semaphores, internal multithreading among other things, not pointers and data structures, though) built in programming language. I want to expand its functionallity by writing a DLL (yes, I am able to make DLL calls from it) that opens a Windows window (WinAPI) and lets the user do various things. When the user is done, I want to return data from the DLL to my HMI system. When returning a single integer, this shouldn't be a problem, but, sometimes I want to return a string of characters or even several integers. Is this possible to do? I'm not too experienced with such programming, and I'm only at a learning stage, so any suggestions, examples, explanations of why or why not this will work are greatly appreciated! :-)

Thanks,
Eirik

I would think you should be able to do this. Instead of passing back a rc=0, pass back the pointer to your malloc()'ed storage where you put your message. Have the HMI free() it when finished with it.

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Originally Posted by Dino

I would think you should be able to do this. Instead of passing back a rc=0, pass back the pointer to your malloc()'ed storage where you put your message. Have the HMI free() it when finished with it.

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That is, if it's actually C...
But since a DLL is always loaded into the client process memory, they share they same virtual memory, so anything that is created inside the DLL - via dynamic allocation or something else - will also exist in the client, so passing pointers and references will be fine.

I didn't read the question or any of the answers....

GlobalAlloc() is the correct way to do this.

>> I didn't read the question or any of the answers....
Then how could you possibly contribute to anything other than your post count? :confused:

>> GlobalAlloc() is the correct way to do this.
If you're implying that the memory returned from GlobalAlloc is sharable across process boundaries, then that's just incorrect.
If you're referring to not using malloc() in one module, and free() in another (because that's bad) then that's correct - and using GlobalAlloc() is one away around that. Another option is to have a FreeData() interface in your DLL so that the same module that did the allocation can also do the de-allocation.
http://blogs.msdn.com/oldnewthing/ar...15/755966.aspx

gg

Thank you guys for all the answers, I'll do some fiddelin' and see what I can work out :-)