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I'm extending mono/tests with next:
// simple return some pointer (from some allocator)
LIBTEST_API void* STDCALL
// define returning struct
public struct custom_ptr
public IntPtr value;
and in Main method adding follow:
custom_ptr cp = mono_return_custom_ptr();
Running pinvoke11.exe with any of this Mono Runtimes on Ubuntu 11.10:
Mono 2.10.6 (built from sources)
Mono latest (built from sources)
got invalid result:
Note, that this technique works fine with Mono 2.10.6 on Windows.
Sorry, i got this behaviour on X86 platform.
Same test works fine with .NET 4.
Your p/invoke binding is incorrect: if the native code returns a pointer, the managed method signature must return a pointer as well. In a similar case, if the native code returned a structure containing a pointer, the managed signature would need to return a struct with a pointer.
The incorrect code happens to work on windows because the ABI there says that small structures get returned in a register (which happens to be the same register where a pointer would be returned), while on Linux they are returned with a different mechanism.
Thanks for clear explanation!