[libvirt] [PATCH] Change/create solution and project for Visual Studio and MonoDevelop for C# bindings

[arnaud.champion at devatom.fr]

The problem with DllMap, is that it works only under Mono, not under .Net 
:(

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From: "Matthias Bolte" <matthias.bolte at googlemail.com>
Sent: Tuesday, October 19, 2010 6:38 PM
To: <arnaud.champion at devatom.fr>
Cc: <libvir-list at redhat.com>
Subject: Re: [libvirt] [PATCH] Change/create solution and project for Visual 
Studio and MonoDevelop for C# bindings

> 2010/10/19  <arnaud.champion at devatom.fr>:
>> Hi,
>>
>> here are 2 patches for C# libvirt bindings.
>>
>> These patches create a new solution/project couple for Visual Studio 2010
>> with also a sample code and a solution/project couple for MonoDevelop 
>> with a
>> sample code also.
>>
>> The sample code have been tested under .Net/Windows, Mono/Windows and
>> Mono/Linux. And it works, the sample code consist of the using au
>> virConnectOpenAuth and callback handling. It connect to a URI (I have 
>> made
>> my tests with ESX hypervisor only) and list domains in a listbox.
>>
>> So, to summarize, code work under linux or windows, the binary library 
>> name
>> depends of a project directive (a kind of pragma). When the directive
>> WINDOWS is declared, DllImport will try to find "libvirt-0.dll" (for
>> windows) otherwise it looks for "libvirt.so.0" (for linux). For now, in 
>> the
>> same manner, when the directive WINDOWS is declared, we find _strdup in
>> "msvcrt.dll" otherwise we look in "libc.so.6".
>
> This makes the resulting binary platform dependent. I asked a friend
> about this and he suggested to use Mono's dllmap feature [1]. It
> allows you to stick with [DllImport("libvirt-0.dll")] in the code for
> .Net and have Mono use libvirt.so.0 on Linux and libvirt.dylib on OSX.
> This result in a platform independent binary regarding this issue.
>
> [1] http://www.mono-project.com/Config_DllMap
>
>> I'm currently trying to remove strdup call by Custom Marshaling but it 
>> seems
>> that .Net (or Mono anyway) doesn't allow to use custom marshaler with
>> structure (and we need it for virConnectCredential structure). If anyone 
>> had
>> an idea...
>
> Regarding this issue my friend suggested to stop libvirt from taking
> ownership of cred.result. We could do that by making
> virConnectOpenAuth take a new VIR_CONNECT_COPY_CRED_RESULT (or
> VIR_CONNECT_DONT_FREE_CRED_RESULT or VIR_CONNECT_CONST_CRED_RESULT)
> flag that lets libvirt internally strdup() cred.result before passing
> it to the driver. That way the C# bindings could pass a managed string
> as cred.result and we don't need to Marshal.StringToHGlobalAuto() and
> strdup in C# at all.
>
> Or we could make libvirt take a custom free function to free
> cred.result instead of free(). That way Marshal.FreeHGlobal could be
> used or no free function at all and you pass a managed string to it.
> This would probably require a new version of virConnectOpenAuth and I
> consider this as too invasive.
>
> Another possibility would be to add a public virAlloc to libvirt that
> C# can use to allocate memory that can be freed using free().
>
> Matthias