Unable to use 'libjulia.dll' in a C# application on Windows 8.1

[sliekens]

The documentation gave me the impression that I can use .NET P/Invokes to run Julia scripts in a .NET environment. I tried porting the embedding.c program to C#, but I always get one or more errors.

My code:

using System.Runtime.InteropServices;

class Program
{
    [DllImport("libjulia.dll")]
    public static extern void jl_init(string julia_home_dir);

    [DllImport("libjulia.dll")]
    public static extern void jl_eval_string(string str);

    static void Main(string[] args)
    {
        jl_init(null);
        jl_eval_string("print(sqrt(2.0))");
    }
}

When executed, it throws an AccessViolationException, which I believe is the .NET equivalent of a segfault.

.\Program.exe

Please submit a bug report with steps to reproduce this fault, and any error messages that follow (in their entirety). Thanks.
Exception: EXCEPTION_ACCESS_VIOLATION at 0x5a6e35f324 -- unknown function (ip: 1849029412)
unknown function (ip: 1849029412)
abstract_call_gf at inference.jl:622
unknown function (ip: 1840590556)
abstract_call at inference.jl:835
unknown function (ip: 1840590556)
abstract_eval_call at inference.jl:927
abstract_eval at inference.jl:952
unknown function (ip: 1840590556)
abstract_interpret at inference.jl:1115
unknown function (ip: 1840590556)
typeinf at inference.jl:1436
at (unknown line)
unknown function (ip: 1840590556)
typeinf_ext at inference.jl:1236
unknown function (ip: 1840590556)
unknown function (ip: 1840586610)
unknown function (ip: 1840588250)
unknown function (ip: 1840590657)
unknown function (ip: 1840641231)
unknown function (ip: 1840890118)
unknown function (ip: 1840863696)
unknown function (ip: 1840926177)
unknown function (ip: -1234565522)
unknown function (ip: -1235658528)
unknown function (ip: -1104811560)
unknown function (ip: -1104811200)
unknown function (ip: -1104811384)
unknown function (ip: -1104812144)
unknown function (ip: 1)
unknown function (ip: -879819355)
unknown function (ip: 373044544)
unknown function (ip: -1104811200)
unknown function (ip: -1235658528)
unknown function (ip: -1235658528)
unknown function (ip: -1104812144)
unknown function (ip: -1234565522)
unknown function (ip: -1104812112)
unknown function (ip: -1235658528)
unknown function (ip: -879819355)
unknown function (ip: -1102667552)
unknown function (ip: 1840926111)

Please submit a bug report with steps to reproduce this fault, and any error messages that follow (in their entirety). Thanks.
Exception: EXCEPTION_ACCESS_VIOLATION at 0x5a6e35f324 -- unknown function (ip: 1849029412)
unknown function (ip: 1840926112)

Please submit a bug report with steps to reproduce this fault, and any error messages that follow (in their entirety). Thanks.
Exception: EXCEPTION_ACCESS_VIOLATION at 0x5a6e35f324 -- unknown function (ip: 1849029412)
unknown function (ip: 1840926112)

Please submit a bug report with steps to reproduce this fault, and any error messages that follow (in their entirety). Thanks.
Exception: EXCEPTION_ACCESS_VIOLATION at 0x5a6e35f324 -- unknown function (ip: 1849029412)
unknown function (ip: 1840926112)

Please submit a bug report with steps to reproduce this fault, and any error messages that follow (in their entirety). Thanks.
Exception: EXCEPTION_ACCESS_VIOLATION at 0x5a6e35f324 -- unknown function (ip: 1849029412)
unknown function (ip: 1840926112)

Please submit a bug report with steps to reproduce this fault, and any error messages that follow (in their entirety). Thanks.
Exception: EXCEPTION_ACCESS_VIOLATION at 0x5a6e35f324 -- unknown function (ip: 1849029412)
unknown function (ip: 1840926112)

Please submit a bug report with steps to reproduce this fault, and any error messages that follow (in their entirety). Thanks.
Exception: EXCEPTION_ACCESS_VIOLATION at 0x5a6e35f324 -- unknown function (ip: 1849029412)
unknown function (ip: 1840926112)

Unhandled Exception: System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
at Brain2.Julia.Console.Program.jl_init(String julia_home_dir)
at Brain2.Julia.Console.Program.Main(String[] args)

I'm using Visual Studio 2012 and .NET 4.5

Tested with v0.3.2 (Current Release) for both x86 and x64 and also with v0.4.0-dev-7a7110b-win64

Julia Version 0.4.0-dev+1318
Commit 7a7110b* (2014-10-27 03:52 UTC)
Platform Info:
System: Windows (x86_64-w64-mingw32)
CPU: Intel(R) Core(TM) i7-4700MQ CPU @ 2.40GHz
WORD_SIZE: 64
BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
LAPACK: libopenblas
LIBM: libopenlibm
LLVM: libLLVM-3.3

[ihnorton]

What OS? I've tested the same code under Windows 7 and it worked fine. However, another user reported such an access violation on Windows 8.1.

[sliekens]

Windows 8.1, not tested on any other platform.

[sliekens]

What's confusing is that the interactive shell has no such problems, even on windows 8. What is my program doing that the interactive shell is doing differently? It's just two lines of code.

[ihnorton]

p/invoke'ing unmanaged code is quite different from running the interactive shell. It is entirely possible that there is some weird DLL interaction - this wouldn't be the first time.

However, a very quick google suggested that people have seen these violations with p/invoke'd code due to corrupt .NET installations when the system has been upgraded from Win7->8. If that is the history of your computer, you could consider updating or reinstalling the .NET SDK.

I'm not sure if any of the active developers have access to Win8/8.1 (I don't) so we will likely have to rely on detailed debugging feedback from you (and patches are very much encouraged!). A first step would be to run the code under the Visual Studio debugger and see if you can step in to jl_init.

[sliekens]

I've dabbled in C before, but not nearly enough to even know how to attach a debugger to this thing and figure out why the code crashes.

By the way, Microsoft offers pre-built virtual machines and evaluation licenses of every major version of their operating system, including Windows 8. See: https://www.modern.ie/en-us/virtualization-tools#downloads

The offer is meant for web developers, but it doesn't seem like the license is restricted to web development.

[tkelman]

I have Windows 2012 R2 in a packer VM that I can try this on, but my knowledge of .NET is almost nonexistent. I think I can get VS 2012 express installed command-line via chocolatey. Is there a command-line way to compile the C# example? I'm not sure if the VS IDE will be usable enough under a VM.

[vtjnash]

also possible that the stack of your .NET application is too small. default is 1MB, recommended is 8MB (the linux default). you need at least a 3MB stack to build julia.

[sliekens]

I'm targeting the precompiled binaries in my [DllImport] code. Any chance that the way that those binaries were compiled has anything to do with this "weird DLL interaction"? Can I compile the source myself using Microsoft's VC++ compiler?

[tkelman]

@StevenLiekens do you mean the libjulia source code? Yes you can (or, should be able to... I hope) compile it from source with MSVC, see #7761, but it's pretty hacky, experimental, not first-class or documented yet, and many things in Julia are broken due to limitations of MSVC. If you want to help improve these matters that'd be awesome.

[sliekens]

Still poking around with this. The call to jl_init() executes without crashing if I explicitly specify a path for julia_home_dir. The call to jl_eval_string() still crashes with an AccessViolationException.

Almost forgot to mention that this behavior is for a .2.x release (just because). I'll go try a 0.3.x release now.

Update: the same jl_init() code does not work for anything newer than .2.

class Program
{
    [DllImport("libjulia.dll")]
    public static extern void jl_init(string julia_home_dir);

    [DllImport("libjulia.dll")]
    public static extern void jl_eval_string(string str);

    static void Main(string[] args)
    {
        // Pass
        jl_init(@"C:\Users\steven liekens.BRAIN2\AppData\Local\julia-e44b593905\bin");

        // Crash
        jl_eval_string("print(sqrt(2.0))");
    }
}

[JeffBezanson]

Have you tried telling .NET to use a larger stack (see @vtjnash comment above)? Unfortunately I don't know how to do this, so I can't help much further.

[vtjnash]

jl_eval_string may do some messy setjmp stuff on the stack. i'm hoping to remove that extra bit of complication with #9266. not sure if that could be directly the cause however, since the net result should be minor