# How to dynamically embed Julia in a Windows app

**URL:** <https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133>\
**Category:** General Usage\
**Tags:** question, embedding\
**Created:** [December 4, 2023, 10:35pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133 "2023-12-04T22:35:12Z")\
**Posts on this page:** 16\
**Page:** 1

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**Author:** ![droodman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/droodman/32/26652_2.png) [@droodman](https://discourse.julialang.org/u/droodman)\
**Post date:** [December 4, 2023, 10:35pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/1 "2023-12-04T22:35:12Z")

</div>

I have written a plugin for the commercial statistical software Stata that bridges to Julia in order to exploit its speed. In an [issue thread on juliaup](https://github.com/JuliaLang/juliaup/issues/758), @davidanthoff and @staticfloat have helped me figure out how best to do this. But I’m still getting crashes on some Windows systems and am stuck.

Here is a MWE. It loads libjulia.dll, gets the address for the jl\_init() function, and then tries to call it. I compile this in Visual Studio while adding no extra libraries to link to but adding the Julia include folder so it finds juliah.h. It crashes on the last step.

```julia
#include <julia.h>
#include <iostream>
#include "windows.h"

typedef void (* myfn_t)(void);

int main() {
    HINSTANCE hDLL = LoadLibraryA("C:\\Users\\maihp\\.julia\\juliaup\\julia-1.9.4+0.x64.w64.mingw32\\bin\\libjulia.dll");
    myfn_t JL_init = (void (*)(void))GetProcAddress(hDLL, "jl_init");
    std::cout << "Didn't crash 1!\n";
    (JL_init)();
    std::cout << "Didn't crash 2!\n";
    return 0;
}

```

When I run the result, test.exe, in CMD, I get:

```julia
Microsoft Windows [Version 10.0.19045.2965]
(c) Microsoft Corporation. All rights reserved.

... [snip]

C:\Users\maihp\source\repos\julia.ado\x64\Release>test.exe
Didn't crash 1!
fatal: error thrown and no exception handler available.
InitError(mod=:Sys, error=ErrorException("could not load library "libpcre2-8"
The specified module could not be found. "))
ijl_errorf at C:/workdir/src\rtutils.c:77
ijl_load_dynamic_library at C:/workdir/src\dlload.c:369
jl_get_library_ at C:/workdir/src\runtime_ccall.cpp:48
jl_get_library_ at C:/workdir/src\runtime_ccall.cpp:39 [inlined]
ijl_load_and_lookup at C:/workdir/src\runtime_ccall.cpp:61
jlplt_pcre2_compile_8_33629.clone_1 at C:\Users\maihp\.julia\juliaup\julia-1.9.4+0.x64.w64.mingw32\lib\julia\sys.dll (unknown line)
compile at .\pcre.jl:161
compile at .\regex.jl:75
match at .\regex.jl:376
match at .\regex.jl:376 [inlined]
match at .\regex.jl:395 [inlined]
splitdrive at .\path.jl:38
joinpath at .\path.jl:264
joinpath at .\path.jl:327 [inlined]
abspath at .\path.jl:449 [inlined]
__init_build at .\sysinfo.jl:128
__init__ at .\sysinfo.jl:120
jfptr ___init___ 42494.clone_1 at C:\Users\maihp\.julia\juliaup\julia-1.9.4+0.x64.w64.mingw32\lib\julia\sys.dll (unknown line)
jl_apply at C:/workdir/src\julia.h:1880 [inlined]
jl_module_run_initializer at C:/workdir/src\toplevel.c:75
_finish_julia_init at C:/workdir/src\init.c:855
ijl_init_with_image at C:/workdir/src\jlapi.c:66 [inlined]
ijl_init_with_image at C:/workdir/src\jlapi.c:55 [inlined]
ijl_init at C:/workdir/src\jlapi.c:82
unknown function (ip: 00007ff70da2103a)
unknown function (ip: 00007ff70da214bf)
BaseThreadInitThunk at C:\WINDOWS\System32\KERNEL32.DLL (unknown line)
RtlUserThreadStart at C:\WINDOWS\SYSTEM32\ntdll.dll (unknown line)

```

To be clear, I have compiled on the same computer on which I’m getting the crash.

This is happening in Windows 10 Pro 22H2. At least one user reports the same thing in “Windows 11 Pro 64-bit”. It does not happen to me on another laptop with Windows 11 Pro 22H2. All systems have Julia 1.9.4.

Thanks for any help!

P.S. The motive for run-time rather than load-time linking to the Julia libraries is that in a juliaup world, there can be multiple versions on a machine, _none_ of whose shared libraries are visible to the linker at load time.

---

<div class="post-metadata">

**Author:** ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Post date:** [December 5, 2023, 4:31pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/2 "2023-12-05T16:31:26Z")

</div>

The first question to answer is whether Windows actually cannot find “libpcre2-8.dll” or if there anorher problem, perhaps with dependencies.

You will then want to use `gflags` and a Windows debugger as described here:

> **[Debugging DLL Loading Errors](https://ten0s.github.io/blog/2022/07/01/debugging-dll-loading-errors)**
>
> How to debug MSYS2/MinGW64/Cygwin/GTK/etc DLL loading errors

---

<div class="post-metadata">

**Author:** ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Post date:** [December 5, 2023, 4:41pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/3 "2023-12-05T16:41:24Z")

</div>

Essentially we will want the Debugging Tools for Windows:

> **[Debugging Tools for Windows - Windows drivers](https://learn.microsoft.com/en-us/windows-hardware/drivers/debugger/debugger-download-tools)**
>
> This page provides downloads for the Windows Debugging tools, such as WinDbg.

Then we will need `gflags`, the global flags editor.

> **[GFlags - Windows drivers](https://learn.microsoft.com/en-us/windows-hardware/drivers/debugger/gflags)**
>
> Learn how GFlags (the Global Flags Editor), gflags.exe, enables and disables advanced debugging, diagnostic, and troubleshooting features.

Run `gflags` by itself to get a dialog box with options.

Next you want to enable loader snaps to trace the Windows DLL loader.

So we do `gflags /i stata.exe +sls` or whatever the entry point is.

Next you have to run the program under a debugger.

---

<div class="post-metadata">

**Author:** ![droodman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/droodman/32/26652_2.png) [@droodman](https://discourse.julialang.org/u/droodman)\
**Post date:** [December 5, 2023, 5:25pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/4 "2023-12-05T17:25:54Z")

</div>

Thanks @mkitti. Yes, libpcre2-8.dll is in my Julia bin folder, next to julia.exe and all the other dll’s. I should have mentioned that.

I’ve already run it in the Visual Studio debugger. The error in Visual Studio is

```julia
Exception thrown at 0x0000000000000000 in Project1.exe: 0xC0000005: Access violation executing location 0x0000000000000000. 

```

My guess is that the error is much easier to understand than fix. I think it is occurring because Windows doesn’t know to look for DLL’s in the Julia bin directory. Because when using juliaup, no Julia bin directory (and there will be more than 1 if you have multiple installation channels) is in PATH. Only the directory holding the juliaup executable, or a shortcut to it, is in PATH. My little program is able to load libjulia.dll because I provide it the exact path. But if that DLL contains code that wants to call a function in another Julia DLL, like libjulia-internal.dll or libpcre2-8.dll, then it’s stuck.

I tried inserting

```julia
HINSTANCE hDLLlibpcre28 = LoadLibraryA("C:\\Users\\maihp\\.julia\\juliaup\\julia-1.9.4+0.x64.w64.mingw32\\bin\\libpcre2-8.dll");

```

to load the missing library that way, but it didn’t change the error.

So for me this leads to the question in the title of the post: how does one embed Julia in a Windows app for distribution? Is there some way to tell Windows, when loading a DLL at run time, where to look for other DLLs that the explicitly loaded one is referencing?

Or to turn that around, do I need to tell my Windows users not to use juliaup? According to my limited understanding, in Linux and macOS, there is just one shared library file, libjulia.so, so this issue does not arise. (I think…)

If I could somehow guarantee that all the Julia dll’s are copied into the same folder as Stata.exe–the application for which I’ve written the plugin–that might work. But that is not really practical.

---

<div class="post-metadata">

**Author:** ![davidanthoff](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/davidanthoff/32/223493_2.png) [@davidanthoff](https://discourse.julialang.org/u/davidanthoff)\
**Post date:** [December 5, 2023, 5:39pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/5 "2023-12-05T17:39:47Z")

</div>

Could the problem also be related to different C runtime libraries? I believe Julia uses msvcrt.dll (which is the very old version of it that ships as part of Windows for backwards compat reasons that MS would really like everyone to _not_ use), but Visual Studio presumably would use more modern versions of the runtime C library. @staticfloat would probably know more 🙂

I don’t think this is related to `PATH`, Julia itself also works if the dlls are not on the `PATH`.

---

<div class="post-metadata">

**Author:** ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Post date:** [December 5, 2023, 6:27pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/6 "2023-12-05T18:27:49Z")

</div>

I’m unclear if you used `gflags` or not and what the error has to fo with the stacktrace. Did you try to continue execution past the “access violation”?

Here is how the DLL search order works on Windows:

> **[Dynamic-link library search order - Win32 apps](https://learn.microsoft.com/en-us/windows/win32/dlls/dynamic-link-library-search-order)**
>
> You can control the specific location from which any given DLL is loaded by specifying a full path. If you don't use that method, then the system searches for the DLL at load time as described in this topic.

---

<div class="post-metadata">

**Author:** ![droodman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/droodman/32/26652_2.png) [@droodman](https://discourse.julialang.org/u/droodman)\
**Post date:** [December 5, 2023, 6:30pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/7 "2023-12-05T18:30:40Z")

</div>

> [@mkitti](#):
>
> Here is how the DLL search order works on Windows:

Right. I believe that when Julia is installed with juliaup, the Julia dll’s appear nowhere in the list of places that Windows checks.

---

<div class="post-metadata">

**Author:** ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Post date:** [December 5, 2023, 6:32pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/8 "2023-12-05T18:32:48Z")

</div>

Set the gflags like I suggested above and then the debugger will tell you exactly where Windows is looking for libraries or why it cannot load anything.

---

<div class="post-metadata">

**Author:** ![Janis\_Erdmanis](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/janis_erdmanis/32/10869_2.png) [@Janis\_Erdmanis](https://discourse.julialang.org/u/Janis_Erdmanis)\
**Post date:** [December 5, 2023, 6:58pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/9 "2023-12-05T18:58:39Z")

</div>

This error is also raised when one tries to bundle Julia in a MSIX bundle for which I oppened [#52007](https://github.com/JuliaLang/julia/issues/52007) issue. From what I skimmed through the solution seems to be recompiling julia and all it’s libraries with `/ZW` flag.

---

<div class="post-metadata">

**Author:** ![droodman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/droodman/32/26652_2.png) [@droodman](https://discourse.julialang.org/u/droodman)\
**Post date:** [December 5, 2023, 7:37pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/10 "2023-12-05T19:37:18Z")

</div>

I think I solved it for my case!

This substitutes for the `LoadLibraryA()` call in my example:

```julia
    SetCurrentDirectoryA(libdir);
    hDLL = LoadLibraryExA(fulllibpath, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);

```

where `libdir` is the path to the /bin folder and `fulllibpath` is that + “libjulia.dll”.

I think it is also possible to do it with `AddDllDirectory()` and then `LoadLibraryExA(fulllibpath, NULL, LOAD_LIBRARY_SEARCH_USER_DIRS)` but `AddDllDirectory()` requires a wide/Unicode string and I’d rather avoid the complication.

---

<div class="post-metadata">

**Author:** ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Post date:** [December 5, 2023, 8:20pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/11 "2023-12-05T20:20:17Z")

</div>

You may be interested in [Use modern, secure, Windows API for dlopen](https://discourse.julialang.org/t/use-modern-secure-windows-api-for-dlopen/90171)

---

<div class="post-metadata">

**Author:** ![GunnarFarneback](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gunnarfarneback/32/1827_2.png) [@GunnarFarneback](https://discourse.julialang.org/u/GunnarFarneback)\
**Post date:** [December 5, 2023, 8:32pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/12 "2023-12-05T20:32:52Z")

</div>

Not exactly answering your question but given what you’re doing you may find [GitHub - GunnarFarneback/DynamicallyLoadedEmbedding.jl: Embed Julia with dynamical loading of libjulia at runtime.](https://github.com/GunnarFarneback/DynamicallyLoadedEmbedding.jl) interesting, if you’re not already familiar with it.

(I should add some documentation about juliaup there, since I’ve recently updated the application which the package is based on.)

---

<div class="post-metadata">

**Author:** ![droodman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/droodman/32/26652_2.png) [@droodman](https://discourse.julialang.org/u/droodman)\
**Post date:** [December 5, 2023, 9:44pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/13 "2023-12-05T21:44:58Z")

</div>

@GunnarFarneback, I did not know about this! It looks well done and is reassuring to me.

It appears that there is one novelty in what I have done, which might interest you. It flows entirely from the [guidance](https://github.com/JuliaLang/juliaup/issues/758#issuecomment-1836577702) of @staticfloat.

It’s a response to the problem that an application distributed without Julia has to find the shared Julia libraries somehow. The task is complicated by the multiplexing of juliaup, which tends to further obscure the location of the libraries, because there could be several locations, for different Julia versions simultaneously installed.

The solution is to run a shell command to look first for the executable, and ask it which libjulia it is using:

```julia
julia -e "using Libdl; println(dlpath(\"libjulia\"))" > tempfile

```

In my context, I have little choice to us use a temporary file to capture the library path. There are probably more graceful solutions in other contexts.

---

<div class="post-metadata">

**Author:** ![GunnarFarneback](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gunnarfarneback/32/1827_2.png) [@GunnarFarneback](https://discourse.julialang.org/u/GunnarFarneback)\
**Post date:** [December 5, 2023, 10:42pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/14 "2023-12-05T22:42:33Z")

</div>

So what my application does after the juliaup integration is the following (it’s a requirement that the users have juliaup installed):

1. Look up julia version from an application configuration file, for this example let’s assume it’s 1.9.3.
2. Run external process `juliaup add 1.9.3`.
3. Run external process `julia +1.9.3 -E Sys.BINDIR` and read the output into `bindir`.
4. Windows: `SetDllDirectoryW(bindir)`, `julia_library_name = "libjulia.dll"`
5. Linux: `bindir.replace("/bin", "/lib")`, `julia_library_name = bindir + "/libjulia.so"`
6. Continue with what’s already in DynamicallyLoadedEmbedding.

It would be nicer if I could just ask juliaup for the location of `libjulia` for a given version. It should have the needed information and be faster to query than spinning up a Julia process only for that reason.

---

<div class="post-metadata">

**Author:** ![davidanthoff](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/davidanthoff/32/223493_2.png) [@davidanthoff](https://discourse.julialang.org/u/davidanthoff)\
**Post date:** [December 6, 2023, 9:46pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/15 "2023-12-06T21:46:10Z")

</div>

> [@GunnarFarneback](#):
>
> It would be nicer if I could just ask juliaup for the location of `libjulia` for a given version.

Yes, agreed, we discussed a possible API for that in [Make Windows & Mac installation put Julia runtime libraries in path · Issue #758 · JuliaLang/juliaup · GitHub](https://github.com/JuliaLang/juliaup/issues/758).

The idea I had there was that you could essentially ask Juliaup “give me the libjulia that I should be using if X is my working folder”, and then Juliaup would look at all the overrides/defaults etc and figure out which Julia version to use. I think your use case might be a bit different, in that you want to control which Julia version to use somewhere in your apps config, right? So we should actually design the API to support that case as well.

---

<div class="post-metadata">

**Author:** ![GunnarFarneback](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gunnarfarneback/32/1827_2.png) [@GunnarFarneback](https://discourse.julialang.org/u/GunnarFarneback)\
**Post date:** [December 7, 2023, 7:29pm UTC](https://discourse.julialang.org/t/how-to-dynamically-embed-julia-in-a-windows-app/107133/16 "2023-12-07T19:29:20Z")

</div>

Yes, that’s right.