# How to edit source code of Julia

**URL:** <https://discourse.julialang.org/t/how-to-edit-source-code-of-julia/19156>\
**Category:** General Usage\
**Created:** [December 31, 2018, 9:04pm UTC](https://discourse.julialang.org/t/how-to-edit-source-code-of-julia/19156 "2018-12-31T21:04:20Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![affans](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/affans/32/11911_2.png) [@affans](https://discourse.julialang.org/u/affans)\
**Post date:** [December 31, 2018, 9:04pm UTC](https://discourse.julialang.org/t/how-to-edit-source-code-of-julia/19156/1 "2018-12-31T21:04:20Z")

</div>

I believe I may have found a bug in Julia source code but I can’t pinpoint the exact line ([see this topic])([There is a bug in this function and I can't figure out what it is](https://discourse.julialang.org/t/there-is-a-bug-in-this-function-and-i-cant-figure-out-what-it-is/19150)). What I want to do is modify the `Distributed.jl` module in Julia source code so that whenever I write `using Distributed` (or when a pacakge called `using Distributed`) my edited code is used.

This is what I’ve done so far. I’ve taken the actual source code files from Julia source and copied them into a new folder. Then I `include` this folder and call `using .Distributed`.

```julia
using Revise
includet("Distributed.jl")
using .Distributed
using ClusterManagers

a = addprocs(SlurmManager(2))

```

However, this dosnt work since `ClusterManagers` also does a `using Distributed` call and so it turns out that my edited `Distributed != ClusterManagers.Distributed`.

Is the only way to edit the Julia source code and recompile?

---

<div class="post-metadata">

**Author:** ![mauro3](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mauro3/32/292_2.png) [@mauro3](https://discourse.julialang.org/u/mauro3)\
**Post date:** [January 1, 2019, 10:56am UTC](https://discourse.julialang.org/t/how-to-edit-source-code-of-julia/19156/2 "2019-01-01T10:56:17Z")

</div>

You should build Julia from source. Then edit the file in question and do:

```julia
using Revise, Distributed
Revise.track(Distributed)
# check that it works

```

If it works, then rebuild Julia to bake the changes into the system-image. (And contribute your fix upstream with a PR).

I don’t know if there are ways to easily do this when you’re using the Julia binaries.

---

<div class="post-metadata">

**Author:** ![affans](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/affans/32/11911_2.png) [@affans](https://discourse.julialang.org/u/affans)\
**Post date:** [January 1, 2019, 3:05pm UTC](https://discourse.julialang.org/t/how-to-edit-source-code-of-julia/19156/3 "2019-01-01T15:05:58Z")

</div>

@mauro3 Thanks. I do this see in this documentation ([System Image Building · The Julia Language](https://docs.julialang.org/en/v1/devdocs/sysimg/))

But just a few clarification steps. I would need to build the system image on my cluster where I don’t have root access and everything will need to be done in my home directory. Is this possible?

I also don’t want to mess with the existing Julia binary installation nor its packages (it’s a cluster with 18 nodes using inifiniband and so the the same binary is installed on all 18 nodes).

Is there a way to rebuild `Base` into a library and use the existing Julia binary installed systemwide (clusterwide) to call that shared library?

---

<div class="post-metadata">

**Author:** ![mauro3](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mauro3/32/292_2.png) [@mauro3](https://discourse.julialang.org/u/mauro3)\
**Post date:** [January 1, 2019, 3:15pm UTC](https://discourse.julialang.org/t/how-to-edit-source-code-of-julia/19156/4 "2019-01-01T15:15:51Z")

</div>

The bug, I’d try to find on a local install, if at all possible.

Looks like you’re just updating one function. Then you can easily redefine the method in question by hand:

```julia
Distributed.message_handler_loop(r_stream::IO, w_stream::IO, incoming::Bool) = println("This version does nothing")

```

and make sure that the update is evaluated on all nodes. (Note sure how Revise would work on several nodes, could be tricky.)

---

<div class="post-metadata">

**Author:** ![affans](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/affans/32/11911_2.png) [@affans](https://discourse.julialang.org/u/affans)\
**Post date:** [January 1, 2019, 3:19pm UTC](https://discourse.julialang.org/t/how-to-edit-source-code-of-julia/19156/5 "2019-01-01T15:19:12Z")

</div>

I tried that but there are functions in `Distributed` that use global variables defined in the `Distributed` module. Everytime I redefine the function, it complains that the global variable is not found. I suppose when I redefine the function by `import Distributed.message_handler_loop` it actually brings it into `Main` where the global variable is not defined.

I also realized that `Distributed` is not in Base but rather in stdlib. I wonder if the process of rebuilding `stdlib` is the same as rebuilding `Base`.

---

<div class="post-metadata">

**Author:** ![mauro3](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mauro3/32/292_2.png) [@mauro3](https://discourse.julialang.org/u/mauro3)\
**Post date:** [January 1, 2019, 3:32pm UTC](https://discourse.julialang.org/t/how-to-edit-source-code-of-julia/19156/6 "2019-01-01T15:32:07Z")

</div>

Ok, then use `eval` to directly evaluate code inside a module:

```julia
julia> @eval Distributed message_handler_loop(r_stream::IO, w_stream::IO, incoming::Bool) = println("This version does nothing")
message_handler_loop (generic function with 1 method)

julia> Distributed.message_handler_loop(stdout, stdout, true)
This version does nothing

```

Again, make sure to do this on all nodes with `@everywhere`.

---

<div class="post-metadata">

**Author:** ![affans](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/affans/32/11911_2.png) [@affans](https://discourse.julialang.org/u/affans)\
**Post date:** [January 1, 2019, 4:19pm UTC](https://discourse.julialang.org/t/how-to-edit-source-code-of-julia/19156/7 "2019-01-01T16:19:19Z")

</div>

Thanks. I’ll try that.

Side note: I can’t use `@everywhere` since the bug is preventing the system to spawn and connect to the workers properly. It is `addprocs()` that bugs out.