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New post: debugging golang app on a fedora atomic desktop
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‎content/posts/06-golang-debugging-on-fedora-atomic.md‎

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title: Debuging a Golang project on a Fedora Atomic Desktop (with Emacs and Dape)
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---
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A couple months ago, I tried to get [Dape](https://github.com/svaante/dape) working with a Golang project and ran into a couple of problems that prevented me from being able to use it. Today I decided to revisit it, and I'm glad I did, because it was one of the last remaining reasons I had for ever needing to open VSCode.
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## First attempt at using Dape with a Golang project
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### Problem 1 - passing arguments
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In the top-level of my repo, I created the file `.dir-locals.el` with the following content:
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```lisp
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((go-mode . ((dape-configs .
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((go-debug-main
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modes (go-mode go-ts-mode)
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command "dlv"
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command-args ("dap" "--listen" "127.0.0.1:55878" "--log-dest" "/tmp/dlv.log")
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command-cwd "/home/shanemcd/github/GoogleContainerTools/skaffold/examples/simple-artifact-dependency"
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host "127.0.0.1"
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port 55878
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:request "launch"
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:mode "debug"
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:type "go"
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:showLog "true"
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:program "/home/shanemcd/github/GoogleContainerTools/skaffold/cmd/skaffold/skaffold.go"
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:args ("build")))))))
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```
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I am using Google's [Skaffold](https://skaffold.dev/) here in my example, but any program that accepts command line arguments will serve the purpose.
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With this config in place, I navigated to the program's entrypoint (`cmd/skaffold/skaffold.go`) and was prompted with this:
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```
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The local variables list in /home/shanemcd/github/GoogleContainerTools/skaffold/
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or .dir-locals.el contains values that may not be safe (*).
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Do you want to apply it? You can type
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y -- to apply the local variables list.
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n -- to ignore the local variables list.
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! -- to apply the local variables list, and permanently mark these
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values (*) as safe (in the future, they will be set automatically.)
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i -- to ignore the local variables list, and permanently mark these
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values (*) as ignored
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+ -- to apply the local variables list, and trust all directory-local
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variables in this directory
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* dape-configs : ((go-debug-main modes (go-mode go-ts-mode) command "dlv" command-args ("dap" "--listen" "127.0.0.1:55878" "--log-dest" "/tmp/dlv.log") command-cwd "/var/home/shanemcd/github/GoogleContainerTools/skaffold/examples/simple-artifact-dependency" host "127.0.0.1" port 55878 :request "launch" :mode "debug" :type "go" :showLog "true" :program "/var/home/shanemcd/github/GoogleContainerTools/skaffold/cmd/skaffold/skaffold.go" :args ("build")))
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```
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After typing `y` and pressing `Return`. With the file open, I then ran `M-x dape` and saw the following output in the `*dape-repl*` buffer:
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```
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* Welcome to Dape REPL! *
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Available Dape commands: debug, next, continue, pause, step, out, up, down, threads, stack, modules, sources, breakpoints, scope, watch, restart, kill, disconnect, quit
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Empty input will rerun last command.
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* Process launched /var/home/shanemcd/github/GoogleContainerTools/skaffold/examples/simple-artifact-dependency/__debug_bin1126826703 *
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Type 'dlv help' for list of commands.
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Hello
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A tool that facilitates continuous development for Kubernetes applications.
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Find more information at: https://skaffold.dev/docs/getting-started/
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End-to-end Pipelines:
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run Run a pipeline
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dev Run a pipeline in development mode
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debug Run a pipeline in debug mode
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Pipeline Building Blocks:
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build Build the artifacts
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test Run tests against your built application images
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deploy Deploy pre-built artifacts
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delete Delete any resources deployed by Skaffold
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render Generate rendered Kubernetes manifests
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apply Apply hydrated manifests to a cluster
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verify Run verification tests against skaffold deployments
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Getting Started With a New Project:
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init Generate configuration for deploying an application
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Other Commands:
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completion Output shell completion for the given shell (bash, fish or zsh)
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config Interact with the global Skaffold config file (defaults to `$HOME/.skaffold/config`)
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diagnose Run a diagnostic on Skaffold
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exec Execute a custom action
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fix Update old configuration to a newer schema version
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schema List JSON schemas used to validate skaffold.yaml configuration
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survey Opens a web browser to fill out the Skaffold survey
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version Print the version information
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Usage:
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skaffold [flags] [options]
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Use "skaffold <command> --help" for more information about a given command.
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Use "skaffold options" for a list of global command-line options (applies to all commands).
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```
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Well, that didn't work as I had expected.
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Reading over the `dape` README, I saw this under the `C, C++ and Rust - lldb-dap` heading:
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> To pass arguments, use `:args ["arg1" "arg2" ..]`
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At first I did not try this because I assumed if it also applied to other languages it would have been called out explicitly, but sure enough, it worked after running `dape` and then appending my args:
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```
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go-debug-main :args ["build"]
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```
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I then tried to update my `.dir-locals.el` with the bracket notation:
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```diff
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diff --git a/.dir-locals.el b/.dir-locals.el
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index 65e164b..9995c3a 100644
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--- a/.dir-locals.el
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+++ b/.dir-locals.el
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@@ -11,4 +11,4 @@
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          :type "go"
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          :showLog "true"
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          :program "/home/shanemcd/github/GoogleContainerTools/skaffold/cmd/skaffold/skaffold.go"
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-          :args ("build")))))))
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+          :args ["build"]))))))
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```
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... and it worked! 🎉 (but also🤦‍♂️)
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```
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* Welcome to Dape REPL! *
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Available Dape commands: debug, next, continue, pause, step, out, up, down, threads, stack, modules, sources, breakpoints, scope, watch, restart, kill, disconnect, quit
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Empty input will rerun last command.
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* Process launched /var/home/shanemcd/github/GoogleContainerTools/skaffold/examples/simple-artifact-dependency/__debug_bin2338563526 build *
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Type 'dlv help' for list of commands.
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Generating tags...
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- app -> app:v2.15.0-4-g8c00b98d7
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- base -> base:v2.15.0-4-g8c00b98d7
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Checking cache...
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- app: Not found. Building
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- base: Not found. Building
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Starting build...
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Building [base]...
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Sending build context to Docker daemon 3.072kB
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Step 1/3 : FROM alpine:3
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---> aded1e1a5b37
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Step 2/3 : COPY hello.txt .
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---> Using cache
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---> 5739d7557ae4
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Step 3/3 : CMD ["./app"]
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---> Using cache
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---> 17979f81cffb
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Successfully built 17979f81cffb
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Successfully tagged base:v2.15.0-4-g8c00b98d7
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The push refers to repository [docker.io/library/base]
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23deea18e759: Preparing
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08000c18d16d: Preparing
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Process 160667 has exited with status 1
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Detaching
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* Session terminated *
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```
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### Problem 2 - breakpoints not working
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Now with the command invocation working, I proceeded with trying to set a breakpoint in the Skaffold code with `dape-breakpoint-toggle C-x C-a b`. Doing that and then re-running `dape`, I was surprised to see that the breakpoint did not hit as I was expecting.
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After describing my problem to ChatGPT, it inferred from our previous chats that I was using Fedora Kinoite, and it pointed out right away that symlinks (Fedora Atomic Desktops link `/home/` to `/var/home`) were known to cause problem in debuggers. After a quick search, that was easy to confirm after locating [this note](https://github.com/golang/vscode-go/blob/master/docs/debugging.md#debug-symlink-directories) in the `vscode-go` docs. I was able to get around this by setting `HOME` to the full path when in my `.dir-locals.el`
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```diff
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diff --git a/.dir-locals.el b/.dir-locals.el
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index 9995c3a..fba8c9f 100644
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--- a/.dir-locals.el
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+++ b/.dir-locals.el
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@@ -3,12 +3,12 @@
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          modes (go-mode go-ts-mode)
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          command "dlv"
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          command-args ("dap" "--listen" "127.0.0.1:55878" "--log-dest" "/tmp/dlv.log")
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-          command-cwd "/home/shanemcd/github/GoogleContainerTools/skaffold/examples/simple-artifact-dependency"
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+          command-cwd "/var/home/shanemcd/github/GoogleContainerTools/skaffold/examples/simple-artifact-dependency"
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          host "127.0.0.1"
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          port 55878
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          :request "launch"
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          :mode "debug"
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          :type "go"
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          :showLog "true"
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-          :program "/home/shanemcd/github/GoogleContainerTools/skaffold/cmd/skaffold/skaffold.go"
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+          :program "/var/home/shanemcd/github/GoogleContainerTools/skaffold/cmd/skaffold/skaffold.go"
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          :args ["build"]))))))
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```
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And when launching emacs:
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```
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$ env HOME=/var/home/shanemcd emacs
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```
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Seeking a more long-term solution, I was able to add this to my emacs configuration, which handles setting `HOME` correctly whenever it is symlinked:
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```lisp
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(when-let ((real-home (file-truename (getenv "HOME"))))
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(when (not (string= (getenv "HOME") real-home))
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(setenv "HOME" real-home)))
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```
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I still have a lot more to learn, but with this, I am at least able to set breakpoints in my Golang application, step through the code, and inspect variables. I hope this blog post proves to be useful for others, but if nothing else I will be able to copy + paste these configs the next time I lose them. 🙂

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