# How can I add a dependent task to a task created by a C plugin? **URL:** \ **Category:** Help/Discuss\ **Created:** [April 17, 2019, 4:45pm UTC](https://discuss.gradle.org/t/how-can-i-add-a-dependent-task-to-a-task-created-by-a-c-plugin/31466 "2019-04-17T16:45:14Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![jeff6times7](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/jeff6times7/32/7552_2.png) [@jeff6times7](https://discuss.gradle.org/u/jeff6times7)\ **Post date:** [April 17, 2019, 4:45pm UTC](https://discuss.gradle.org/t/how-can-i-add-a-dependent-task-to-a-task-created-by-a-c-plugin/31466/1 "2019-04-17T16:45:15Z")
I have successfully created a build script to produce a native executable using the C plugin. I am stuck, though, in my attempt to create a dependency on a task that produces a flex output file from a flex input file. Here is what I believe to be the essential part of the build script. I’ve commented out my attempts to declare the dependency. ``` apply plugin: 'c' model { components { test(NativeExecutableSpec) { sources { c { source { srcDir "." include "*.c" } } } } } } task compileLang (type: Exec) { inputs.file(project.file('test.l')) outputs.file(project.file('lex.test.c')) commandLine 'flex', '-f', '-L', '-8', '-i', '-P', 'test', 'test.l' } //buildDependentsTestExecutable.dependsOn compileLang //project.task('buildDependentsTestExecutable').dependsOn compileLang //project.tasks.getByName('buildDependentsTestExecutable').dependsOn compileLang ``` Here are what I believe to be the relevant tasks configured when I execute ‘gradle tasks’: ``` Build tasks ----------- assemble - Assembles the outputs of this project. build - Assembles and tests this project. clean - Deletes the build directory. installTestExecutable - Installs a development image of executable 'test:executable' testExecutable - Assembles executable 'test:executable'. Build Dependents tasks ---------------------- assembleDependentsTest - Assemble dependents of native executable 'test'. assembleDependentsTestExecutable - Assemble dependents of executable 'test:executable'. buildDependentsTest - Build dependents of native executable 'test'. buildDependentsTestExecutable - Build dependents of executable 'test:executable'. ``` ---
**Author:** ![Comnir](https://avatars.discourse-cdn.com/v4/letter/c/a9adbd/32.png) [@Comnir](https://discuss.gradle.org/u/Comnir)\ **Post date:** [April 20, 2019, 2:18pm UTC](https://discuss.gradle.org/t/how-can-i-add-a-dependent-task-to-a-task-created-by-a-c-plugin/31466/2 "2019-04-20T14:18:39Z")
Can you describe how and what is not working? Do you get an error when you try any of those attempts to add the dependent task? ---
**Author:** ![jeff6times7](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/jeff6times7/32/7552_2.png) [@jeff6times7](https://discuss.gradle.org/u/jeff6times7)\ **Post date:** [April 20, 2019, 2:27pm UTC](https://discuss.gradle.org/t/how-can-i-add-a-dependent-task-to-a-task-created-by-a-c-plugin/31466/3 "2019-04-20T14:27:02Z")
When I uncomment the the first commented line [//buildDependentsTestExecutable.dependsOn](https://buildDependentsTestExecutable.dependsOn) compileLang then I see this: ``` $ gradle build FAILURE: Build failed with an exception. * Where: Build file '/Users/jholt/gradle/build.gradle' line: 24 * What went wrong: A problem occurred evaluating root project 'gradle'. > Could not get unknown property 'buildDependentsTestExecutable' for root project 'gradle' of type org.gradle.api.Project. * Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights. * Get more help at https://help.gradle.org BUILD FAILED in 0s ``` When I uncomment the 2nd commented line [//project.task](https://project.task)(‘buildDependentsTestExecutable’).dependsOn compileLang then I see this (indicating that it never executed the dependent task because there’s no lex.test.c that was created and included in the compiling and linking) ``` $ gradle build > Task :linkTestExecutable FAILED Undefined symbols for architecture x86_64: "_testwrap", referenced from: _main in test.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) FAILURE: Build failed with an exception. * What went wrong: Execution failed for task ':linkTestExecutable'. > A build operation failed. Linker failed while linking test. See the complete log at: file:///Users/jholt/gradle/build/tmp/linkTestExecutable/output.txt > Linker failed while linking test. * Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights. * Get more help at https://help.gradle.org BUILD FAILED in 0s 2 actionable tasks: 1 executed, 1 up-to-date ``` When I uncommented the 3rd commented line [//project.tasks.getByName](https://project.tasks.getByName)(‘buildDependentsTestExecutable’).dependsOn compileLang then I get the same error that I got when I uncommented the 1st commented line. ---
**Author:** ![jeff6times7](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/jeff6times7/32/7552_2.png) [@jeff6times7](https://discuss.gradle.org/u/jeff6times7)\ **Post date:** [April 20, 2019, 2:30pm UTC](https://discuss.gradle.org/t/how-can-i-add-a-dependent-task-to-a-task-created-by-a-c-plugin/31466/4 "2019-04-20T14:30:41Z")
Attached are the files in the directory. All you need to reproduce the critical part of my environment is gradle, a toolchain, and flex.[files.zip](https://discuss.gradle.org/uploads/short-url/yHbDZeMwHNeLXNorQNfCMuWJ0Gs.zip) (913 Bytes) ---
**Author:** ![jeff6times7](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/jeff6times7/32/7552_2.png) [@jeff6times7](https://discuss.gradle.org/u/jeff6times7)\ **Post date:** [April 20, 2019, 2:34pm UTC](https://discuss.gradle.org/t/how-can-i-add-a-dependent-task-to-a-task-created-by-a-c-plugin/31466/5 "2019-04-20T14:34:48Z")
Let me rephrase what I want. I have a project with a main c program that calls a lexical analyzer that is stored in a .l file. That .l file has to be converted into a .c file before the compilation takes place. That means the model has to be evaluated as if its source file is the .l file but that it has to run a filter to produce the lex.test.c file before compilation starts. And what I truly desire is something simple. I don’t want to have more than one build script as that would presumably increase the brittleness of the solution. I, in fact, already have a working solution that uses two build scripts and I hate it. ---
**Author:** ![Comnir](https://avatars.discourse-cdn.com/v4/letter/c/a9adbd/32.png) [@Comnir](https://discuss.gradle.org/u/Comnir)\ **Post date:** [April 20, 2019, 5:08pm UTC](https://discuss.gradle.org/t/how-can-i-add-a-dependent-task-to-a-task-created-by-a-c-plugin/31466/6 "2019-04-20T17:08:37Z")
Thanks for the example! The task seems to be created at a later phase of the Gradle’s configuration phase. I suggest adding a listener on the tasks container and it worked for me on your example: ``` project.tasks.whenObjectAdded { Task t -> println 'Task added: ' + t.name if ('buildDependentsTestExecutable'.equals(t.name)) { t.dependsOn compileLang } } ``` I’m not familiar with the ‘c’ plugin or with the model{} configuration, so my suggestion is based on the general familiarity I’ve with Gradle. ---
**Author:** ![jeff6times7](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/jeff6times7/32/7552_2.png) [@jeff6times7](https://discuss.gradle.org/u/jeff6times7)\ **Post date:** [April 20, 2019, 11:59pm UTC](https://discuss.gradle.org/t/how-can-i-add-a-dependent-task-to-a-task-created-by-a-c-plugin/31466/7 "2019-04-20T23:59:10Z")
“I’m not familiar” Me too and I’m betting we are members of a high cardinality set. Your suggestion works but I had to change the task name from ‘buildDependentsTestExecutable’ to ‘compileTestExecutableTestC’ before it worked fully. I tested the incremental build nature (i.e., changing test.c or test.l) and subsequent builds do the expected things and skips tasks when I expect them to be up-to-date and it executes them when I expect them not to be up-to-date. I missed methods returned by Project.getTasks (that returns a TaskContainer), that are inherited by org.gradle.api.DomainObjectCollection. I got frustrated by an apparently lack of attention at this site and asked an SO question. If you post your answer at [https://stackoverflow.com/q/55732834/1707353](https://stackoverflow.com/q/55732834/1707353), then I’ll accept it and upvote it and you’ll get the bounty.