Core Build Makefile project ignores custom working directory if build output location is "Build in project directory"

[i-garrison]

I would like to have dedicated build directory for Core Build Makefile project. I want a specific name build inside project directory and would not like to use make.run.linux.x86_64.Local which is used by launch configuration. I'm trying to do this via Launchbar Edit Configuration:

• Tab Build Settings section Build Output Location select Build in project directory
• Tab Arguments section Working directory uncheck Use default and set desired ${workspace_loc:myproject}/build

Steps to reproduce the behavior: Configure build settings and working directly as above and click Build button

Expected behavior
Working directory override setting takes precedence over default project directory.
make runs Building in: /full/path/to/myproject/build

Actual behavior
Working directory override is ignored and default project directory is used.
make runs Building in: /full/path/to/myproject

Note if I select Build in configuration specific directory and set Working directory to ${workspace_loc:myproject}/build, then override takes precedence and make runs Building in: /full/path/to/myproject/build/make.run.linux.x86_64.Local

EDIT: I'm confused about actual behavior, since when I tried more combinations and selected Build in configuration specific directory while setting Working directory to different one ${workspace_loc:myproject}/bbb it would stick to Building in: /full/path/to/myproject/build so it appears that it ignores the override there too?

Version Information:

• OS Linux
• Eclipse Version: 2025-09
• CDT Version: 12.2.0

[ewaterlander]

Hi @i-garrison

The working directory in the Arguments tab is the directory where the binary is launched from. Not the directory where the binary is built. This is true for all type of projects.

If you select in the Build Settings tab build in project directory, the build command will run in the top project directory.

If you wish to run make in a custom subfolder (for instance directory build), select build in project directory and change the Build command to: make -C build.

[i-garrison]

Hi @ewaterlander I just did as instructed and do not think Core Build Makefile worked as expected. After setting Build command to make -C build I found the following behavior:

1. At first, if I project from clean state (like by restart Eclipse CDT process, or just by closing/opening project from Project Explorer) it is able to complete the build successfully;
2. Unfortunately if I run the build and interrupt it in the middle it starts doing funny things like starting build inside a subdirectory and I cannot get it back to cleanstate unless I reopen project from clean state again. Currently I'm using Eclipse CDT with GDB the GNU debugger source code so there are a lot of things to compile and there is a great chance that if you stop build process it ends up in this funny state.

It looks like core build wants to continue building incrementally by descending to a directory it learned some time before I click Build button, but that now surely fails since make -C build is not valid for any subdirectory inside ${workspace_loc:myproject}/build. I'm also not able to find any do not do any incremental build setting which would probably be a workaround.

There is also strange behavior with compiler detection; on my system ccache is used via usual symlinks: gcc is /usr/lib/ccache/bin/gcc and g++ is /usr/lib/ccache/bin/g++
In this scenario this code snippet in GCCToolChain fails:

			if (command.toString().contains("ccache")) { //$NON-NLS-1$
				command = Paths.get(commandStrings.get(++offset));
			}

ending up with skipping to first compiler argument, and then it does not expect that there is no compiler name in the command:

java.lang.NullPointerException: Cannot obtain full command path for command -c
	at org.eclipse.cdt.build.gcc.core.GCCToolChain.getScannerInfo(GCCToolChain.java:285)
	at org.eclipse.cdt.core.build.CBuildConfiguration.processLine(CBuildConfiguration.java:939)

Guess until that is fixed I will not be able to check if Core Build Makefile is able to detect C++ language by parsing compiler output since it is missing the compiler.

[ewaterlander]

I do not know why the build ends in a funny state if you interrupt it in the middle. I will try myself. And also look at the compiler detection.

I do see the need to specify a custom build location, like is also possible with the classic managed projects . Only the project directory is not flexible enough.

Incremental build can be disabled in the Main tab of the launch configuration by selecting Disable auto build. When selected, builds will only start if you press the build button.