CDT Editor shows errors but project builds successfully

[gregwillits]

Eclipse: 2025-03 (4.35.0) Build id: 20250306-0812
macOS 15.5

A project is showing "unresolved inclusion" marks in the gutter to the left of the line numbers, and then showing errors for any code involved (e.g. can't find stdbool, and shows errors in the editor (but not in the Console build log) for every use of bool, true, false, etc.)

And yet... the project builds and runs just fine.

I don't know if the below activity is related or not (mighty suspicious timing), but either way something broke.

Late yesterday, In order to fix a problem with brew/ruby-build and building ruby 3.4.4, I ended up deleting an old CommandLineTools install at /Library/Developer/CommandLineTools. Since I had the full XCode install anyway, the building of ruby apparently used that, and it worked.

Meanwhile I ended up updating to XCode 16.4 as well. It's working fine.

Now today, Eclipse appears to have no idea where to find many (all?) of the standard C libraries. My project will "build" but there's 40 billion errors showing in the editor across virtually all files. Note that the error icon overlays don't appear in the Project Explorer on a given file until after the file is opened in the editor (where normally real errors are badged whather a file is opened or not).

I tried these things:

• clean project, reindex, etc.
• a different project — which works, so this does seem to be a project-specific thing, not universal.
• reverting to a previous commit
• google. no luck yet.
• I reinstalled an updated CommandLineTools thinking maybe Eclipse was using that. No joy.
• I renamed my existing Eclipse, and installed a fresh clean copy. No joy.

I compared the C/C++ Build and General settings (all tabs) to a working project, and I can't find any differences.

I could use some hints as to what else to look into.

Apologies, for distracting you from real problems.

Thanks for your time.

[jonahgraham]

Apologies, for distracting you from real problems.

Seems like a real problem to me :-)

Did you reuse the workspace when you tried a new fresh copy of Eclipse? If not, try importing the project into a new workspace. Alternatively you can do a localized cleanup. With Eclipse closed, delete .metadata/.plugins/org.eclipse.cdt.core/name.*

[gregwillits]

SCHWEET! Yes, deleting the metedata files for the project worked. All good again.

And now that I think about it, a better title for future people to find would have been "CDT Editor shows errors but project builds successfully" or something like that.

[jonahgraham]

Thanks @gregwillits for reporting back.

I added an entry into the FAQ https://github.com/eclipse-cdt/cdt/blob/main/FAQ/Indexer.md#indexer-shows-errors-on-a-project-that-previously-worked and I am going to convert this issue into a discussion.

If in the future you have a reproducible test case for this issue, please file a new bug.