Qt moc failure without an error message

Question

So I'm pretty new to Qt, and I've just inherited a project from someone else who is also new to Qt. He isn't around this week btw. We are using Visual Studio 2008, and have the latest version of Qt installed(4.6.2).

The project builds on my coworker's machine fine, and I can get the project from svn and build it directly. But under any other circumstances it refuses to build on my machine, and it doesn't give me much of an explanation why. Even if I just do a 'build clean' and then a 'build' it doesn't work. Any slight modification will make it fail.

When I try to build the entire project I get the error message:

1>Moc'ing MatrixTypeInterface.h... 1>moc: Cannot create .\GeneratedFiles\Debug\moc_MatrixTypeInterface.cpp;.\GeneratedFiles\Debug\moc_matrixtypeinterface.cpp 1>Project : error PRJ0019: A tool returned an error code from "Moc'ing MatrixTypeInterface.h..."

The moc tool doesn't give any sort of error message as to why it isn't working, and I wasted most of yesterday trying to figure out why. I got the command that VS was using to call moc, and I entered in the command line myself. It didn't write anything to the screen.

Any ideas?

Answer 1

It's most likely a filesystem error, you probably don't have a "GeneratedFiles" folder or don't have the correct permissions on it.

I have had issues where different versions of the moc and the add-in use "Generated" or "Generated Files" or "GeneratedFiles" for the folder. Check the settings on all the build steps.

Answer 2

Its possible that your .vcproj file is corrupted. I've had this issue before which resulted from having different versions of Qt and the Qt VS add-on ended up corrupting my .vcproj files. For a while, I had to manually fix the .vcproj file (My AdditionalDependencies="..." line was being swapped around and cut off for various header files that needed to be mocced, I was manually fixing these for every new header that needed to be mocced).

A clean reinstall of Visual Studios + Qt + Qt add-on ended up fixing this. Check your .vcproj file and see if its making sense.

Answer 3

Are you sure your file paths are correct and existing before moc runs? Since it appears that relative paths are provided to moc, I'd find out what moc's working directory is when it runs.

How was your .vcproj file generated? Was qmake used? Or cmake? Or was it by scratch?

Answer 4

I finally found the answer. my coworker was back in the office today, and I used the build log off his machine to get his full moc command(about 4 lines long). Our moc commands were basically the same except at the very end. His command ended in:

-o ".\GeneratedFiles\$(ConfigurationName)\moc_$(InputName).cpp"

My command ended with:

-o ".\GeneratedFiles\$(ConfigurationName)\moc_$(InputName).cpp;.\GeneratedFiles\Debug\moc_matrixtypeinterface.cpp"

I checked the custom build step for that file, and removed the excess bit. After that the file compiled fine. I don't know how or why qt decided to add in this extra tidbit, but it did.

Thanks for your help guys. A couple of you suspected that it was a filesystem issue, and indeed a semicolon is not allowed in a windows filename. But I feel the root cause was Qt creating the wrong build string.

I'm accepting my own answer in the hope that it will help someone else.