Error "/usr/bin/ld: cannot find library: File format not recognized" when application is built as part of a collection of products

Question

I have a QBS Project which is a collection of subprojects, including static libraries, shared libraries, and a Qt GUI applications. The Qt GUI application has been giving me issue in that the linking stage fails, throwing several "/usr/bin/ld: cannot find {library}: File format not recognized" errors for libraries that are built earlier in the project chain. It does not do this for all libraries though, including libraries with near identical .qbs files as those which do throw this error.

Oddly enough, if I build the application on it's own, that is to say I run qbs from within the application's project directory rather than at the top level, it builds fine (assuming the dependent libraries all exist within their install directories). The main difference I see is that when building the full project, the cpp.libraryPaths for the application are ignored for all products in the project and the application attempts to link against the lib files produced in the build directory, while when building the application on it's own the cpp.libraryPaths are used as intended, and the files in the install directory are linked against successfully.

I have no idea why the lib files in the install directory can be linked against while files in the build directory throw errors. What could be causing the linking to fail in the first place? Additionally, how can I fix my project configuration so that I can build everything by calling qbs at the top level. Am I perhaps going about this in the wrong manner?

Here is the command I use to start the build:

qbs qbs.installRoot:. release

And a visual representation of the issue:

Poject         <-- calling qbs here throws errors at linking application
|- LibraryOne
|- LibraryTwo
|- Application <-- calling qbs here works if libraries already built

And here is a very simplified reproduction of the relevent qbs files

-- SubOne.qbs and SubTwo --
// These are identical excluding the files

StaticLibrary {
    name: // "One" or "Two"
    files: [/*Files...*/]

    Depends { 
        name: "Qt"
        submodules: [/*core, etc...*/]
    }

    Depends { name: "cpp" }

    // cpp depends and properties   

    Group {
        fileTagsFilter: product.type
        qbs.installDir: "lib"
        qbs.install: true
    }
}

-- App.qbs --

QtGuiApplication {
    name: "App"
    files: [/*Files...*/]

    Depends { name: "One" } // I comment out these depends when building the Application on it's own
    Depends { name: "Two" }

    Depends { name: "cpp" }
    cpp.includePaths: ["../One/include","..Two/include"]
    cpp.libraryPaths: ["../lib"] // <-- Ignored during full project build
    cpp.staticLibraries: ["One","Two"]

    Group {
        fileTagsFilter: product.type
        qbs.installDir: "bin"
        qbs.install: true
    }
}

Answer 1

Never run qbs from a subdirectory. You should always run it on the top-level project file. In your root directory you should have a file like this:

// project.qbs
import qbs

Project {
    // order doesn't matter here
    references: [
        "LibraryOne/SubOne.qbs",
        "LibraryTwo/SubTwo.qbs",
        "Application/App.qbs"
    ]
}

Secondly, you should not set the cpp.libraryPaths and cpp.staticLibraries in your application, as the Depends items which you have in your application, will already handle this (never comment them out).

Your cpp.includePaths properties should also not be set in the application, instead they should go into an Export item in each of your respective static libraries, like so:

StaticLibrary {
    ...
    Export {
        Depends { name: "cpp" }
        cpp.includePaths: [product.sourceDirectory + "/include"]
    }
    ...
}

Then run qbs -f project.qbs and everything should be built correctly.