Qbs Quick Reference

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On October 29th, 2018, The Qt Company announced that Qbs is deprecated.

Introduction

Qbs is the next-generation build system "initially introduced in the Qt Labs Blog. This page is intended as a quick guide to porting project files from qmake .pro syntax to .qbs. It is not intended to supplant the official documentation, rather to be a quick summary of the current status of qbs functionality with a focus on how to port from qmake.

Some things at the time of writing have no equivalent qbs syntax. Bugtracker links are included for missing functionality, where known.

Qbs Manual

The full Qbs Manual is found at http://doc.qt.io/qbs

Migrating from other build systems

For up-to-date information, see:

Migrating from qmake

.pro and .pri

The top-level .qbs file contains the "Project" definition. A project can contain multiple products, so you may find that multiple .pro files can be expressed in a single .qbs. The subdirs pattern will typically convert to a single .qbs containing references to multiple .qbs files. Each .qbs file would then define a single product or sub-project.

.qbs files can also be used like .pri files in that a top-level .qbs can include sections defined in another .qbs. For example:

/* CrazyProduct.qbs */
import qbs.base 1.0

Product {
  property string craziness: "low"
}

/* hellocrazyworld.qbs */
CrazyProduct {
  craziness: "enormous"
  name: "hellocrazyworld"
  // …
}

.qbs files in the same directory as the top-level .qbs file are picked up automatically. Others must be explicitly imported and named using an "import … as …" statement:

import qbs.base 1.0
import "../CrazyProduct.qbs" as CrazyProduct

CrazyProduct {
  craziness: "enormous"
  name: "hellocrazyworld"
  // …
}

It is also possible pick groups of source files externally like with .pri files, by importing a .qbs with a Group defined in it and declaring this imported group inside the Product declaration.

/* external.qbs */
import qbs
Group {
  files: ["file1.cpp", "file2.cpp"]
}

/* product.qbs */
import qbs
import "external.qbs" as SourceGroup

Product {
  name: "SomeProduct"
  SourceGroup {}
}

If opened with qtcreator, files from external.qbs will be visible in a group belonging to SomeProduct

Conditionals

Instead of the qmake syntax of "windows { … }" or "macx:…", you specify a "condition" property in the relevant block. Conditionally-compiled files should be collected in a "Group" block, while platform-specific properties should go in a "Properties" block rather than being put in the main (outer) block:

Group {
  condition: qbs.targetOS.contains("windows")
  files: [
    "harddiskdeleter_win.cpp",
    "blowupmonitor_win.cpp",
    "setkeyboardonfire_win.cpp"
  ]
}

Properties {
  condition: qbs.targetOS.contains("linux")
  cpp.defines: outer.concat(["USE_BUILTIN_DESTRUCTORS"])
}

See the DEFINES section above for important information about how conditionals and cpp.defines interact.

C++ compiler options

Here is a selection of options that are supported. The full list can be found in share/qbs/modules/cpp/CppModule.qbs in the qbs source tree, these are some of the more useful:

cpp.optimization: "none" // or "fast"
cpp.debugInformation: true
cpp.staticLibraries: "libraryName"
cpp.dynamicLibraries: "libraryName"
cpp.frameworks: "frameworkName"
cpp.precompiledHeader: "myheader.pch"
cpp.warningLevel: "all" // or "none", "default"
cpp.treatWarningsAsErrors: true
cpp.cxxLanguageVersion // E.g. "c++11"

Note that setting things like cflags directly is discouraged (because they are compiler-dependent), and higher-level alternatives like cpp.optimization: "fast" should be used if available.

Installing files

Create a group containing the files, and set qbs.install and qbs.installDir:

Group {
  qbs.install: true
  qbs.installDir: "lib/myproj/"
  files: [
    "Menu.qml",
    "SomeImportantFile.bin"
  ]
}

For files generated by the build (e.g. an executable), you need to match them by their file tag:

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

By default, installation happens automatically when building. The default installation root is called "install_root" and is located at the top level of the build directory. It can be overwritten by setting the qbs.installRoot property on the command line.

Command-line examples

64-bit:

$ qbs -f /path/to/project.qbs --products productname qbs.architecture:x86_64

"Magic" variables

Variables defined in various scopes, which may not be obvious:

qbs

This has lots of useful things in, such as: targetOS ("windows", "linux", "darwin", …); buildVariant ("debug", "release"); architecture ("x86", "x86_64", …)

project

Valid anywhere in your project, needed to refer to project properties from within a product:

Project {
  property string version: "1.0"

  Product {
    cpp.defines: ["PROJECT_VERSION=" + project.version]
  }
}

buildDirectory

The top-level build directory. By default will be a subdirectory in the directory where you invoked qbs from, whose name is derived from the current profile. It can also be explicitly specified via the -d option.

Module names

Modules that are declared as dependencies can be referred to by their name and their properties accessed. For example:

Product {
  Depends { name: "Qt.quick" }
  Qt.quick.qmlDebugging: false
}