Managing build configurations

In this tutorial, you will learn how to use several build configurations with the same sources.

The problem

Let’s say you have a foo library, with some tests. You want to make the compilation of the tests optional (because they depend on gtest, and you do not want to force your users to have gtest).

A standard CMake way to do it would be:

option(WITH_GTEST "Enable compilation of unit tests" OFF)
if(WITH_GTEST)
  find_package(GTest Required)
# ...
  add_test(...)
else()
# ...
endif()

So far so good.

But now you have to pass “-DWITH_GTEST=ON” to all your projects when you configure them.

Note that there is a shortcut for that in qibuild CMake API using qi_add_optional_package:

qi_add_optional_package(GTEST)
if(GTEST)
# ....
else()
# ...
endif()

Here, if GTEST is not found, no error is raised, and WITH_GTEST is simply set to “OFF”...

But let’s assume you really need some flags.

Passing CMake flags with qiBuild

There are several ways to pass CMake flags to a project managed by qiBuild, in ascending priority:

• Just once

Simply call:

$ qibuild configure foo -DWITH_GTEST=ON

• You may want to trigger some flags depending on the toolchain / configuration you use.

  For instance, if you want to pass -DWITH_FOO=OFF when you are using the toolchain mingw32, you can write something like:

set(WITH_FOO OFF CACHE INTERAL "" FORCE)

in .qi/mingw32.cmake

Using build configurations

qiBuild also lets you to have different settings depending on the toolchain you use.

The config file will always be found in .config/qi/qibuild.xml

For instance, you could have on a windows machine:

<qibuild version="1">
  <defaults>
    <!-- some defaults -->
  </defaults>

  <config name="mingw32">
    <cmake generator="MinGW Makefiles" />
    <env path="c:\MinGW\bin" />
  </config>

  <config name="win32-vs2010">
    <cmake generator="Visual Studio 10" />
  </config>
</qibuild>