Portability improvements to Boost Dependency

The Boost dependency has been improved to better detect the various ways to install boost on multiple platforms. At the same time the modules semantics for the dependency has been changed. Previously it was allowed to specify header directories as modules but it wasn't required. Now, modules are only used to specify libraries that require linking.

This is a breaking change and the fix is to remove all modules that aren't found.

Generator learned capture

Generators can now be configured to capture the standard output. See test cases/common/98 gen extra/meson.build for an example.

Can index CustomTarget objects

The CustomTarget object can now be indexed like an array. The resulting object can be used as a source file for other Targets, this will create a dependency on the original CustomTarget, but will only insert the generated file corresponding to the index value of the CustomTarget's output keyword.

c = custom_target(
  ...
  output : ['out.h', 'out.c'],
)
lib1 = static_library(
  'lib1',
  [lib1_sources, c[0]],
  ...
)
exec = executable(
  'executable',
  c[1],
  link_with : lib1,
)

Can override executables in the cross file

The cross file can now be used for overriding the result of find_program. As an example if you want to find the objdump command and have the following definition in your cross file:

[binaries]
...
objdump = '/usr/bin/arm-linux-gnueabihf-objdump-6'

Then issuing the command find_program('objdump') will return the version specified in the cross file. If you need the build machine's objdump, you can specify the native keyword like this:

native_objdump = find_program('objdump', native : true)

Easier handling of supported compiler arguments

A common pattern for handling multiple desired compiler arguments, was to test their presence and add them to an array one-by-one, e.g.:

warning_flags_maybe = [
  '-Wsomething',
  '-Wanother-thing',
  '-Wno-the-other-thing',
]
warning_flags = []
foreach flag : warning_flags_maybe
  if cc.has_argument(flag)
    warning_flags += flag
  endif
endforeach
cc.add_project_argument(warning_flags)

A helper has been added for the foreach/has_argument pattern, so you can now simply do:

warning_flags = [ ... ]
flags = cc.get_supported_arguments(warning_flags)

Better support for shared libraries in non-system paths

Meson has support for prebuilt object files and static libraries. This release adds feature parity to shared libraries that are either in non-standard system paths or shipped as part of your project. On systems that support rpath, Meson automatically adds rpath entries to built targets using manually found external libraries.

This means that e.g. supporting prebuilt libraries shipped with your source or provided by subprojects or wrap definitions by writing a build file like this:

project('myprebuiltlibrary', 'c')

cc = meson.get_compiler('c')
prebuilt = cc.find_library('mylib', dirs : meson.current_source_dir())
mydep = declare_dependency(include_directories : include_directories('.'),
                           dependencies : prebuilt)

Then you can use the dependency object in the same way as any other.

wrap-svn

The Wrap dependency system now supports Subversion (svn). This support is rudimentary. The repository url has to point to a specific (sub)directory containing the meson.build file (typically trunk/). However, providing a revision is supported.