Persistent native environments

New in 0.49.0

Meson has cross files for describing cross compilation environments, for describing native environments it has equivalent "native files".

Natives describe the build machine, and can be used to override properties of non-cross builds, as well as properties that are marked as "native" in a cross build.

There are a couple of reasons you might want to use a native file to keep a persistent environment:

  • To build with a non-default native tool chain (such as clang instead of gcc)
  • To use a non-default version of another binary, such as yacc, or llvm-config

Changing native file settings

All of the rules about cross files and changed settings apply to native files as well, see here

Defining the environment

Binaries

Currently the only use of native files is to override native binaries. This includes the compilers and binaries collected with find_program, and those used by dependencies that use a config-tool instead of pkgconfig for detection, like llvm-config

[binaries]
c = '/usr/local/bin/clang'
cpp = '/usr/local/bin/clang++'
rust = '/usr/local/bin/rust'
llvm-config = '/usr/local/llvm-svn/bin/llvm-config'

Paths and Directories

As of 0.50.0 paths and directories such as libdir can be defined in the native file in a paths section

[paths]
libdir = 'mylibdir'
prefix = '/my prefix'

These values will only be loaded when not cross compiling. Any arguments on the command line will override any options in the native file. For example, passing --libdir=otherlibdir would result in a prefix of /my prefix and a libdir of otherlibdir.

Loading multiple native files

Native files allow layering (cross files can be layered since meson 0.52.0). More than one native file can be loaded, with values from a previous file being overridden by the next. The intention of this is not overriding, but to allow composing native files.

For example, if there is a project using C and C++, python 3.4-3.7, and LLVM 5-7, and it needs to build with clang 5, 6, and 7, and gcc 5.x, 6.x, and 7.x; expressing all of these configurations in monolithic configurations would result in 81 different native files. By layering them, it can be expressed by just 12 native files.

Native file locations

Like cross files, native files may be installed to user or system wide locations, defined as:

  • $XDG_DATA_DIRS/meson/native (/usr/local/share/meson/native:/usr/share/meson/native if $XDG_DATA_DIRS is undefined)
  • $XDG_DATA_HOME/meson/native ($HOME/.local/share/meson/native if $XDG_DATA_HOME is undefined)

The order of locations tried is as follows:

  • A file relative to the local dir
  • The user local location
  • The system wide locations in order

These files are not intended to be shipped by distributions, unless they are specifically for distribution packaging, they are mainly intended for developers.

The results of the search are