The Meson Build System
http://mesonbuild.com/
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
243 lines
8.3 KiB
243 lines
8.3 KiB
--- |
|
short-description: Dependencies for external libraries and frameworks |
|
... |
|
|
|
# Dependencies |
|
|
|
Very few applications are fully self-contained, but rather they use |
|
external libraries and frameworks to do their work. Meson makes it |
|
very easy to find and use external dependencies. Here is how one would |
|
use the zlib compression library. |
|
|
|
```meson |
|
zdep = dependency('zlib', version : '>=1.2.8') |
|
exe = executable('zlibprog', 'prog.c', dependencies : zdep) |
|
``` |
|
|
|
First Meson is told to find the external library `zlib` and error out |
|
if it is not found. The `version` keyword is optional and specifies a |
|
version requirement for the dependency. Then an executable is built |
|
using the specified dependency. Note how the user does not need to |
|
manually handle compiler or linker flags or deal with any other |
|
minutiae. |
|
|
|
If you have multiple dependencies, pass them as an array: |
|
|
|
```meson |
|
executable('manydeps', 'file.c', dependencies : [dep1, dep2, dep3, dep4]) |
|
``` |
|
|
|
If the dependency is optional, you can tell Meson not to error out if |
|
the dependency is not found and then do further configuration. |
|
|
|
```meson |
|
opt_dep = dependency('somedep', required : false) |
|
if opt_dep.found() |
|
# Do something. |
|
else |
|
# Do something else. |
|
endif |
|
``` |
|
|
|
You can pass the `opt_dep` variable to target construction functions |
|
whether the actual dependency was found or not. Meson will ignore |
|
non-found dependencies. |
|
|
|
Meson also allows to get variables that are defined in the |
|
`pkg-config` file. This can be done by using the |
|
`get_pkgconfig_variable` function. |
|
|
|
```meson |
|
zdep_prefix = zdep.get_pkgconfig_variable('prefix') |
|
``` |
|
|
|
These variables can also be redefined by passing the `define_variable` |
|
parameter, which might be useful in certain situations: |
|
|
|
```meson |
|
zdep_prefix = zdep.get_pkgconfig_variable('libdir', define_variable: ['prefix', '/tmp']) |
|
``` |
|
|
|
The dependency detector works with all libraries that provide a |
|
`pkg-config` file. Unfortunately several packages don't provide |
|
pkg-config files. Meson has autodetection support for some of these, |
|
and they are described later on this page. |
|
|
|
# Declaring your own |
|
|
|
You can declare your own dependency objects that can be used |
|
interchangeably with dependency objects obtained from the system. The |
|
syntax is straightforward: |
|
|
|
```meson |
|
my_inc = include_directories(...) |
|
my_lib = static_library(...) |
|
my_dep = declare_dependency(link_with : my_lib, |
|
include_directories : my_inc) |
|
``` |
|
|
|
This declares a dependency that adds the given include directories and |
|
static library to any target you use it in. |
|
|
|
# Building dependencies as subprojects |
|
|
|
Many platforms do not provide a system package manager. On these |
|
systems dependencies must be compiled from source. Meson's subprojects |
|
make it simple to use system dependencies when they are available and |
|
to build dependencies manually when they are not. |
|
|
|
To make this work, the dependency must have Meson build definitions |
|
and it must declare its own dependency like this: |
|
|
|
foo_dep = declare_dependency(...) |
|
|
|
Then any project that wants to use it can write out the following |
|
declaration in their main `meson.build` file. |
|
|
|
foo_dep = dependency('foo', fallback : ['foo', 'foo_dep']) |
|
|
|
What this declaration means is that first Meson tries to look up the |
|
dependency from the system (such as by using pkg-config). If it is not |
|
available, then it builds subproject named `foo` and from that |
|
extracts a variable `foo_dep`. That means that the return value of |
|
this function is either an external or an internal dependency |
|
object. Since they can be used interchangeably, the rest of the build |
|
definitions do not need to care which one it is. Meson will take care |
|
of all the work behind the scenes to make this work. |
|
|
|
# Dependencies with custom lookup functionality |
|
|
|
## Boost |
|
|
|
Boost is not a single dependency but rather a group of different |
|
libraries. To use Boost headers-only libraries, simply add Boost as a |
|
dependency. |
|
|
|
```meson |
|
boost_dep = dependency('boost') |
|
exe = executable('myprog', 'file.cc', dependencies : boost_dep) |
|
``` |
|
|
|
To link against boost with Meson, simply list which libraries you would like to |
|
use. |
|
|
|
```meson |
|
boost_dep = dependency('boost', modules : ['thread', 'utility']) |
|
exe = executable('myprog', 'file.cc', dependencies : boost_dep) |
|
``` |
|
|
|
You can call `dependency` multiple times with different modules and |
|
use those to link against your targets. |
|
|
|
If your boost headers or libraries are in non-standard locations you |
|
can set the BOOST_ROOT, BOOST_INCLUDEDIR, and/or BOOST_LIBRARYDIR |
|
environment variables. |
|
|
|
You can set the argument `threading` to `single` to use boost libraries that |
|
has been compiled for single-threaded use instead. |
|
|
|
## GTest and GMock |
|
|
|
GTest and GMock come as sources that must be compiled as part of your |
|
project. With Meson you don't have to care about the details, just |
|
pass `gtest` or `gmock` to `dependency` and it will do everything for |
|
you. If you want to use GMock, it is recommended to use GTest as well, |
|
as getting it to work standalone is tricky. |
|
|
|
## MPI |
|
|
|
MPI is supported for C, C++ and Fortran. Because dependencies are |
|
language-specific, you must specify the requested language using the |
|
`language` keyword argument, i.e., |
|
* `dependency('mpi', language='c')` for the C MPI headers and libraries |
|
* `dependency('mpi', language='cpp')` for the C++ MPI headers and libraries |
|
* `dependency('mpi', language='fortran')` for the Fortran MPI headers and libraries |
|
|
|
Meson prefers pkg-config for MPI, but if your MPI implementation does |
|
not provide them, it will search for the standard wrapper executables, |
|
`mpic`, `mpicxx`, `mpic++`, `mpifort`, `mpif90`, `mpif77`. If these |
|
are not in your path, they can be specified by setting the standard |
|
environment variables `MPICC`, `MPICXX`, `MPIFC`, `MPIF90`, or |
|
`MPIF77`, during configuration. |
|
|
|
## Qt5 |
|
|
|
Meson has native Qt5 support. Its usage is best demonstrated with an |
|
example. |
|
|
|
```meson |
|
qt5_mod = import('qt5') |
|
qt5widgets = dependency('qt5', modules : 'Widgets') |
|
|
|
processed = qt5_mod.preprocess( |
|
moc_headers : 'mainWindow.h', # Only headers that need moc should be put here |
|
moc_sources : 'helperFile.cpp', # must have #include"moc_helperFile.cpp" |
|
ui_files : 'mainWindow.ui', |
|
qresources : 'resources.qrc', |
|
) |
|
|
|
q5exe = executable('qt5test', |
|
sources : ['main.cpp', |
|
'mainWindow.cpp', |
|
processed], |
|
dependencies: qt5widgets) |
|
``` |
|
|
|
Here we have an UI file created with Qt Designer and one source and |
|
header file each that require preprocessing with the `moc` tool. We |
|
also define a resource file to be compiled with `rcc`. We just have to |
|
tell Meson which files are which and it will take care of invoking all |
|
the necessary tools in the correct order, which is done with the |
|
`preprocess` method of the `qt5` module. Its output is simply put in |
|
the list of sources for the target. The `modules` keyword of |
|
`dependency` works just like it does with Boost. It tells which |
|
subparts of Qt the program uses. |
|
|
|
## Dependencies using config tools |
|
|
|
CUPS, LLVM, PCAP, WxWidgets, libwmf, and GnuStep either do not provide |
|
pkg-config modules or additionally can be detected via a config tool |
|
(cups-config, llvm-config, etc). Meson has native support for these tools, and |
|
then can be found like other dependencies: |
|
|
|
```meson |
|
pcap_dep = dependency('pcap', version : '>=1.0') |
|
cups_dep = dependency('cups', version : '>=1.4') |
|
llvm_dep = dependency('llvm', version : '>=4.0') |
|
``` |
|
|
|
Some of these tools (like wmf and cups) provide both pkg-config and config |
|
tools support. You can force one or another via the method keyword: |
|
|
|
```meson |
|
wmf_dep = dependency('wmf', method : 'config-tool') |
|
``` |
|
|
|
## LLVM |
|
|
|
Meson has native support for LLVM going back to version LLVM version 3.5. |
|
It supports a few additional features compared to other config-tool based |
|
dependencies. |
|
|
|
As of 0.44.0 Meson supports the `static` keyword argument for LLVM. Before this |
|
LLVM >= 3.9 would always dynamically link, while older versions would |
|
statically link, due to a quirk in `llvm-config`. |
|
|
|
### Modules, a.k.a. Components |
|
|
|
Meson wraps LLVM's concept of components in it's own modules concept. |
|
When you need specific components you add them as modules as meson will do the |
|
right thing: |
|
|
|
```meson |
|
llvm_dep = dependency('llvm', version : '>= 4.0', modules : ['amdgpu']) |
|
``` |
|
|
|
As of 0.44.0 it can also take optional modules (these will affect the arguments |
|
generated for a static link): |
|
|
|
```meson |
|
llvm_dep = dependency( |
|
'llvm', version : '>= 4.0', modules : ['amdgpu'], optional_modules : ['inteljitevents'], |
|
) |
|
```
|
|
|