New features
(C) Preprocessor flag handling
Meson previously stored CPPFLAGS
and per-language compilation flags
separately. (That latter would come from CFLAGS
, CXXFLAGS
, etc.,
along with <lang>_args
options whether specified no the command-line
interface (-D..
), meson.build
(default_options
), or cross file
([properties]
).) This was mostly unobservable, except for certain
preprocessor-only checks like check_header
would only use the
preprocessor flags, leading to confusion if some -isystem
was in
CFLAGS
but not CPPFLAGS
. Now, they are lumped together, and
CPPFLAGS
, for the languages which are deemed to care to about, is
just another source of compilation flags along with the others already
listed.
Sanity checking compilers with user flags
Sanity checks previously only used user-specified flags for cross compilers, but now do in all cases.
All compilers Meson might decide to use for the build are "sanity checked" before other tests are run. This usually involves building simple executable and trying to run it. Previously user flags (compilation and/or linking flags) were used for sanity checking cross compilers, but not native compilers. This is because such flags might be essential for a cross binary to succeed, but usually aren't for a native compiler.
In recent releases, there has been an effort to minimize the special-casing of cross or native builds so as to make building more predictable in less-tested cases. Since this the user flags are necessary for cross, but not harmful for native, it makes more sense to use them in all sanity checks than use them in no sanity checks, so this is what we now do.
New sourceset
module
A new module, sourceset
, was added to help building many binaries
from the same source files. Source sets associate source files and
dependencies to keys in a configuration_data
object or a dictionary;
they then take multiple configuration_data
objects or dictionaries,
and compute the set of source files and dependencies for each of those
configurations.
n_debug=if-release and buildtype=plain means no asserts
Previously if this combination was used then assertions were enabled, which is fairly surprising behavior.
target_type
in build_targets
accepts the value 'shared_module'
The target_type
keyword argument in build_target()
now accepts the
value 'shared_module'
.
The statement
build_target(..., target_type: 'shared_module')
is equivalent to this:
shared_module(...)
New modules kwarg for python.find_installation
This mirrors the modules argument that some kinds of dependencies (such as qt, llvm, and cmake based dependencies) take, allowing you to check that a particular module is available when getting a python version.
py = import('python').find_installation('python3', modules : ['numpy'])
Support for the Intel Compiler on Windows (ICL)
Support has been added for ICL.EXE and ifort on windows. The support
should be on part with ICC support on Linux/MacOS. The ICL C/C++
compiler behaves like Microsoft's CL.EXE rather than GCC/Clang like
ICC does, and has a different id, intel-cl
to differentiate it.
cc = meson.get_compiler('c')
if cc.get_id == 'intel-cl'
add_project_argument('/Qfoobar:yes', language : 'c')
endif
Added basic support for the Xtensa CPU toolchain
You can now use xt-xcc
, xt-xc++
, xt-nm
, etc... on your cross
compilation file and Meson won't complain about an unknown toolchain.
Dependency objects now have a get_variable method
This is a generic replacement for type specific variable getters such as
ConfigToolDependency.get_configtool_variable
and
PkgConfigDependency.get_pkgconfig_variable
, and is the only way to query
such variables from cmake dependencies.
This method allows you to get variables without knowing the kind of dependency you have.
dep = dependency('could_be_cmake_or_pkgconfig')
# cmake returns 'YES', pkg-config returns 'ON'
if ['YES', 'ON'].contains(dep.get_variable(pkgconfig : 'var-name', cmake : 'COP_VAR_NAME', default_value : 'NO'))
error('Cannot build your project when dep is built with var-name support')
endif
CMake prefix path overrides
When using pkg-config as a dependency resolver we can pass
-Dpkg_config_path=$somepath
to extend or overwrite where pkg-config
will search for dependencies. Now cmake can do the same, as long as
the dependency uses a ${Name}Config.cmake file (not a
Find{$Name}.cmake file), by passing
-Dcmake_prefix_path=list,of,paths
. It is important that point this
at the prefix that the dependency is installed into, not the cmake
path.
If you have installed something to /tmp/dep
, which has a layout like:
/tmp/dep/lib/cmake
/tmp/dep/bin
then invoke Meson as meson setup builddir/ -Dcmake_prefix_path=/tmp/dep
Tests that should fail but did not are now errors
You can tag a test as needing to fail like this:
test('shouldfail', exe, should_fail: true)
If the test passes the problem is reported in the error logs but due to a bug it was not reported in the test runner's exit code. Starting from this release the unexpected passes are properly reported in the test runner's exit code. This means that test runs that were passing in earlier versions of Meson will report failures with the current version. This is a good thing, though, since it reveals an error in your test suite that has, until now, gone unnoticed.
New target keyword argument: link_language
There may be situations for which the user wishes to manually specify the linking language. For example, a C++ target may link C, Fortran, etc. and perhaps the automatic detection in Meson does not pick the desired compiler. The user can manually choose the linker by language per-target like this example of a target where one wishes to link with the Fortran compiler:
executable(..., link_language : 'fortran')
A specific case this option fixes is where for example the main
program is Fortran that calls C and/or C++ code. The automatic
language detection of Meson prioritizes C/C++, and so an compile-time
error results like undefined reference to main
, because the linker
is C or C++ instead of Fortran, which is fixed by this per-target
override.
New module to parse kconfig output files
The new module unstable-kconfig
adds the ability to parse and use
kconfig output files from meson.build
.
Add new meson subprojects foreach
command
meson subprojects
has learned a new foreach
command which accepts
a command with arguments and executes it in each subproject directory.
For example this can be useful to check the status of subprojects
(e.g. with git status
or git diff
) before performing other actions
on them.
Added c17 and c18 as c_std values for recent GCC and Clang Versions
For gcc version 8.0 and later, the values c17, c18, gnu17, and gnu18 were added to the accepted values for built-in compiler option c_std.
For Clang version 10.0 and later on Apple OSX (Darwin), and for version 7.0 and later on other platforms, the values c17 and gnu17 were added as c_std values.
gpgme dependency now supports gpgme-config
Previously, we could only detect GPGME with custom invocations of
gpgme-config
or when the GPGME version was recent enough (>=1.13.0)
to install pkg-config files. Now we added support to Meson allowing us
to use dependency('gpgme')
and fall back on gpgme-config
parsing.
Can link against custom targets
The output of custom_target
and custom_target[i]
can be used in
link_with
and link_whole
keyword arguments. This is useful for
integrating custom code generator steps, but note that there are many
limitations:
-
Meson cannot know about link dependencies of the custom target. If the target requires further link libraries, you need to add them manually
-
The user is responsible for ensuring that the code produced by different toolchains are compatible.
-
custom_target
may only be used when it has a single output file. Usecustom_target[i]
when dealing with multiple output files. -
The output file must have the correct file name extension.
Removed the deprecated --target-files
API
The --target-files
introspection API is now no longer available. The same
information can be queried with the --targets
API introduced in 0.50.0.
Generators have a new depends
keyword argument
Generators can now specify extra dependencies with the depends
keyword argument. It matches the behaviour of the same argument in
other functions and specifies that the given targets must be built
before the generator can be run. This is used in cases such as this
one where you need to tell a generator to indirectly invoke a
different program.
exe = executable(...)
cg = generator(program_runner,
output: ['@BASENAME@.c'],
arguments: ['--use-tool=' + exe.full_path(), '@INPUT@', '@OUTPUT@'],
depends: exe)
Specifying options per mer machine
Previously, no cross builds were controllable from the command line.
Machine-specific options like the pkg-config path and compiler options
only affected native targets, that is to say all targets in native
builds, and native: true
targets in cross builds. Now, prefix the
option with build.
to affect build machine targets, and leave it
unprefixed to affect host machine targets.
For those trying to ensure native and cross builds to the same platform produced the same result, the old way was frustrating because very different invocations were needed to affect the same targets, if it was possible at all. Now, the same command line arguments affect the same targets everywhere --- Meson is closer to ignoring whether the "overall" build is native or cross, and just caring about whether individual targets are for the build or host machines.
subproject.get_variable() now accepts a fallback
argument
Similar to get_variable
, a fallback argument can now be passed to
subproject.get_variable()
, it will be returned if the requested
variable name did not exist.
var = subproject.get_variable('does-not-exist', 'fallback-value')
Add keyword static
to find_library
find_library
has learned the static
keyword. They keyword must be
a boolean, where true
only searches for static libraries and false
only searches for dynamic/shared. Leaving the keyword unset will keep
the old behavior of first searching for dynamic and then falling back
to static.
Fortran include
statements recursively parsed
While non-standard and generally not recommended, some legacy Fortran
programs use include
directives to inject code inline. Since v0.51,
Meson can handle Fortran include
directives recursively.
DO NOT list include
files as sources for a target, as in general
their syntax is not correct as a standalone target. In general
include
files are meant to be injected inline as if they were copy
and pasted into the source file.
include
was never standard and was superseded by Fortran 90 module
.
The include
file is only recognized by Meson if it has a Fortran
file suffix, such as .f
.F
.f90
.F90
or similar. This is to
avoid deeply nested scanning of large external legacy C libraries that
only interface to Fortran by include biglib.h
or similar.
CMake subprojects
Meson can now directly consume CMake based subprojects with the CMake module.
Using CMake subprojects is similar to using the "normal" Meson
subprojects. They also have to be located in the subprojects
directory.
Example:
add_library(cm_lib SHARED ${SOURCES})
cmake = import('cmake')
# Configure the CMake project
sub_proj = cmake.subproject('libsimple_cmake')
# Fetch the dependency object
cm_lib = sub_proj.dependency('cm_lib')
executable('exe1', ['sources'], dependencies: [cm_lib])
It should be noted that not all projects are guaranteed to work. The
safest approach would still be to create a meson.build
for the
subprojects in question.
Multiple cross files can be specified
--cross-file
can be passed multiple times, with the configuration files overlaying the same way as --native-file
.
The results of the search are