New features (in development)

New custom dependency for atomic

dependency('atomic')

checks for the availability of the atomic operation library. First, it looks for the atomic library. If that is not found, then it will try to use what is provided by the libc.

--cap-lints allow used for Cargo subprojects

Similar to Cargo itself, all downloaded Cargo subprojects automatically add the --cap-lints allow compiler argument, thus hiding any warnings from the compiler.

Related to this, warning_level=0 now translates into --cap-lints allow for Rust targets instead of -A warnings.

Cargo features are resolved globally

When configuring a Cargo dependency, Meson will now resolve its complete dependency tree and feature set before generating the subproject AST. This solves many cases of Cargo subprojects being configured with missing features that the main project had to enable by hand using e.g. default_options: ['foo-rs:feature-default=true'].

Note that there could still be issues in the case there are multiple Cargo entry points. That happens if the main Meson project makes multiple dependency() calls for different Cargo crates that have common dependencies.

Breaks: This change removes per feature Meson options that were previously possible to set as shown above or from command line -Dfoo-rs:feature-foo=true.

Meson can run "clippy" on Rust projects

Meson now defines a clippy target if the project uses the Rust programming language. The target runs clippy on all Rust sources, using the clippy-driver program from the same Rust toolchain as the rustc compiler.

Using clippy-driver as the Rust compiler will now emit a warning, as it is not meant to be a general-purpose compiler front-end.

Devenv support in external project module

The external project module now setups PATH and LD_LIBRARY_PATH to be able to run programs.

@BINDIR@ is now substitued in arguments and '--bindir=@PREFIX@/@BINDIR@' default argument have been added.

Fixed sizeof and find_library methods for Fortran compilers

The implementation of the .sizeof() method has been fixed for Fortran compilers (it was previously broken since it would try to compile a C code snippet). Note that this functionality requires Fortran 2008 support.

Incidentally this also fixes the .find_library() method for Fortran compilers when the prefer_static built-in option is set to true.

format command now accept stdin argument

You can now use - argument for meson format to read input from stdin instead of reading it from a file.

"machine" entry in target introspection data

The JSON data returned by meson introspect --targets now has a machine entry in each target_sources block. The new entry can be one of build or host for compiler-built targets, or absent for custom_target targets.

Add new language Linear Asm

TI C6000 compiler supports a dialect of TI asm, so we add a new language for it.

Control the number of child processes with an environment variable

Previously, meson test checked the MESON_TESTTHREADS variable to control the amount of parallel jobs to run; this was useful when meson test is invoked through ninja test for example. With this version, a new variable MESON_NUM_PROCESSES is supported with a broader scope: in addition to meson test, it is also used by the external_project module and by Ninja targets that invoke clang-tidy, clang-format and clippy.

Support for Rust 2024

Meson can now request the compiler to use the 2024 edition of Rust. Use rust_std=2024 to activate it. Rust 2024 requires the 1.85.0 version (or newer) of the compiler.

Test targets no longer built by default

meson test and the ninja all rule have been reworked to no longer force unnecessary rebuilds.

meson test was invoking ninja all due to a bug if the chosen set of tests had no build dependencies. The behavior is now the same as when tests do have build dependencies, i.e. to only build the actual set of targets that are used by the test. This change could cause failures when upgrading to Meson 1.7.0, if the dependencies are not specified correctly in meson.build. Using ninja test has always been guaranteed to "do the right thing" and rebuild all as well; this continues to work.

ninja all does not rebuild all tests anymore; it should be noted that this change means test programs are no longer guaranteed to have been built, depending on whether those test programs were also defined to build by default / marked as installable. This avoids building test-only binaries as part of installing the project (ninja && ninja install), which is unnecessary and has no use case.

Some users might have been relying on the "all" target building test dependencies in combination with meson test --no-rebuild in order to skip calling out to ninja when running tests. This might break with this change because, when given --no-rebuild, Meson provides no guarantee that test dependencies are present and up to date. The recommended workflow is to use either ninja test or ninja && meson test but, if you wish to build test programs and dependencies in a separate stage, you can use for example ninja all meson-test-prereq meson-benchmark-prereq before meson test --no-rebuild. These prereq targets have been available since meson 0.63.0.

Install vcs_tag() output

vcs_tag() now has install, install_dir, install_tag and install_mode keyword arguments to install the generated file.