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+---
+title: Release 0.56.0
+short-description: Release notes for 0.56.0
+...
+
+# New features
+
+## Python 3.5 support will be dropped in the next release
+
+The final [Python 3.5 release was 3.5.10 in
+September](https://www.python.org/dev/peps/pep-0478/#id4). This
+release series is now End-of-Life (EOL). The only LTS distribution
+that still only ships Python 3.5 is Ubuntu 16.04, which will be [EOL
+in April 2021](https://ubuntu.com/about/release-cycle).
+
+Python 3.6 has numerous features that we find useful such as improved
+support for the `typing` module, f-string support, and better
+integration with the `pathlib` module.
+
+As a result, we will begin requiring Python 3.6 or newer in Meson
+0.57, which is the next release. Starting with Meson 0.56, we now
+print a `NOTICE:` when a `meson` command is run on Python 3.5 to
+inform users about this. This notice has also been backported into the
+0.55.2 stable release.
+
+## `meson test` can now filter tests by subproject
+
+You could always specify a list of tests to run by passing the names
+as arguments to `meson test`. If there were multiple tests with that
+name (in the same project or different subprojects), all of them would
+be run. Now you can:
+
+1. Run all tests with the specified name from a specific subproject: `meson test subprojname:testname`
+1. Run all tests defined in a specific subproject: `meson test subprojectname:`
+
+As before, these can all be specified multiple times and mixed:
+
+```sh
+# Run:
+# * All tests called 'name1' or 'name2' and
+# * All tests called 'name3' in subproject 'bar' and
+# * All tests in subproject 'foo'
+$ meson test name1 name2 bar:name3 foo:
+```
+
+## Native (build machine) compilers not always required by `project()`
+
+When cross-compiling, native (build machine) compilers for the
+languages specified in `project()` are not required, if no targets use
+them.
+
+## New `extra_files` key in target introspection
+
+The target introspection (`meson introspect --targets`,
+`intro-targets.json`) now has the new `extra_files` key which lists
+all files specified via the `extra_files` kwarg of a build target (see
+`executable()`, etc.)
+
+
+## Preliminary AIX support
+
+AIX is now supported when compiling with gcc. A number of features are
+not supported yet. For example, only gcc is supported (not xlC).
+Archives with both 32-bit and 64-bit dynamic libraries are not
+generated automatically. The rpath includes both the build and install
+rpath, no attempt is made to change the rpath at install time. Most
+advanced features (eg. link\_whole) are not supported yet.
+
+## Wraps from subprojects are automatically promoted
+
+It is not required to promote wrap files for subprojects into the main
+project any more. When configuring a subproject, Meson will look for
+any wrap file or directory in the subproject's `subprojects/`
+directory and add them into the global list of available subprojects,
+to be used by any future `subproject()` call or `dependency()`
+fallback. If a subproject with the same name already exists, the new
+wrap file or directory is ignored. That means that the main project
+can always override any subproject's wrap files by providing their
+own, it also means the ordering in which subprojects are configured
+matters, if 2 subprojects provide foo.wrap only the one from the first
+subproject to be configured will be used.
+
+This new behavior can be disabled by passing `--wrap-mode=nopromote`.
+
+## `meson.build_root()` and `meson.source_root()` are deprecated
+
+Those function are common source of issue when used in a subproject
+because they point to the parent project root which is rarely what is
+expected and is a violation of subproject isolation.
+
+`meson.current_source_dir()` and `meson.current_build_dir()` should be
+used instead and have been available in all Meson versions. New
+functions `meson.project_source_root()` and
+`meson.project_build_root()` have been added in Meson 0.56.0 to get
+the root of the current (sub)project.
+
+## `dep.as_link_whole()`
+
+Dependencies created with `declare_dependency()` now has new method
+`as_link_whole()`. It returns a copy of the dependency object with all
+link_with arguments changed to link_whole. This is useful for example
+for fallback dependency from a subproject built with
+`default_library=static`.
+
+```meson
+somelib = static_library('somelib', ...)
+dep = declare_dependency(..., link_with: somelib)
+library('someotherlib', ..., dependencies: dep.as_link_whole())
+```
+
+## Add support for all Windows subsystem types
+
+It is now possible to build things like Windows kernel drivers with
+the new `win_subsystem` keyword argument. This replaces the old
+`gui_app` keyword argument, which is now deprecated. You should update
+your project to use the new style like this:
+
+```meson
+# Old way
+executable(..., gui_app: 'true')
+# New way
+executable(..., win_subsystem: 'windows')
+```
+
+The argument supports versioning [as described on MSDN
+documentation](https://docs.microsoft.com/en-us/cpp/build/reference/subsystem-specify-subsystem).
+Thus to build a Windows kernel driver with a specific version you'd
+write something like this:
+
+```meson
+executable(..., win_subsystem: 'native,6.02')
+```
+
+## Added NVidia HPC SDK compilers
+
+Added support for `nvidia_hpc` NVidia HPC SDK compilers, which are currently in public beta testing.
+
+## Project and built-in options can be set in native or cross files
+
+A new set of sections has been added to the cross and native files,
+`[project options]` and `[<subproject_name>:project options]`, where
+`subproject_name` is the name of a subproject. Any options that are
+allowed in the project can be set from this section. They have the
+lowest precedent, and will be overwritten by command line arguments.
+
+
+```meson
+option('foo', type : 'string', value : 'foo')
+```
+
+```ini
+[project options]
+foo = 'other val'
+```
+
+```console
+meson builddir/ --native-file my.ini
+```
+
+Will result in the option foo having the value `other val`,
+
+```console
+meson builddir/ --native-file my.ini -Dfoo='different val'
+```
+
+Will result in the option foo having the value `different val`,
+
+
+Subproject options are assigned like this:
+
+```ini
+[zlib:project options]
+foo = 'some val'
+```
+
+Additionally Meson level options can be set in the same way, using the
+`[built-in options]` section.
+
+```ini
+[built-in options]
+c_std = 'c99'
+```
+
+These options can also be set on a per-subproject basis, although only
+`default_library` and `werror` can currently be set:
+```ini
+[zlib:built-in options]
+default_library = 'static'
+```
+
+## `unstable-keyval` is now stable `keyval`
+
+The `unstable-keyval` has been renamed to `keyval` and now promises stability
+guarantees.
+
+Meson will print a warning when you load an `unstable-` module that has been
+stabilised (so `unstable-keyval` is still accepted for example).
+
+## CMake subproject cross compilation support
+
+Meson now supports cross compilation for CMake subprojects. Meson will
+try to automatically guess most of the required CMake toolchain
+variables from existing entries in the cross and native files. These
+variables will be stored in an automatically generate CMake toolchain
+file in the build directory. The remaining variables that can't be
+guessed can be added by the user in the new `[cmake]` cross/native
+file section.
+
+## Machine file keys are stored case sensitive
+
+Previous the keys were always lowered, which worked fine for the
+values that were allowed in the machine files. With the addition of
+per-project options we need to make these sensitive to case, as the
+options in meson_options.txt are sensitive to case already.
+
+## Consistency between `declare_dependency()` and `pkgconfig.generate()` variables
+
+The `variables` keyword argument in `declare_dependency()` used to
+only support dictionary and `pkgconfig.generate()` only list of
+strings. They now both support dictionary and list of strings in the
+format `'name=value'`. This makes easier to share a common set of
+variables for both:
+
+```meson
+vars = {'foo': 'bar'}
+dep = declare_dependency(..., variables: vars)
+pkg.generate(..., variables: vars)
+```
+
+## Qt5 compile_translations now supports qresource preprocessing
+
+When using qtmod.preprocess() in combination with
+qtmod.compile_translations() to embed translations using rcc, it is no
+longer required to do this:
+
+```meson
+ts_files = ['list', 'of', 'files']
+qtmod.compile_translations(ts_files)
+# lang.qrc also contains the duplicated list of files
+lang_cpp = qtmod.preprocess(qresources: 'lang.qrc')
+```
+
+Instead, use:
+```meson
+lang_cpp = qtmod.compile_translations(qresource: 'lang.qrc')
+```
+
+which will automatically detect and generate the needed
+compile_translations targets.
+
+## Controlling subproject dependencies with `dependency(allow_fallback: ...)`
+
+As an alternative to the `fallback` keyword argument to `dependency`,
+you may use `allow_fallback`, which accepts a boolean value. If `true`
+and the dependency is not found on the system, Meson will fallback to
+a subproject that provides this dependency, even if the dependency is
+optional. If `false`, Meson will not fallback even if a subproject
+provides this dependency.
+
+## Custom standard library
+
+- It is not limited to cross builds any more, `<lang>_stdlib` property can be
+ set in native files.
+- The variable name parameter is no longer required as long as the subproject
+ calls `meson.override_dependency('c_stdlib', mylibc_dep)`.
+
+## Improvements for the builtin curses dependency
+
+This method has been extended to use config-tools, and a fallback to
+find_library for lookup as well as pkg-config.
+
+## HDF5 dependency improvements
+
+HDF5 has been improved so that the internal representations have been
+split. This allows selecting pkg-config and config-tool dependencies
+separately. Both work as proper dependencies of their type, so
+`get_variable` and similar now work correctly.
+
+It has also been fixed to use the selected compiler for the build instead of
+the default compiler.
+
+## External projects
+
+A new experimental module `unstable_external_project` has been added
+to build code using other build systems than Meson. Currently only
+supporting projects with a configure script that generates Makefiles.
+
+```meson
+project('My Autotools Project', 'c',
+ meson_version : '>=0.56.0',
+)
+
+mod = import('unstable_external_project')
+
+p = mod.add_project('configure',
+ configure_options : ['--prefix=@PREFIX@',
+ '--libdir=@LIBDIR@',
+ '--incdir=@INCLUDEDIR@',
+ '--enable-foo',
+ ],
+)
+
+mylib_dep = p.dependency('mylib')
+```
+
+
+## Per subproject `warning_level` option
+
+`warning_level` can now be defined per subproject, in the same way as
+`default_library` and `werror`.
+
+## `meson subprojects` command
+
+A new `--types` argument has been added to all subcommands to run the
+command only on wraps with the specified types. For example this
+command will only print `Hello` for each git subproject: `meson
+subprojects foreach --types git echo "Hello"`. Multiple types can be
+set as comma separated list e.g. `--types git,file`.
+
+Subprojects with no wrap file are now taken into account as well. This
+happens for example for subprojects configured as git submodule, or
+downloaded manually by the user and placed into the `subprojects/`
+directory.
+
+The `checkout` subcommand now always stash any pending changes before
+switching branch. Note that `update` subcommand was already stashing
+changes before updating the branch.
+
+If the command fails on any subproject the execution continues with
+other subprojects, but at the end an error code is now returned.
+
+The `update` subcommand has been reworked:
+- In the case the URL of `origin` is different as the `url` set in wrap file,
+ the subproject will not be updated unless `--reset` is specified (see below).
+- In the case a subproject directory exists and is not a git repository but has
+ a `[wrap-git]`, Meson used to run git commands that would wrongly apply to the
+ main project. It now skip the subproject unless `--reset` is specified (see below).
+- The `--rebase` behaviour is now the default for consistency: it was
+ already rebasing when current branch and revision are the same, it is
+ less confusing to rebase when they are different too.
+- Add `--reset` mode that checkout the new branch and hard reset that
+ branch to remote commit. This new mode guarantees that every
+ subproject are exactly at the wrap's revision. In addition the URL of `origin`
+ is updated in case it changed in the wrap file. If the subproject directory is
+ not a git repository but has a `[wrap-git]` the directory is deleted and the
+ new repository is cloned.
+- Local changes are always stashed first to avoid any data loss. In the
+ worst case scenario the user can always check reflog and stash list to
+ rollback.
+
+## Added CompCert C compiler
+
+Added experimental support for the [CompCert formally-verified C
+compiler](https://github.com/AbsInt/CompCert). The current state of
+the implementation is good enough to build the [picolibc
+project](https://github.com/picolibc/picolibc) with CompCert, but
+might still need additional adjustments for other projects.
+
+## Dependencies listed in test and benchmark introspection
+
+The introspection data for tests and benchmarks now includes the
+target ids for executables and built files that are needed by the
+test. IDEs can use this feature to update the build more quickly
+before running a test.
+
+## `include_type` support for the CMake subproject object dependency method
+
+The `dependency()` method of the CMake subproject object now also
+supports the `include_type` kwarg which is similar to the sane kwarg
+in the `dependency()` function.
+
+## Deprecate Dependency.get_pkgconfig_variable and Dependency.get_configtool_variable
+
+These have been replaced with the more versatile `get_variable()` method
+already, and shouldn't be used anymore.