---
title: Release 0.42
short-description: Release notes for 0.42 (preliminary)
...

**Preliminary, 0.42.0 has not been released yet.**

# New features

## Distribution tarballs from Mercurial repositories

Creating distribution tarballs can now be made out of projects based on
Mercurial. As before, this remains possible only with the Ninja backend.

## Keyword argument verification

Meson will now check the keyword arguments used when calling any function
and print a warning if any of the keyword arguments is not known. In the
future this will become a hard error.

## Add support for Genie to Vala compiler

The Vala compiler has an alternative syntax, Genie, that uses the `.gs`
file extension. Meson now recognises and uses Genie files.

## Pkgconfig support for additional cflags

The Pkgconfig module object can add arbitrary extra cflags to the Cflags
value in the .pc file, using the "extra_cflags" keyword:
```meson
pkg.generate(libraries : libs,
             subdirs : h,
             version : '1.0',
             name : 'libsimple',
             filebase : 'simple',
             description : 'A simple demo library.',
             extra_cflags : '-Dfoo' )
```

## Base options accessible via get_option()

Base options are now accessible via the get_option() function.
```meson
uses_lto = get_option('b_lto')
```

## Allow crate type configuration for Rust compiler

Rust targets now take an optional `rust_crate_type` keyword, allowing
you to set the crate type of the resulting artifact. Valid crate types
are `dylib` or `cdylib` for shared libraries, and `rlib` or
`staticlib` for static libraries. For more, see
Rust's [linkage reference][rust-linkage].

[rust-linkage]: https://doc.rust-lang.org/reference/linkage.html

## Simultaneous use of Address- and Undefined Behavior Sanitizers

Both the address- and undefined behavior sanitizers can now be used
simultaneously by passing `-Db_sanitize=address,undefined` to Meson.
