meson/docs/markdown/Release-notes-for-0.42.0.md

---
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' )
```