Gala 8.0.3 fails to build with Mutter 45.5

[pimvullers]

What Happened?

Building gala on Gentoo with Mutter 45.5 failed with following error:

libmutter-13.vapi:1120.10-1120.14: error: The type name `pid_t' could not be found
 1120 | 		public pid_t get_pid ();
      | 		       ^~~~~            
../gala-8.0.3/lib/App.vala:161.23-161.28: error: The type name `pid_t' could not be found
  161 |     public GLib.SList<pid_t?> get_pids () {
      |                       ^~~~~~               
../gala-8.0.3/lib/App.vala:162.38-162.43: error: The type name `pid_t' could not be found
  162 |         var results = new GLib.SList<pid_t?> ();
      |                                      ^~~~~~     
Compilation failed: 3 error(s), 0 warning(s)

Steps to Reproduce

Use Mutter 45.5, build gala

Expected Behavior

Build passes

OS Version

Other Linux

Session Type

Classic Session (X11, This is the default)

Software Version

Latest release (I have run all updates)

Log Output

No response

Hardware Info

No response

[pimvullers]

Comparing to Gala-8.0.2 the previous type was int instead of pid_t. Reverting this part with below command fixes build:

sed -i -e "s#pid_t#int#" vapi/libmutter.vapi lib/App.vala src/WindowTracker.vala

[tintou]

I'm guessing it is because of your Vala version

[tintou]

You need 0.56.17 to have the pid_t type

[pimvullers]

Thanks, Gentoo is currently at 0.56.16 as stable. 0.56.17 is only available in unstable.
Might be good to have meson actually ensure proper vala version.