[fpc-pascal] fpc procedure modifier []

[Mattias Gaertner]

Hi,

Where can I find some information about the [] procedure modifier of
FPC?
For example:

procedure fpc_check_object(_vmt : pointer);
[public,alias:'FPC_CHECK_OBJECT'];  compilerproc;

What $modes support this?
The reason I ask is I'm trying to distinguish them from Delphi
Attributes in pparser.

Btw, 'compilerproc' is not listed here:
https://www.freepascal.org/docs-html/ref/refse97.html#x187-20900014.10

Mattias