From:
http://gcc.gnu.org/codingconventions.html
Use... ...instead of Rationale
"built-in" as an adjective ("built-in function") or "built in"
"builtin"
"builtin" isn't a word
But the manual uses it:
5.48 Object Size Checking Builtins
--
Summary: "Builtins" is used when the code Conventions say don't
use it
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Keywords: documentation
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: pinskia at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38376