PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> With default compiler /usr/bin/gcc-4.2 (powerpc-apple-darwin9-gcc-4.2.1
> (GCC) 4.2.1 (Apple Inc. build 5577)) the error is:
> pg_collation.c:55: error: conflicting types for ‘CollationCreate’
PG 12 is EOL, so we won't be doing anything about this. However,
it's evident from your messages that the problem is something
about "bool" (probably our typedef as "char") versus "_Bool"
(C99 <stdbool.h>). If you need a fix for PG 12, you might get
somewhere by trawling later branches' commit history for fixes
related to that.
regards, tom lane