Unknown type name bool

I am trying to build Postgres in an IDE (CLion on Ubuntu), and I'm getting
the following error message:

In file included from /workspace/src/postgres/src/include/c.h:61:0,
from /workspace/src/postgres/src/include/postgres.h:46,
from /workspace/src/postgres/contrib/bloom/blcost.c:13:
/workspace/src/postgres/src/include/common/string.h:13:8: error: unknown
type name ‘bool’
extern bool pg_str_endswith(const char *str, const char *end);

CLion created a CMakeLists.txt file with the following at the top:

cmake_minimum_required(VERSION 3.14)
project(postgres)
set(CMAKE_CXX_STANDARD 14)

And my compiler version is: gcc version 7.4.0 (Ubuntu
7.4.0-1ubuntu1~18.04.1)

Any thoughts? (disclaimer: I have much more experience with Java than C)

Thanks,

Igal