PostgreSQL stops when adding a breakpoint in CLion

I tried debugging PostgreSQL to better understand how it works. It worked
fine a day ago, but for some reason I have issues with debugging now:

- If I put a breakpoint before I start the process then everything works
fine
- But if I put/remove a breakpoint after it's fully initialized - the
process just stops

And when reading the next command postgres.c, I see that input_message is
empty. I assume CLion sends a signal which awakens PostgreSQL, but there's
no data on the input? But should PostgreSQL quit in such a situation?

The way I build and start:
make clean
./configure --enable-cassert --enable-debug CFLAGS="-ggdb -O0 -g3
-fno-omit-frame-pointer"
make
make install
/usr/local/pgsql/bin/initdb -D /Users/stas/projects/postgres/data

Starting command:
/usr/local/pgsql/bin/postgres --single -D
/Users/stas/projects/postgres/data postgres