Submitted by: @romansimakov

roman@roman-home % ./isql firebird/gen/Debug/firebird/bin
Use CONNECT or CREATE DATABASE to specify a database
SQL> create database '/tmp/buffb.fdb';
SQL> ^D% roman@roman-home % roman@roman-home % ./gfix -buffers 1000000 /tmp/buffb.fdb firebird/gen/Debug/firebird/bin
I/O error during "read" operation for file "/tmp/buffb.fdb"
-Error while trying to read from file
-Bad address

Firebird 3.0 works correctly

Commits: 8491f42 9bb7211