If you prefer to use an IDE (with GCC and MINGW or MINGW64) there is http://www.codeblocks.org/.
[firebird-support] Re: C++/C compiler for Firebird 3 UDF on Windows - free version?
Mauricio Gomes mgpen...@gmail.com [firebird-support] Fri, 16 Mar 2018 07:03:08 -0700