MACOSX_DEPLOYMENT_TARGET

I have read in a number of places that I should be using

gcc -mmacosx-version-min=10.4

rather than the

MACOSX_DEPLOYMENT_TARGET=10.4

environment variable because the latter has now been deprecated.

NO! Any attempt to compile Firebird on MacOS 10.5 and run it on MacOS 10.4 will create bus errors. You must set the MACOSX_DEPLOYMENT_TARGET variable!

(The Firebird build environment now uses both - just to make 100% certain)