"Qt SDK for Mac" is 32-bit, only, and does not have 64-bit support, leading to compilation failures under Mac OS X 10.6 Snow Leopard.

On Mac OS X 10.6 Snow Leopard, the compiler generates binaries for the x86_64 architecture, by default. Because the "Qt SDK for Mac" distribution contains only the i386 and ppc architectures, this causes builds to fail on Mac OS X 10.6 Snow Leopard. While applications that rely on the Qt SDK, only, have the option of adding the "-arch i386" flag to force compilation for that architecture, many programs have other third-party library dependencies and, since x86_64 is the default architecture on Mac OS X 10.6 Snow Leopard, it is more than likely that those libraries will have been built for x86_64, only. Qt should follow Apple's lead by supporting exactly two versions of Mac OS X (the current version and the version before it) and by dropping support for the Power PC. The "Qt SDK for Mac" package should contain Cocoa-based universal Mach-O binaries for the i386 and x86_64 architectures.