It seems GNU GCC 4.2 is not supported from Xcode 4.2.

■ Xcode 4.1 以前 / Xcode 4.1 and Earlier

GCC 4.2 LLVM GCC 4.2 LLVM Compiler 2.0

■ Xcode 4.2

LLVM GCC 4.2 Apple LLVM Compiler 3.0

・Reference: Xcode 4.2で変わったビルド設定（アーキテクチャとコンパイラ）と問題点などについて - Awaresoft

I got stuck on various issues without knowing that GCC 4.2 was no longer available.

Please be careful, everyone.

That’s all from the Gemba regarding Xcode compiler changes.