gdb 已被 lldb 取代，不再受支持。 gcc 和 llvm-gcc 也不见了，取而代之的是 clang 。

I went to use GDB in OS X v10.9 (Mavericks), and it's not there. Where has it gone?

# /usr/lib/gdb
-bash: /usr/bin/gdb: No such file or directory
# gdb
-bash: gdb: command not found

I also launched Xcode 5.0.1:

Preferences > Downloads

..and there's no longer command line tools available — ffs!

gdb has been replaced by lldb, and is no longer supported. gcc and llvm-gcc are also gone, replaced by clang.