First hitch I've noticed with 10.9: "gdb" seems to be missing. Gcc is still there. I've looked around to see if there's another optional download that I'm missing (like a Command Line Tools for Mavericks), but I don't see one.
Looks like Xcode is using lldb for debugging, and I can use lldb on the command line. I guess lldb is now the standard 1st-party debugger? Guess I will be figuring out how to install gdb manually..
You are correct, gdb is phased out in favor of lldb. It's just the end of a very long transitional period, similar to the clang vs. gcc situation. Introduce the successor, support both for several releases, then finally drop the legacy component. You can still install gdb yourself of course.
Protip: While old Apple builds of gcc will still work on Mavericks, newer FSF gdb won't load any shared libraries. To fix it, just change DYLD_VERSION_MAX in gdb/solib-darwin.c from 12 to 14.
xistence$ gcc --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin13.0.0
Thread model: posix
Command line tools for Mavericks are a separate download, it is no longer available in the Xcode downloads section. Start Xcode, click Xcode in the top left next the Apple in the menu bar, select "Open Developer Tool", click "More Developer Tools" to go directly to the site, log in with your apple developer ID and download the command line tools.
The command line tools also make sure to install a whole range of standard headers that are not included with Xcode so that you can build curses based apps and all that fun stuff!
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With gcc missing, so is libstdc++ for linking/compiling against.
Looks like Xcode is using lldb for debugging, and I can use lldb on the command line. I guess lldb is now the standard 1st-party debugger? Guess I will be figuring out how to install gdb manually..