I'm using (Apple) LLVM 4.1 within Xcode 4.5 (but I saw the same thing in an earlier beta). I have it targeting C++11 and am using libc++ (the new, C++11 enabled, LLVM version of the std library).
In a debug build, if I try to step over code that calls into a std library function (e.g. a std::vector constructor) the debugger stops in the std lib implementation and if I try to step out it steps even deeper! It can take several (sometimes 10 or more) step-outs before I get back to my own code (and I never wanted to step in in this first place).
There always seems to be a _LIBCPP_DEBUG macro in view, as well as _LIBCPP_INLINE_VISIBILITY - but these seem to be everywhere so I'm not sure it's a correlation. It does seem plausible that it has something to do with the way inlining is working, though.
I've not been able to find any examples of anyone else with this problem - yet, for me, it has persisted across several betas - into the release - and through a complete reinstall of the OS.
Has anyone else even seen this? - but better still knows what's going on?
lldb in Xcode 4.5 doesn't handle stepping over inlined functions. The libc++ standard library has many functions that are always inlined, even when built at -O0, which makes this a problem. It looks like Jim Ingham worked on this about a month ago, e.g. see the first patch http://llvm.org/viewvc/llvm-project?view=rev&revision=163044 and several follow-on patches over the following week or two, but of course those aren't in a released version of lldb yet. You can build and use a command line version of lldb from the public site, http://lldb.llvm.org/ (see in particular http://lldb.llvm.org/build.html ), the only tricky bit is to remember to follow the code signing instructions in lldb/docs/code-signing.txt.
I've seen this too, and not only with libc++, also with libstdc++ (the GNU C++ standard library, used by GCC and by clang in C++03-mode). I've always figured it's due to inlining, which I guess sometimes happens in debug builds too.
来源：https://stackoverflow.com/questions/12651441/debugger-steps-deeper-when-trying-to-step-out-of-c11-std-lib