How to call std library functions in lldb

How does one print out an expression with a std library function in lldb? For example, suppose I want to use std::string::c_str() in an print expression. I can see the symbol and disassemble it just fine but cannot seem to use it in an expression call

(lldb) image lookup -v -r -n "c_str\("
2 matches found in /usr/lib/libc++.1.dylib:
        Address: libc++.1.dylib[0x0000000000041da6] (libc++.1.dylib.__TEXT.__text + 264214)
        Summary: libc++.1.dylib`std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::c_str() const
         Module: file = "/usr/lib/libc++.1.dylib", arch = "x86_64"
         Symbol: id = {0x000002ec}, range = [0x00007fff8ec8cda6-0x00007fff8ec8cdbe), name="std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::c_str() const", mangled="_ZNKSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE5c_strEv"



(lldb) dis -n "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::c_str()"
libc++.1.dylib`std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::c_str() const:
   0x7fff8ec8cda6:  pushq  %rbp
   0x7fff8ec8cda7:  movq   %rsp, %rbp
   0x7fff8ec8cdaa:  testb  $0x1, (%rdi)
   0x7fff8ec8cdad:  je     0x7fff8ec8cdb5            ; std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::c_str() const + 15
   0x7fff8ec8cdaf:  movq   0x10(%rdi), %rdi
   0x7fff8ec8cdb3:  jmp    0x7fff8ec8cdb8            ; std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::c_str() const + 18
   0x7fff8ec8cdb5:  incq   %rdi
   0x7fff8ec8cdb8:  movq   %rdi, %rax
   0x7fff8ec8cdbb:  popq   %rbp
   0x7fff8ec8cdbc:  retq   
   0x7fff8ec8cdbd:  nop    

But cannot seem to use it in an expression. Seems to always choke on the std namespace identifier

(lldb) expr std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::c_str($rax)
error: use of undeclared identifier 'std'
error: expected unqualified-id
error: 2 errors parsing expression

That's an instance method, you have to call it on an object. In your case, it looks like you want to do something like:

(lldb) expr ((std::__1::string *) $rax)->c_str()
(const value_type *) $1 = 0x00007fff5fbff661 "some string here"

You really shouldn't have to explicitly name the __1, but lldb doesn't support "inline namespaces" yet (and the clang debug information doesn't say __1 IS an inline namespace, so for now you do.