Open Radar

 
Summary:
========
Creating an empty std::list of std::string (e.g. `std::list<std::string> groups;`) and running the program in optimisation mode -Os, it just crashes.

Steps to Reproduce:
1. Download the attached file test.mm as /tmp/test.mm
2. Compile it as follows:
    clang -o /tmp/test -Os -fsanitize=object-size -fsanitize-undefined-trap-on-error -framework Foundation -ggdb -lstdc++ /tmp/test.mm
3. Run it with
    /tmp/test
    
Expected Results:
================
Program exits and returns zero.

Actual Results:
===============
Program crashes with SIGILL.

The reason is that this:

   215 	    _LIBCPP_INLINE_VISIBILITY
   216 	    pointer __self()
   217 	    {
-> 218 	        return static_cast<pointer>(pointer_traits<__base_pointer>::pointer_to(*this));
   219 	    }
   220 	};

in C++ STM (/Applications/Xcode.app/Contents//Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/list) the line 218 comes out as a straight UD2 in the compiled output.

Also see the output of the disassembly:

$ otool -tV /tmp/test
/tmp/test:
(__TEXT,__text) section
_main:
0000000100000f9a    pushq	%rbp
0000000100000f9b    movq	%rsp, %rbp
0000000100000f9e    ud2

Regression:
===========
don't know

Notes:
======
The attached program in text form:
---
#include <string>
#include <list>

int main(int argc, char **argv)
{
    std::list<std::string> groups;
    return 0;
}
---