Where does VMError::print_native_stack and os::get_sender_for_C_frame load/use the frame pointer?

[David Holmes]

Hi Julian,

On 8/07/2024 4:04 pm, Julian Waters wrote:
> Hi all,
> 
> I have a question with regards to os::get_sender_for_C_frame and
> VMError::print_native_stack. In Windows specific code comments allude
> to both needing the rbp register to be saved, which is why
> VMError::print_native_stack
> doesn't work on Windows since Microsoft Visual C doesn't save the frame
> pointer, as stated:
> 
> /*
> * Windows/x64 does not use stack frames the way expected by Java:
> * [1] in most cases, there is no frame pointer. All locals are addressed via RSP
> * [2] in rare cases, when alloca() is used, a frame pointer is used,
> but this may
> * not be RBP.
> * See http://msdn.microsoft.com/en-us/library/ew5tede7.aspx
> *
> * So it's not possible to print the native stack using the
> * while (...) {... fr = os::get_sender_for_C_frame(&fr); }
> * loop in vmError.cpp. We need to roll our own loop.
> */
> 
> // VC++ does not save frame pointer on stack in optimized build. It
> // can be turned off by -Oy-. If we really want to walk C frames,
> // we can use the StackWalk() API.
> 
> I can't seem to find where rbp is loaded and used on platforms and
> compilers that do save the frame pointer though. Eclipse cannot find
> it through the vast collection of member methods inside the frame
> class and related code. Do anyone by any chance know where the code that
> loads and uses the frame pointer for os::get_sender_for_C_frame and
> VMError::print_native_stack is located on such platforms?

Isn't this part of the ABI for these platforms, so the C/C++ compiler 
maintains them. ??

David
-----

> best regards,
> Julian