How to get address of base stack pointer

Question

I am in the process of porting an application from x86 to x64. I am using Visual Studio 2009; most of the code is C++ and some portions are plain C. The __asm keyword is not

Answer 1

There is no guarantee that RBP (the x64's equivalent of EBP) is actually a pointer to the current frame in the callstack. I guess Microsoft decided that despite several new general purpose registers, that they needed another one freed up, so RBP is only used as framepointer in functions that call alloca(), and in certain other cases. So even if inline assembly were supported, it would not be the way to go.

If you just want to backtrace, you need to use StackWalk64 in dbghelp.dll. It's in the dbghelp.dll that's shipped with XP, and pre-XP there was no 64-bit support, so you shouldn't need to ship the dll with your application.

For your 32-bit version, just use your current method. Your own methods will likely be smaller than the import library for dbghelp, much less the actual dll in memory, so it is a definite optimization (personal experience: I've implemented a Glibc-style backtrace and backtrace_symbols for x86 in less than one-tenth the size of the dbghelp import library).

Also, if you're using this for in-process debugging or post-release crash report generation, I would highly recommend just working with the CONTEXT structure supplied to the exception handler.

Maybe some day I'll decide to target the x64 seriously, and figure out a cheap way around using StackWalk64 that I can share, but since I'm still targeting x86 for all my projects I haven't bothered.