backtrace() vs. _Unwind_Backtrace()

Fri Dec 5 16:39:00 GMT 2003

>>>>> On Fri, 5 Dec 2003 10:46:47 +0000, Andrew Haley <aph@redhat.com> said:

 Andrew> David Mosberger writes:
 >> While debugging another problem, I noticed that libjava currently
 >> attempts to use libc's backtrace() function to create a stack
 >> trace (libjava/gnu/gcj/runtime/natStackTrace.cc). Recently,
 >> libgcc got an _Unwind_Backtrace() function, which I think should
 >> do exactly what's needed there (in combination with
 >> _Unwind_GetIP()), so I think it would make sense to switch to
 >> _Unwind_Backtrace() instead.
 Andrew> Java uses backtrace() a lot, and _Unwind_Backtrace() is
 Andrew> inefficient. I see no good reason to switch unless
 Andrew> backtrace() doesn't work on a given target.
But in that case, HAVE_BACKTRACE should be turned on for ia64 Linux.
Older versions of libc have a broken backtrace() on that platform,
but even that can be worked around by doing:
	LD_PRELOAD=/usr/lib/libunwind-ia64.so.1
and with newer versions of libc, backtrace() will use _Unwind_Backtrace().
(And the libunwind-based _Unwind_Backtrace() is probably about as efficient
as it gets.)
	--david