Re: [Patches] [patch] Fix for debug/tst-backtrace{5, 6} failure of 32-bit libc on 64-bit host

[Paul Pluzhnikov <ppluzhnikov@xxxxxxxxxx>]

On Mon, Feb 20, 2012 at 3:54 PM, Joseph S. Myers
<joseph@xxxxxxxxxxxxxxxx> wrote:

>> This failure is due to GCC laying out fn code like so:
>
> But I don't think the test should be changed here to allow no name for the
> function.  The libgcc unwinder knows to subtract 1 from a return address
> when unwinding (and knows not to do so in a signal frame), and subtracting
> 1 should get you within the function.  Maybe there is somewhere that logic
> is missing?

For what it's worth, "man backtrace" says:

  Each item in the array pointed to by buffer is of type void *, and is
  the return address from the corresponding stack frame.

Note that it says RA, and RA-1 ...

The man page and backtrace itself could of course be changed, but (I expect)
doing so will break many applications that are already doing -1 on return
addresses.

An alternate fix could be to re-try symbol @RA-1 if symbol @RA is empty
in tst-backtrace6.c.

Thanks,
-- 
Paul Pluzhnikov
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