Thread backtrace termination
Jonathan Larmour
jifl@eCosCentric.com
Mon Jul 11 17:52:00 GMT 2005
Daniel Jacobowitz wrote:
> On Mon, Jul 11, 2005 at 05:20:55PM +0100, Jonathan Larmour wrote:
>
>>The two "global constructors keyed to cyg_scheduler_start" lines are bogus
>>frame entries, although those also happened with GDB 6.1. The "corrupt
>>stack" whinge is new, and is treated as an error, including terminating
>>gdbinit scripts etc.
>
>
> This is already changed in CVS.
Okay. I haven't seen that. It still looks like an error to me in frame.c.
BTW, my other web searches seem to indicate that a fair few (naive) people
are thinking they are having stack corruption because GDB thinks there
might be. That's unfortunate.
>>I'd be interested if someone could clarify to me what
>>the termination conditions for a backtrace actually _are_. i.e. as an OS
>>author, how do I initialise a thread context to persuade GDB to stop when
>>it reaches the innermost frame.
>
> In general there's no defined way to do this. If the start routine is
> written in assembly, take a look at the example I posted earlier this
> year of using dwarf2 unwind information to terminate a backtrace by
> marking the return address column as undefined. There's a matching GDB
> patch, which was committed to HEAD after 6.3.
I've had a search for this and not found anything. I'm probably just not
using the right terms. Do you have a pointer, time frame or some search
terms I can use to pin this down? Thanks.
> For compiler-generated code there's really no useful way to do this.
I guess atleast now I know that, which saves me spending more time.
Wouldn't it make sense to make such a convention though, such as having a
return address of 0?
Alternatively, how about adding a new command that allows you to define a
set of entry point symbol names? People can then put an appropriate list
for themselves or their OS in ~/.gdbinit. Or it can be pre-initialised by
the OS support within GDB if there is one. e.g. nm-linux.h. Here's what
I'm thinking of:
set entry-point-name-list main _start _entry
Although handling mangled symbols and multiple languages might be fun. I'm
not an expert on such things.
Thanks,
Jifl
--
eCosCentric http://www.eCosCentric.com/ The eCos and RedBoot experts
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