Re: Thread backtrace termination

[Jonathan Larmour <jifl@eCosCentric.com>]

Daniel Jacobowitz wrote:
> On Mon, Jul 11, 2005 at 06:52:13PM +0100, Jonathan Larmour wrote:
> 
>>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.
[snip]
> The error is caught in the top level code for the backtrace command;
> that effectively downgrades it to a warning and backtrace termination.

Ah ok, thanks.

>>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.
> 
> 
> What else would you suggest?  GDB is confused.  From its point of view,
> the stack _is_ corrupt.

It's possibly alarmist, but it's no big deal.

> Well, the patch was:[snip]
> You can find the discussion and sample use on gdb@ a month or two
> earlier.

Aha, yes, at 
http://sources.redhat.com/ml/gdb-patches/2005-03/msg00047.html and friends.

That seems interesting but somewhat unwieldy, and as you said before, 
wouldn't apply to compiler generated code.

>>>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?
> 
> 
> This is basically a convention.  You could, I suppose, patch a compiler
> to generate it.  I'm not sure that would be wise.

If someone were to come up with an __attribute__ that could be used with 
GCC to mark functions to be annotated this way, it might be possible. But 
it's beyond me (or at least, beyond what I have time to get up to speed 
with) and I doubt anyone else will be that interested. Ho hum.

>>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.
> 
> 
> *shrug* maybe.

Well, I'm prepared to create a patch to add such a command if people here 
think something with that principle would be accepted.

Jifl
-- 
eCosCentric    http://www.eCosCentric.com/    The eCos and RedBoot experts
--["No sense being pessimistic, it wouldn't work anyway"]-- Opinions==mine