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Re: Thread backtrace termination


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


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