Re: Unable to step over (n and ni) on mipsel-linux...

[Andrew Cagney <cagney@gnu.org>]

> Andrew Cagney wrote:
> 
>>>>>GNU gdb 6.2_2004-08-19-cvs
>>>>>
>>
>>>>from the gdb_6_2-branch yesterday.
>>
>>>>>
>>>>>../gdbcvs/src/configure  --build=i686-pc-linux --host=mipsel-linux
>>>>>--target=mipsel-linux --enable-tui=no
>>>>>
>>>>>Most of the time when I do next or nexti, gdb is treating it as if I did
>>>>>step or stepi.
>>>>>
>>>>>I have tracked the problem down to this portion of code:
>>
>>> 
>>> 
>>> Sounds like a bug in the MIPS unwind code.  Can you build/test with 
>>> mainline (the fixes won't be backported).
>>> 
> 
> 
> I will try the mainline soon.

Thanks.
> 
>>> The problem is that, after the step-into the callee, the MIPS unwind 
>>> code is not correctly unwinding back to the caller's frame-ID.  As 
>>> Theodore notes, this is very compiler dependant.
>>> 
> 
> 
> Currently GDB examines the next instruction to see if it is a branch (or
>   jal or jalr..) to see where to place a temporary breakpoint for single
> stepping.

> Instead of stepping into a function and checking to see if we are in a
> different frame (settting a breakpoint at the return address location),
> why not set the breakpoint at the return location before making the
> function call?

That would mean examining every instruction to determine if it is a call 
- effectively s/w single step.  GDB tries to do avoid doing that so that 
single-step is faster.

> By compiler dependant, do you mean the compiler GDB was built with, or
> the one that compiled the target code?

For you mipsel-linux-gcc (the one that compiled the target code).

Andrew

> 
> 
>>> Andrew
>>> 
>>> 
> 
> 
> 
>