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

[Andrew Cagney <cagney at gnu dot 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