Re: [PATCH] Add a 'starti' command.

[John Baldwin <jhb@freebsd.org>]

On Thursday, August 31, 2017 11:51:33 PM Pedro Alves wrote:
> Hi John,
> 
> On 08/30/2017 12:54 AM, John Baldwin wrote:
> > This works like 'start' but it stops at the first instruction rather than
> > the first line in main().  This is useful if one wants to single step
> > through runtime linker startup.
> 
> I like the idea.  I actually once wrote a patch quite similar to this.
> I had called the command "create", inspired by "target_create_inferior".
> Is there a reason to actually set a breakpoint at the first instruction and
> run to it, actually?  My old prototype just created the inferior and
> didn't resume it all, see:
> 
>  https://github.com/palves/gdb/commits/create_command
> 
> though maybe going through normal_stop may be a good idea.

I had initially tried something like this (but without the print... line),
but GDB hung for me without printing a prompt and accepting more commands.
I assumed that there was some additional handling in proceed() that needed
to be done.  I would probably rather take this approach if it can be made
to work though.
 
> I agree with Keith - this should really have some tests.
> 
> For example:
> 
> - write a global constructor that sets a flag, and then check
>   that the flag is still clear when we're still at the entry point.
>   This can be either a C++ test or a C test using
>   __attribute__ ((constructor))-
> 
> - After creating the inferior, check that you can manually set
>   a break on main, and continue to it.
> 
> - Try backtrace, and check that only one frame comes
>   out.  That may expose buggy unwinders that don't stop
>   unwinding at the entry point currently, but then that
>   should be fixed anyway, since users will run into that
>   too.

Hmmm, these are a bit more interesting than the very simple test I've added
so far.  I'm not very fluent in writing tests yet, but I'll see what I can
come up with.

-- 
John Baldwin