[python] Allow explicit locations in breakpoints.

[Simon Marchi]

On 2017-10-16 02:23 PM, Simon Marchi wrote:
> I think for Python it would make sense to support the two paradigms.  If you
> are writing a Python command that ends up installing a breakpoint, it would
> be nice if you could directly pass what you received to the gdb.Breakpoint
> constructor and have it parse it (including explicit locations).  For example,
> 
>   (gdb) special-break -file foo.c -line 17
> 
> But it would also be nice to have a keywords based API, for when the line/file/function
> information is already split.  It would avoid having to build an explicit linespec
> string just to have GDB parse it after.
> 
> In terms of API, I think the "spec" argument could be mutually exclusive with
> the function/file/line/etc keywork arguments, which would be added.  An error
> would be thrown if you try to use both ways at the same time.
> 
> About the line="+3" issue, because this is Python, the line keyword could
> probably accept integers and strings.  And if it's a string, there could
> be some validation on the format.
> 
> Simon

Btw, if we went with the idea described above, I think your patch would be
acceptable as-is, and the work to do add keyword arguments could be done separately
(by you or somebody else).

Simon