Re: [PATCH] gdb/cli: if redirecting output, also redirect top-level interpreter's ui-out

[Pedro Alves <pedro@palves.net>]

On 10/6/20 4:40 PM, Tankut Baris Aktemur via Gdb-patches wrote:
> When executing commands from Python, the API provides an option to
> capture the command output in a string and return this to the user.
> See the `gdb.execute` function at
> 
>   https://sourceware.org/gdb/onlinedocs/gdb/Basic-Python.html#Basic-Python
> 
> When the `to_string` argument is True, the output of the executed
> command is supposed to be captured and returned to the caller.  For
> this, GDB temporarily redirects the ui-outs to a string file.
> 
> However, output does not get captured if the executed command prints
> its output through the top-level interpreter's ui-out.  E.g., in the
> following we still see the output being printed.
> 
>   (gdb) python gdb.execute("inferior 1", from_tty=False, to_string=True)
>   [Switching to inferior 1 [<null>] (<noexec>)]

Note this output is not really considered output of the command.
It's asynchronous output sent to all UIs in reaction to the
inferior-switching event.

If e.g., the top interpreter is MI (say, you run that python from a breakpoint
command), then you get:

 (gdb) 
 python gdb.execute("inferior 1", from_tty=False, to_string=True)
 &"python gdb.execute(\"inferior 1\", from_tty=False, to_string=True)\n"
 ~"[Switching to inferior 1 [<null>] (/home/pedro/gdb/binutils-gdb/build/gdb/gdb)]\n"
 ^done
 (gdb) 

And your patch won't capture that:

 python str=gdb.execute("inferior 1", from_tty=False, to_string=True)
 &"python str=gdb.execute(\"inferior 1\", from_tty=False, to_string=True)\n"
 ~"[Switching to inferior 1 [<null>] (<noexec>)]\n"
 ^done
 (gdb) 
 python print(str)
 &"python print(str)\n"
 ~"\n"
 ^done
 (gdb)