Using gdb (windows popping up)

[jonetsu]

Hello,

I'm trying to simply get a debug session going on in a minimal way that
is, gdb in one buffer (window) and the source in the other buffer
(window), both being displayed side by side.  Simple enough, and the
customize-variable gdb-show-main set to non-nil allows just for this to
happen.

The gdb session starts (M-x gdb) with on the left gdb and on the right
the source.  In the source a breakpoint can be placed in the margin.
All fine, looks very good...

... until the debugging session starts.  At which point emacs decides
to create a new whole emacs app/window with the source code in it.  It
boldly replaces the source window with the debugged app's output window
and throws the source into a new emacs instance.

But the source code was already displayed and a breakpoint was set in
it showing that it is active and linked to gdb.  Why do that ?  If you
really want to show the output window, why not split the gdb window ?
Or maybe totally forget about the output window until the user wants
it ?  

Or is there a variable or two to control this ?  I read through the
documentation and did not find anything so far.  I would just like to
establish a clean working state with emacs and gdb in which things are
not popping up unexpectedly in new instances of emacs.  Emacs version
is 26.1.  Speedbar is not used in this case.

Cheers.