First, the debugger IDE must be able to display multiple arrows, as
though there were multiple program counters in each function call.
The reason for this, is because parsing proceeds over sets of rules,
with a parsing position marked in each of them. (This is the stuff
displayed in the Bison generated .output file of each state.)
We could surely modify GDB and gdb-ui.el to do that.
Second, IDE's are often limited at displaying only one position per
input source code line.
I don't understand that sentence.
This would be insufficient for displaying a
parsing position in each grammar rule of the .y file, which normally
has several symbols on the same line. So here, one needs an arrow
pointing between the grammar symbols of each active rule.
We could surely modify GDB and gdb-ui.el to do that.
