Setjmp(), longjmp() in gnuplot

[<tim...@en...>]

Hello !

I keep working on the wxwidgets terminal, and I am now facing a=20
difficult problem.

When there are errors on a command line, gnuplot uses its functions=20
int_error(token, string) to inform the user and stop parsing the command=20
line. This function prints an error message and then calls=20
bail_to_command_line() which is simply a wrapper for the standard=20
longjmp(env) function. This is similar to "goto", and puts the program=20
in its initial state by restoring the registers set in main().

As far as I understand, this would be perfect if I had not to use a=20
separate thread for my terminal. Indeed, I want to send a command from=20
the terminal (through a menu for example) to gnuplot. I use events=20
defined in mouse.c, and more precisely a "command" event (which doesn't=20
seem to be used very often, or maybe in OS/2 only). The do_event(event)=20
is executed in my gui thread. When an error appears on the command, we=20
obtain a longjump which is invalid for *this* gui thread... and it ends=20
with a segmentation fault.

I can't simply delete the longjump, as it is necessary to stop command=20
line parsing. If I do it, gnuplot either seems to enter in a infinite=20
loop or terminante with an other segfault.

Of course, there's a solution : avoid any error in commands sent from my=20
terminal. But it's like reinventing the wheel. (These errors can be=20
various : for example, if I write a dialog to "set xlabel", and the user=20
enters forbidden characters; or I want to send a "replot" while it's the=20
"test" command which has opened the terminal, etc.)

Another solution would be to build the terminal as a separate process,=20
like x11 or os/2 ones. But I think it's not an optimal design.

So I would be pleased if somebody can give me a tip in order to deal=20
with this issue ;-) .

On my side, I will look more thoroughly to existing code to see how=20
things are done (by windows gui, os/2 pm, etc. )

Greetings,
Timoth=E9e