jmc@inset.UUCP (John Collins) (09/17/85)
I hit a nasty bug compiling a lex-generated program recently. The program
had statements of the form
return (x = y, constant);
where "constant" was > 256
I tracked it down to the compiler, where in cgram.y the constant is handled by
lines of the form
| ICON
{ $$ = bcon(0);
$$->tn.lval = lastcon;
......
the routine "bcon" in trees.c is supposed to work out the size required for
the constant - and in this case it always gives a char. Somewhere along the
line in a COMOP node the constant gets lopped down to a single byte.
There is a further bug in trees.c, in that the node is created with a 0 in
and the argument is not tested.
I see that later versions of the compiler drop the fiddling in bcon, but
retain the cgram.y code. They are also more careful in handling the COMOP
node later on.
In my version of the compiler I fixed 'bcon' and changed the cgram.y
statements to read
$$ = bcon(lastcon);
and the problem went away (and the compiler still works).
Any comments?
--
John M Collins ....mcvax!ist!inset!jmc
Phone: +44 727 57267
Snail Mail: 47 Cedarwood Drive, St Albans, Herts, AL4 0DN, England.