https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63645
Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #7 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to M Welinder from comment #5)
> You guys are trigger happy.
>
> > Your union simply takes more space than your GnmExprBinary struct
>
> Of course it does! The union requires space that is large enough
> for its largest member, so having a smaller member is going to be
> the case in 99% of unions and the standard has no objections.
> If you think otherwise, a reference to the standard would be nice.
>
> To show that the size difference is irrelevant, simply change
> GnmExprBinary to
>
> typedef struct {
> guint8 oper;
> int argc;
> GnmFunc *func;
> } GnmExprBinary;
>
> whereupon GnmExprBinary, GnmExprFunction, and GnmExpr all take up the
> same amount of space.
Or adjust your malloc, which is simply too small in your orginal testcase.
> We still get this error from valgrind.
>
> ==6201== Conditional jump or move depends on uninitialised value(s)
> ==6201== at 0x4005F8: test (vvv.c:38)
> ==6201== by 0x4004D8: main (vvv.c:49)
That is a different issue. You access expr->func.argc and expr->func.func
in your if expression. And of course they are uninitialised.
