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Re: [RFA] linespec.c change to stop "malformed template specification" error
Elena Zannoni <ezannoni@cygnus.com> writes:
> > Operators like '<' can appear in template arguments. For example, you
> > could define a template like this:
> >
> > template <int i> struct list { int a[i], b[i]; };
> >
> > and then use it like this:
> >
> > struct list <20> l;
> >
> > and you get the same thing as if you'd written:
> >
> > struct { int a[20], b[20]; } l;
> >
> > At least I think so, anyway. I don't really know C++. But the point
> > is, those template arguments can be any arbitrary constant expression.
> > So I could have a template invocation like this:
> >
> > struct list < (x < y) ? 10 : 20 > l;
> >
> > So how does our poor little decode_line_1 handle that? Basically, we
> > need to replace decode_line_1 with a real parser.
>
> I am not sure that decode_line_1 will ever be invoked in such a case.
> Looking at when it's called, it seems to be only when you specify
> a location, not an expression, and that occurs for 'break blah' and
> 'list blah' only.
Templates can expand to functions, too:
template <int i>
int add_const (int j)
{
return i + j;
}
then, add_const <4> (3) returns 7.
But add_const <4> and add_const <5> are different functions. The
compiler emits separate code for each of them. So you need to be able
to set a breakpoint on add_const <4>. And the template argument to
add_const can be any constant expression.
So finding breakpoint names requires parsing (almost) arbitrary expressions.