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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.


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