SUB arguments use-before-define

[nigoroll]

SUB arguments currently can only be used after being defined. E.g. this works:

sub foo { }
sub caller {
  some.vmod(foo);
}

but this does not:

sub caller {
  some.vmod(foo);
}
sub foo { }

[dridi]

Isn't this the case with other symbols too? (backend, acl, anything named)

[nigoroll]

exactly. But call sub instantiates sub, so I wonder if use as an argument should do the same

[dridi]

It's actually not true that anything named can be defined after use. It's only true for a subset of the VCL parsing like the call action or the IP ~ operator.

With this test case snippet:

varnish v1 -vcl {
        sub vcl_recv {
                set req.backend_hint = b;
        }
        backend b { .host = "${localhost}"; }
}

I get this:

**** v1    CLI RX|Message from VCC-compiler:
**** v1    CLI RX|Symbol not found: 'b'
**** v1    CLI RX|At: ('<vcl.inline>' Line 4 Pos 40) -- (Pos 40)
**** v1    CLI RX|                set req.backend_hint = b;
**** v1    CLI RX|---------------------------------------#-
**** v1    CLI RX|
**** v1    CLI RX|Running VCC-compiler failed, exited with 2
**** v1    CLI RX|VCL compilation failed
---- v1    VCL compilation failed expected success

I think we could generalize "defined after use" for all types that need to be referenced when used via a symbol:

• ACL
• BACKEND
• PROBE
• SUB

If we agree on doing that, I would implement this special case with a new field in struct type.

[dridi]

#3613