[Dave Rich, concerning a constraint prototype that lacks an implementation] > This is either a compile/elaboration error, or it is not an error. Right. It seems that implementations have converged on the permissive approach - I'm guessing there has been some user pressure there - and the meaning is fairly clear; an unimplemented constraint is presumably the same as constraint foo {1;} and has no effect. This all seems quite sensible to me, but I agree with the existing implementations: it likely represents a user oversight, and should evince a warning. However, it's also evident that different tools regard the constraint prototype in different lights. One simulator clearly thinks of the constraint prototype as being, in effect, a "pure virtual" that is OK in an abstract class but should be overridden in any concrete derived class. Other simulators give the warning for an unimplemented constraint prototype even when it appears in an abstract class. I'm inclined to support the "pure virtual" position, but it may have repercussions I haven't thought of. In particular, it tangles the syntax of derived-class constraints with that of out-of-block constraints. Advice please? -- Jonathan Bromley Consultant Doulos - Developing Design Know-how VHDL * Verilog * SystemVerilog * SystemC * PSL * Perl * Tcl/Tk * Project Services Doulos Ltd. Church Hatch, 22 Market Place, Ringwood, Hampshire, BH24 1AW, UK Tel: + 44 (0)1425 471223 Email: jonathan.bromley@doulos.com Fax: +44 (0)1425 471573 http://www.doulos.com -------------------------------------------------------------------------------- Doulos Ltd is registered in England and Wales with company no. 3723454 Its registered office is 4 Brackley Close, Bournemouth International Airport, Christchurch, BH23 6SE, UK. This message may contain personal views which are not the views of Doulos, unless specifically stated. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.Received on Tue Apr 21 05:09:46 2009
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