Re: Any Suggestion How To Accomplish A Debug Macro?

["Randy Brukardt" <randy@rrsoftware.com>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:fh7u81n706kr.131btl9yj1iz8.dlg@40tude.net...
> On Fri, 02 Jan 2015 21:37:47 +0100, J-P. Rosen wrote:
...
> However, it would be interesting to consider how tracing could be better
> supported. I mean options:
>
> 1. To have zero-cost turned off tracing, e.g. some code modification
> techniques or maybe something else. After all we have zero-cost 
> exceptions,
> why not tracing.

But "zero-cost exceptions" aren't really zero-cost, they just shift the cost 
to handling. And that's already the case; virtually all of the cost of 
tracing is when the tracing is enabled. (A Boolean compare being about the 
cheapest operation on most targets.) About all one could do would be to keep 
the tracing code out of the normal flow, which would decrease paging/caching 
costs a bit when tracing is off -- but that would not make a noticable 
difference on the vast majority of programs. It would be unlikely to be 
worth the work.

> 2. Ideas for the compilation units structure modification which would 
> allow
> to have tracing code physically separated from the functional code.

We've considered such ideas in the context of assertions, but nothing 
proposed really looked like a proper part of Ada. For tracing, it would be 
even harder, because tracing can be inserted anywhere in the flow of a 
program (not just at particular places like most assertions). Moreover, in 
both cases, there isn't a clear-cut boundary between them (for tracing, 
that's primarily human-readable output, which often is needed anyway; for 
assertions, that's predicate functions that you might want to use to insert 
pre-tests before operations).

I use separate logging and trace management packages, which (combined with 
my aversion to use clauses) show tracing code pretty well. It's not clear at 
all that we could do better with syntax mechanisms.

                               Randy.