Re: [Caml-list] Detecting missed checks for error indications in ML code

[Hendrik Boom <hendrik@topoi.pooq.com>]

On Sun, Jan 24, 2021 at 12:42:23PM +0100, Markus Elfring wrote:
> Hello,
> 
> OCaml belongs also to the category of functional programming languages.
> Thus the last expression in a function usually becomes the result of
> the data processing which was specified in a ML source file.
> This would usually happen also if the return value from a function call
> indicates an error code (when a function implementation does not throw an exception
> according to an error situation).
> 
> I got the impression that corresponding error checks can occasionally be missing.
> How do you think about to detect such cases by advanced source code analysis?

Hard to do without knowing how the function encodes error information in its 
return value.  For example, is it success or failure that it indicates by 
returning the value zero?

A ver simple approach is to return a disjoint union -- a choice between 
a valid valid or an invalid value of another type.  THen, of course, the 
compiler's type checker will prevent any use of the valid value without a 
check being performed.

-- hendrik