status of Programming by Contract (PEP 316)?
ricaraoz at gmail.com
Sat Sep 1 02:04:49 CEST 2007
Neil Cerutti wrote:
> On 2007-08-31, Ricardo Aráoz <ricaraoz at gmail.com> wrote:
>> Russ wrote:
>>> Yes, thanks for reminding me about that. With SPARK Ada, it is
>>> possible for some real (non-trivial) applications to formally
>>> (i.e., mathematically) *prove* correctness by static analysis.
>>> I doubt that is possible without "static declarative type-
>>> SPARK Ada is for applications that really *must* be correct or
>>> people could die.
>> I've always wondered... Are the compilers (or interpreters),
>> which take these programs to machine code, also formally proven
>> correct? And the OS in which those programs operate, are they
>> also formally proven correct? And the hardware, microprocessor,
>> electric supply, etc. are they also 'proven correct'?
> Who watches the watchmen? The contracts are composed by the
> programmers writing the code. Is it likely that the same person
> who wrote a buggy function will know the right contract?
Actually my point was that if a program is to be trusted in a critical
situation (critical as in catastrophe if it goes wrong) then the OS, the
compiler/interpreter etc should abide by the same rules. That is
obviously not possible, so there's not much case in making the time
investment necessary for correctness proof of a little program (or
usually a little function inside a program) when the possibilities for
failure are all around it and even in the code that will run that
function. And we should resort to other more sensible answers to the
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