Julian Foad wrote on Mon, Apr 23, 2012 at 20:40:59 +0100:
> Daniel Shahaf wrote:
>
> > Julian Foad wrote:
> >> I (Julian Foad) wrote:
> >> > There isn't currently an easy build switch (such as NDEBUG) to disable
> >> > SVN_ERR_ASSERT completely at compile time. That's just a side issue. If
> >> > you want such a switch, just ask; we can easily create one. Or if you think we
> >> > need two levels of assertions -- one for quick tests and another for slow tests
> >> > -- and want to be able to compile-out the slow ones independently of the quick
> >> > ones, just ask. But implying we should use 'assert' for slow tests and
> >> > 'SVN_ERR_ASSERT' for quick tests is the Wrong Way.
> >>
> >> We can also introduce run-time control of whether the conditions are
> >> evaluated: test a global 'assertions enabled?' variable or function
> >> before evaluating the condition. For example:
> [...]
> > That doesn't sound right. Surely we don't want to allow disabling _all_
> > uses of SVN_ERR_ASSERT() this way? (Remember that some of them
> > translate to segfaults (possibly corruptions?) if the condition doesn't
> > hold)
>
> Hi Daniel.
>
> In places where there will be a seg-fault if the condition is false,
> the assertion statement doesn't prevent abnormal program termination,
> it only makes it easier to see what went wrong.
>
SVN_ERR_ASSERT() prevents an abnormal termination when a non-default
malfunction handler has been installed.
> In places where the processing will continue with wrong data or wrong
> behaviour if the condition is false, the assertion statement doesn't
> prevent the program from going wrong, it just changes the failure mode
> to a more obvious one.
>
> People who don't care about the failure mode in such cases may wish to
> turn off the checks.
>
Depends, I think. If libsvn_ra asserts that a log message is in UTF-8,
it is reasonable to want to disable that since the only harm resulting
is an svn_error_create() on the server. But if libsvn_fs asserts the
sanity of a revision before committing it, I think most people will
prefer to have the commit attempt fail.
(The latter example is not realistic since, at least in FSFS, we
generally return an svn_error_t rather than an assertion when a sanity
check fails.)
> - Julian
Received on 2012-04-23 22:00:45 CEST