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Re: Always use SVN_ERR_ASSERT [was: svn commit: r1329234 - in /subversion/trunk: ./ subversion/libsvn_delta/compat.c]

From: Julian Foad <julianfoad_at_btopenworld.com>
Date: Mon, 23 Apr 2012 20:40:59 +0100 (BST)

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.

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.

- Julian
Received on 2012-04-23 21:41:36 CEST

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