Re: assert vs. std::logic_error?
* Roland Pibinger:
On Fri, 23 Nov 2007 09:31:14 +0100, "Alf P. Steinbach" wrote:
* Roland Pibinger:
asserts and tests are not related. Production code which is tested
contains no assets.
That's a good way to transform easily identifiable bugs into more
nebulous general "instability".
Any real-world example for programs that ships with asserts?
Hm, let's see, the program I'm using to type this? Just to take the
first one that comes to mind, since it's right in front of me. For your
convenience I now googled "Thunderbird assert error", clicked on first
hit, and there you have it, <url:
http://bugs.opensolaris.org/view_bug.do;jsessionid=de960c54a06d20accda05f27018?bug_id=6429104>.
Another argument against asserts in production code is performance:
asserts significantly slow down the program (if they don't you haven't
used enough asserts in your code).
Sorry, that's mostly bullshit, in the technical meaning of bullshit. A
slowdown due to assertions means you're using assertions incorrectly, to
check too complicated stuff. Like checking an invariant of a
complicated data structure by traversing it, for every operation. An
assertion tells what you think must be true at a given point, but there
is almost infinitely much than one thinks must be true, and it's
misguided to try to assert it all: an assertion is for critical stuff
that is relevant at the point of the assertion.
But, that brings up an important point, also mentioned by James Kanze
else-thread (I think).
Namely that there is a runtime cost associated, an engineering
trade-off, and so you really want to have an assertion system in place
where you can shut down the most costly ones. Checking
costly-to-compute invariant of data structure all the time isn't
meaningful after that class or set of classes has been debugged and
tested, but leaving more inexpensive asserts in place is meaningful,
because it can catch remaining logic bugs.
BTW, asserts seem to be a C and C++ only thing. For my work I mostly
use Java and I have neither used nor missed asserts. They are not
necessary in that environment.
Try to google up "java assert".
Cheers, & hth.,
- Alf
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