Re: assert vs. std::logic_error?
On Nov 21, 8:25 pm, Erik Wikstr=F6m <Erik-wikst...@telia.com> wrote:
On 2007-11-21 16:54, werasm wrote:
Care to share your thoughts on this, or point me to
some thoughts already shared.
My thoughts are like this (from a systems point of view):
When I have logic errors outside of my system (or software)
boundaries I throw a logic error (interface specification
not met, etc). This implies the system is logically
erroneous. I do not regard things like failure to read files
or access hard- ware in this light. For those I use runtime
error (but that steers from the question).
When I have errors due to requirements change inside my
software boundaries that cause code to break, I assert. I
try and do this in code that I know will be tested (this may
be hard to determine, but typically startup code).
Apart from above mentioned, I'm still on two minds on the topic.
Any other thoughts welcome.
The way I see it an assert should only trigger if there is
something wrong with your code and an exception should be
thrown if something goes wrong during the execution. In other
words, you use asserts to check the invariants that your code
should preserve. As Alan said: a triggered assert indicates a
bug.
I think his problem is more semantic. The name logic_error
sounds very much like a programming error, which should usually
be handled by an assert, and not an exception.
Roughly speaking, I tend to think of the opposition logic_error
vs. runtime_error as something like domain_error vs.
range_error. It is a logic_error to call sqrt() with a negative
value, a runtime_error if exp() overflows. Depending on
context, either or both can be considered as a programming error
(and thus should be handled by an assert)---the programmmer
didn't sufficiently validate his input. In practice, however, I
can imagine that there are cases where catching the exception is
the simplest way of validating the input: rather than an
explicit test up front (which could be extremely complicated, if
the later processing involves complex expressions or a lot of
iteration), just catch the exception, and do whatever you would
have done if the input didn't validate. (Now if only the math
routines were guaranteed to generate such exceptions:-).)
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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