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Re: [patch] Remove invalid test on non-const empty strings


Paolo Carlini wrote:

Chris Jefferson wrote:

As we are testing empty strings, size()==0. Therefore we can only perform the operation "s[0]" where s is the empty string when s is const (when s[0] will return charT()). When s is non-const the operation is undefined. The test tries to access s[0] on an empty string s on both const and non-const strings. Therefore this patch fixes things up.


I see your point, but I think the issue is somewhat debatable, and much more general, actually. In this sense: according to 21.3.4, as you point out above, "the behavior is undefined". Now, it happens, that, *given our current implementation*, if things are not broken, we mus return '\0' in this case too.

Therefore, the general issue is the following: should our testsuite only test what the standard mandates or, when appropriate, request, so to speak, "more" from the code, for instance specific behaviors when the behavior is strictly speaking undefined? I don't think we have a very rigorous policy about this issue and, frankly, being an implementor that cares about *regressions* and *unexpected* changes of behavior, that is not being a seller of a "conformancy testsuite", I think the latter interpretation has its own advantages, in some cases.

What do other people think?

Good point!

Perhaps then a better idea would be to wrap tests like this in a #ifndef _GLIBCXX_DEBUG / #endif pair?


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