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

[Paolo Carlini]

Jonathan Wakely wrote:

>Debug mode was written to the letter of the standard, not including any
>v3 extensions. IMHO this makes it very useful, in the same way as
>-ansi -pedantic, for checking you haven't made any assumptions that
>aren't guaranteed by the standard.
>  
>
I think this is an "obvious" but at same time crucial observation, in 
this sense:
the concepts of "regression testsuite" and of "debug-mode" are *different*.

The first one, as we already discussed, serves the purpose of avoiding 
regressions
and point out as soon as possible (unexpected) changes of behavior, very 
often
beyond what the standard says. Indeed, very often, in the compiler area 
but also
in the library area, fixes and improvements are accompanied by tweaks to 
*existing*
testcases, if only to change expected error messages. This is ok, from 
the regression
testsuite point of view.

Therefore, all in all, I believe it's a mistake trying at any cost to 
obtain a clean
regression testsuite in debug mode. At the very least we should think more
about the issue and the real meaning of the two concepts.

In my opinion, our attitude as C++ runtime library writers should be not 
much
different than the attitude of normal users, wrt "debug-mode": an useful 
help to
find non-portable assumptions and real errors in our code, nothing less, 
nothing
more. In particular, should not change the way we write regression tests.

Paolo.