Hi

     I start working on making recently added constexpr tests to work in 
Debug mode.

     It appears that the compiler is able to detect code mistakes pretty 
well as long we don't try to hide the code intention with a defensive 
approach. This is why I'd like to propose to replace '__n > 0' 
conditions with '__n != 0'.

     The result is demonstrated by the constexpr_neg.cc tests. What do 
you think ?

     * include/bits/stl_algobase.h (__memmove): Return _Tp*.
     (__memmove): Loop as long as __n is not 0.
     (__copy_move<>::__copy_m): Likewise.
     (__copy_move_backward<>::__copy_move_b): Likewise.
     * testsuite/25_algorithms/copy/constexpr.cc: Add check on copied 
values.
     * testsuite/25_algorithms/copy_backward/constexpr.cc: Likewise.
     * testsuite/25_algorithms/copy/constexpr_neg.cc: New.
     * testsuite/25_algorithms/copy_backward/constexpr.cc: New.

     I'll submit the patch to fix Debug mode depending on the decision 
for this one.

François