[PATCH] Help compiler detect invalid code

[François Dumont]

Hi

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

 Â Â Â  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'.

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

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

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

François

-------------- next part --------------
A non-text attachment was scrubbed...
Name: constexpr_algo.patch
Type: text/x-patch
Size: 8214 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20190919/4480572f/attachment.bin>