[Bug c++/62243] New: Non-typename template argument behaviour in loop (unsigned int)

[Bug c++/62243] New: Non-typename template argument behaviour in loop (unsigned int)

[bjodah at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62243

            Bug ID: 62243
           Summary: Non-typename template argument behaviour in loop
                    (unsigned int)
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bjodah at gmail dot com

I have come across something that puzzles me quite a bit, consider this small
program:

#include <iostream>

template <int w>
void f(){
    for (int i=-1*static_cast<int>(w); i <= w; ++i)
        std::cout << i << std::endl;
}

int main()
{
    f<3>();
    return 0;
}

which generates as expected output -3 to 2.
However changing the type of the non-type template argument to unsigned int,
i.e. `template <unsigned int w>` makes the program skip the loop. (g++ 4.8.2 &
clang++ 3.4)
Is this a bug in the compiler or is it the expected behaviour?

[Bug c++/62243] Non-typename template argument behaviour in loop (unsigned int)

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62243

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
i <= w if I and w are int then the compare is done in int but if w is unsigned
int, then it is done in unsigned int so (unsigned int)-3 is always greater than
3.

[Bug c++/62243] Non-typename template argument behaviour in loop (unsigned int)

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62243

--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> ---
Please always compile your programs with -Wall, it would have told you what was
wrong.

[Bug c++/62243] Non-typename template argument behaviour in loop (unsigned int)

[bjodah at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62243

--- Comment #3 from Bjoern Dahlgren <bjodah at gmail dot com> ---
Will do. Sorry for this and thank you.