[Bug c++/52567] New: constant expression not recognized as being constant

[Bug c++/52567] New: constant expression not recognized as being constant

[l_belev at yahoo dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52567

             Bug #: 52567
           Summary: constant expression not recognized as being constant
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: l_belev@yahoo.com


when trying to compile the following simple c++ code fragment, gcc gives error 
"error: field initializer is not constant"

class RSpans {
    public:
    static const int max_span = (1<<31)-1;
};

[Bug c++/52567] constant expression not recognized as being constant

[marc.glisse at normalesup dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52567

--- Comment #1 from Marc Glisse <marc.glisse at normalesup dot org> 2012-03-12 18:10:16 UTC ---
1<<31 overflows and is thus not a constant. Try maybe 1LL<<31 ?

[Bug c++/52567] constant expression not recognized as being constant

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52567

Paolo Carlini <paolo.carlini at oracle dot com> changed:

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

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-03-12 18:28:55 UTC ---
Or even 1U, afaics.

[Bug c++/52567] constant expression not recognized as being constant

[l_belev at yahoo dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52567

--- Comment #3 from Luchezar Belev <l_belev at yahoo dot com> 2012-03-12 20:56:10 UTC ---
It overflows alright, but what this has to do with not being constant?

An overflow in a constant expression makes it variable? I fail to see the logic
here

[Bug c++/52567] constant expression not recognized as being constant

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52567

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-03-12 20:59:39 UTC ---
An overflow in an integer expression is never an integer constant expression.

[Bug c++/52567] constant expression not recognized as being constant

[l_belev at yahoo dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52567

--- Comment #5 from Luchezar Belev <l_belev at yahoo dot com> 2012-03-12 21:08:07 UTC ---
Ok, but at least the error message should be changed to tell about overflow.

For example the following code gives error too, but it says
"error: overflow in constant expression"
which is more clear

int foo(int x) {
    switch (x) {
    case 1: return 5;
    case (1<<31)-1: return 7;
    }
}