[Bug c++/54194] New: GCC 4.8 gives misleading suggestion about arithmetic in operand of '|'

[csaba_22 at yahoo dot co.uk]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54194

             Bug #: 54194
           Summary: GCC 4.8 gives misleading suggestion about arithmetic
                    in operand of '|'
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: csaba...@yahoo.co.uk


Using gcc version 4.8.0 20120806 (experimental) (GCC),
Target: x86_64-unknown-linux-gnu

to compile the following code:

int main()
{
char in[4]={0}, out[6];
out[1] = in[1] & 0x0F | ((in[3] & 0x3C) << 2);
}

results in a misleading warning (misplaced caret):

$ g++-48 -c -Wall -Werror w.cc
w.cc: In function 'int main()':
w.cc:4:45: error: suggest parentheses around arithmetic in operand of '|'
[-Werror=parentheses]
 out[1] = in[1] & 0x0F | ((in[3] & 0x3C) << 2);
                                             ^

The problematic operand is the left operand of '|', but the caret appears to be
pointing at the right operand.

For example, clang version 3.2 (trunk 161319) gives
$ clang++ -c -Wall -Werror w.cc
w.cc:4:16: error: '&' within '|' [-Werror,-Wbitwise-op-parentheses]
out[1] = in[1] & 0x0F | ((in[3] & 0x3C) << 2);
         ~~~~~~^~~~~~ ~
w.cc:4:16: note: place parentheses around the '&' expression to silence this
warning
out[1] = in[1] & 0x0F | ((in[3] & 0x3C) << 2);
               ^
         (           )