[Bug c/65830] New: -Wno-shift-count-negative -Wno-shift-count-overflow don't work with const ints

mpolacek at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Tue Apr 21 13:02:00 GMT 2015


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65830

            Bug ID: 65830
           Summary: -Wno-shift-count-negative -Wno-shift-count-overflow
                    don't work with const ints
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org

When dealing with const ints, the warning can't be suppressed with
-Wno-shift-count-negative -Wno-shift-count-overflow.

A c-c++-common/ test case:

/* PR c/... */
/* { dg-do compile } */
/* { dg-options "-O -Wno-shift-count-negative -Wno-shift-count-overflow" } */

int
foo (int x)
{
  const int a = sizeof (int) * __CHAR_BIT__;
  const int b = -7;
  int c = 0;
  c += x << a;    /* { dg-bogus "left shift count >= width of type" } */
  c += x << b;    /* { dg-bogus "left shift count is negative" } */
  c += x >> a;    /* { dg-bogus "right shift count >= width of type" } */
  c += x >> b;  /* { dg-bogus "right shift count is negative" } */
  return c;
}



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