maybe_warn_shift_overflow is checking for patterns such as (1 << 31)
and not warning for them.
However, if the shifted value is negative, a shift by a non-zero
amount will always shift *out* of the sign bit rather than into it.
Thus it should be warned about, even if the value only requires
one bit more than the precision of the LHS.
Ok for trunk?
Paolo
gcc:
* c-family/c-common.c (maybe_warn_shift_overflow): Warn on all
overflows if shifting 1 out of the sign bit.
gcc/testsuite:
* c-c++-common/Wshift-overflow-1.c: Test shifting 1 out of the sign bit.
* c-c++-common/Wshift-overflow-2.c: Test shifting 1 out of the sign bit.
* c-c++-common/Wshift-overflow-3.c: Test shifting 1 out of the sign bit.
* c-c++-common/Wshift-overflow-4.c: Test shifting 1 out of the sign bit.
* c-c++-common/Wshift-overflow-6.c: Test shifting 1 out of the sign bit.
* c-c++-common/Wshift-overflow-7.c: Test shifting 1 out of the sign bit.