On 12/11/15 11:09 -0700, Martin Sebor wrote:
On 11/12/2015 10:08 AM, Jonathan Wakely wrote:
On 12/11/15 08:48 -0700, Martin Sebor wrote:
On 11/11/2015 02:48 AM, Jonathan Wakely wrote:
As described in the PR, we have operator~ overloads defined for
enumeration types which produce values outside the range of valid
values for the type. In C++11 that can be trivially solved by giving
the enumeration types a fixed underlying type, but this code needs to
be valid in C++03 too.
This patch defines new min/max enumerators as INT_MIN/INT_MAX so that
every int value is also a valid value for the bitmask type.
Does anyone see any problems with this solution, or better solutions?
Just a minor nit that the C-style cast in the below triggers
a -Wold-style-cast warning in Clang, in case libstdc++ tries
to be Clang-warning free. Since the type of __INT_MAX__ is
int it shouldn't be necessary.
+ _S_ios_fmtflags_min = ~(int)__INT_MAX__
That's worth fixing, thanks.
Any suggestions for how to test this, given that GCC's ubsan doesn't
check for this, and we can't run the testsuite with ubsan anyway?
Use a case/switch statement with -Werror=switch-enum to make sure
all the cases are handled and none is duplicated or outside of the
valid values of the enumeration:
void foo (ios::iostate s) {
switch (s) {
case badbit:
case eofbit:
case failbit:
case goodbit:
case __INT_MAX__:
case ~__INT_MAX__: ;
}
}
I thought this was a great idea at first ... but -Wswitch-enum will
complain that the end, min and max enumerators are not handled (even
though __INT_MAX__ and ~__INT_MAX__ have the same values as the max
and min ones, respectively).
Hmm, I didn't see any warnings for the small test case I wrote and
still don't. Just out of curiosity, what did I miss?
enum iostate {
goodbit = 0,
eofbit,
failbit,
badbit,
max = __INT_MAX__,
min = ~__INT_MAX__
};
void foo (iostate s) {
switch (s) {
case badbit:
case eofbit:
case failbit:
case goodbit:
case __INT_MAX__:
case ~__INT_MAX__: ;
;
}
}
I must have messed up my test, I agree this is warning clean.
So I could add tests for those minimum and maximum values, and also
static_assert that the enumerations have an underlying type with the
same representation as int (because if it's actually bigger than int
the operator~ could still produce values outside the range of valid
values).
