On 04/24/2017 05:25 AM, Richard Biener wrote:
The following makes signed overflow undefined for all (non-)optimization
levels. The intent is to remove -fno-strict-overflow signed overflow
behavior as that is not a sensible option to the user (it ends up
with the worst of both -fwrapv and -fno-wrapv). The implementation
details need to be preserved for the forseeable future to not wreck
UBSAN with either associating (-fwrapv behavior) or optimizing
(-fno-wrapv behavior).
The other choice would be to make -fwrapv the default for -O[01].
A second patch in this series would unify -f[no-]wrapv, -f[no-]trapv
and -f[no-]strict-overflow with a
-fsigned-integer-overflow={undefined,wrapping,trapping[,sanitized]}
option, making conflicts amongst the options explicit (and reduce
the number of flag_ variables). 'sanitized' would essentially map
to todays flag_strict_overflow = 0. There's another sole user
of flag_strict_overflow, POINTER_TYPE_OVERFLOW_UNDEFINED - not sure
what to do about that, apart from exposing it as different flag
alltogether.
Further patches in the series would remove -Wstrict-overflow (and
cleanup VRP for example).
Anyway, most controversical part(?) below.
Any comments on this particular patch (and the overall proposal)?
Cleaning up the options is probably a no-brainer anyways.
Thanks,
Richard.
2017-04-24 Richard Biener <rguent...@suse.de>
* common.opt (fstrict-overflow): Enable by default.
* opts.c (default_options_table): Remove OPT_fstrict_overflow entry.
Presumably when this work is complete -fno-strict-overflow will give
some kind of reasonable error message to the user directing them to the
new option that most likely does what they were looking for?
Jeff
