851556 - GestureEventListener.cpp:140:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]

Status: RESOLVED FIXED

(Core :: Graphics: Layers, defect)

Description

[Daniel Holbert [:dholbert]]

Build warning:
{
/mozilla/gfx/layers/ipc/GestureEventListener.cpp: In member function ‘nsEventStatus mozilla::layers::GestureEventListener::HandleInputEvent(const mozilla::InputData&)’:

/mozilla/gfx/layers/ipc/GestureEventListener.cpp:140:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]

/mozilla/gfx/layers/ipc/GestureEventListener.cpp:142:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
}

This is from these comparisons:
> 140     if (event.mTime - mTapStartTime <= MAX_TAP_TIME) {
> 141       if (mState == GESTURE_WAITING_DOUBLE_TAP &&
> 142           event.mTime - mLastTapEndTime > MAX_TAP_TIME) {
https://mxr.mozilla.org/mozilla-central/source/gfx/layers/ipc/GestureEventListener.cpp#140

"event.mTime" is a uint32_t, and "mTapStartTime" is a uint64_t -- so the left side of the comparisons ends up having type uint64_t.

MAX_TAP_TIME is an int (i.e. it's signed), for some reason. It's only got one usage outside of the two lines quoted above -- it's passed to PostDelayedTask here:
https://mxr.mozilla.org/mozilla-central/source/gfx/layers/ipc/GestureEventListener.cpp#171
and *there* it's used as an int.  We could easily make it an unsigned value, though, and just let PostDelayedTask implicitly convert it to an int.  (It's not anywhere near UINT32_MAX, so unsigned --> signed conversion will do the right thing.)

SO: I think we should just make MAX_TAP_TIME unsigned, possibly "uint32_t" to match event.mTime, so that the comparisons against it won't trigger build warnings.

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: fix v1

Comment 2

[Doug Sherk (:drs) (inactive)]

Comment on attachment 725458 [details] [diff] [review]
fix v1

Review of attachment 725458 [details] [diff] [review]:
-----------------------------------------------------------------

Cool! Thanks for the fix.

Comment 3

[Daniel Holbert [:dholbert]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/ff9313fd56e4

Comment 4

[Joe Drew (not getting mail)]

https://hg.mozilla.org/mozilla-central/rev/ff9313fd56e4