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Fixed crash caused by NaN values in RCTTouchEvent

React Native uses JSON to marshal the data across the bridge.
And because of this we have to avoid using NaN and INF values in events and other pieces of data that suppose to be transfered to/from JS side.
(We also don't want to introduce additional wrapping/escaping semantics for perfomance reasons.)
So, we have to gate all particular cases where there is a possibility of NaN or INF values, and replace these value with something meaningful for each particular case.
We are using `0` as NaN substitution here because:
 * NaN in touch event is super rare case;
 * Conversion to `0` is fast;
 * `0` is okay value for product code in most cases;
 * In all cases `0` is decent analog to "undefined position on screen" for touch event;
 * Nobody will explicitly handle NaN case in product code, just because it is super rare case and actually indicates that something else went wrong.

Reviewed By: javache

Differential Revision: D4918669

fbshipit-source-id: e95fa29e59dcdc40b57519e307b74c1f293da188
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shergin authored and facebook-github-bot committed Apr 21, 2017
1 parent 13f89f4 commit e7c6a4c038936ed54d153eeca7fa6fdf8cf1f503
Showing with 18 additions and 5 deletions.
  1. +5 −5 React/Base/RCTTouchHandler.m
  2. +3 −0 React/Base/RCTUtils.h
  3. +10 −0 React/Base/RCTUtils.m
@@ -156,17 +156,17 @@ - (void)_updateReactTouchAtIndex:(NSInteger)touchIndex
CGPoint touchViewLocation = [nativeTouch.window convertPoint:windowLocation toView:touchView];
NSMutableDictionary *reactTouch = _reactTouches[touchIndex];
reactTouch[@"pageX"] = @(rootViewLocation.x);
reactTouch[@"pageY"] = @(rootViewLocation.y);
reactTouch[@"locationX"] = @(touchViewLocation.x);
reactTouch[@"locationY"] = @(touchViewLocation.y);
reactTouch[@"pageX"] = @(RCTSanitizeNaNValue(rootViewLocation.x, @"touchEvent.pageX"));
reactTouch[@"pageY"] = @(RCTSanitizeNaNValue(rootViewLocation.y, @"touchEvent.pageY"));
reactTouch[@"locationX"] = @(RCTSanitizeNaNValue(touchViewLocation.x, @"touchEvent.locationX"));
reactTouch[@"locationY"] = @(RCTSanitizeNaNValue(touchViewLocation.y, @"touchEvent.locationY"));
reactTouch[@"timestamp"] = @(nativeTouch.timestamp * 1000); // in ms, for JS
// TODO: force for a 'normal' touch is usually 1.0;
// should we expose a `normalTouchForce` constant somewhere (which would
// have a value of `1.0 / nativeTouch.maximumPossibleForce`)?
if (RCTForceTouchAvailable()) {
reactTouch[@"force"] = @(RCTZeroIfNaN(nativeTouch.force / nativeTouch.maximumPossibleForce));
reactTouch[@"force"] = @(RCTSanitizeNaNValue(nativeTouch.force / nativeTouch.maximumPossibleForce, @"touchEvent.force"));
@@ -101,6 +101,9 @@ RCT_EXTERN NSError *RCTErrorWithMessage(NSString *message);
// Convert NaN or infinite values to zero, as these aren't JSON-safe
RCT_EXTERN double RCTZeroIfNaN(double value);
// Returns `0` and log special warning if value is NaN or INF.
RCT_EXTERN double RCTSanitizeNaNValue(double value, NSString *property);
// Convert data to a Base64-encoded data URL
RCT_EXTERN NSURL *RCTDataURL(NSString *mimeType, NSData *data);
@@ -513,6 +513,16 @@ BOOL RCTForceTouchAvailable(void)
return isnan(value) || isinf(value) ? 0 : value;
double RCTSanitizeNaNValue(double value, NSString *property)
if (!isnan(value) && !isinf(value)) {
return value;
RCTLogWarn(@"The value `%@` equals NaN or INF and will be replaced by `0`.", property);
return 0;
NSURL *RCTDataURL(NSString *mimeType, NSData *data)
return [NSURL URLWithString:

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