For *ToFixed, in debug mode, assert that the value is in range.

src/core/SkScan.h

 /*
  * Copyright 2011 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkScan_DEFINED
 #define SkScan_DEFINED
@@ skipping 75 matching lines @@
     exceed 32K
 */
 static inline void XRect_set(SkXRect* xr, const SkIRect& src) {
     xr->fLeft = SkIntToFixed(src.fLeft);
     xr->fTop = SkIntToFixed(src.fTop);
     xr->fRight = SkIntToFixed(src.fRight);
     xr->fBottom = SkIntToFixed(src.fBottom);
 }
 
 /** Assign an SkXRect from a SkRect, by promoting the src rect's coordinates
-    from SkScalar to SkFixed. Does not check for overflow if the src coordinates
+    from SkScalar to SkFixed. Behavior is undefined if the src coordinates
     exceed 32K
 */
 static inline void XRect_set(SkXRect* xr, const SkRect& src) {
     xr->fLeft = SkScalarToFixed(src.fLeft);
     xr->fTop = SkScalarToFixed(src.fTop);
     xr->fRight = SkScalarToFixed(src.fRight);
     xr->fBottom = SkScalarToFixed(src.fBottom);
 }
 
 /** Round the SkXRect coordinates, and store the result in the SkIRect.
 */
 static inline void XRect_round(const SkXRect& xr, SkIRect* dst) {
     dst->fLeft = SkFixedRoundToInt(xr.fLeft);
     dst->fTop = SkFixedRoundToInt(xr.fTop);
     dst->fRight = SkFixedRoundToInt(xr.fRight);
     dst->fBottom = SkFixedRoundToInt(xr.fBottom);
 }
 
 /** Round the SkXRect coordinates out (i.e. use floor for left/top, and ceiling
     for right/bottom), and store the result in the SkIRect.
 */
 static inline void XRect_roundOut(const SkXRect& xr, SkIRect* dst) {
     dst->fLeft = SkFixedFloorToInt(xr.fLeft);
     dst->fTop = SkFixedFloorToInt(xr.fTop);
     dst->fRight = SkFixedCeilToInt(xr.fRight);
     dst->fBottom = SkFixedCeilToInt(xr.fBottom);
 }
 
 #endif