534156 - Fix "nsSVGUtils.cpp:724: warning: ‘axis’ may be used uninitialized in this function"

Status: RESOLVED FIXED

(Core :: SVG, defect)

Description

[Daniel Holbert [:dholbert]]

Attachment: fix: add "default" case to switch statement

GCC 4.3.3 on Linux gives us this warning, when building mozilla-central:
> /layout/svg/base/src/nsSVGUtils.cpp: In static member function ‘static float nsSVGUtils::ObjectSpace(const gfxRect&, const nsSVGLength2*)’:
> /layout/svg/base/src/nsSVGUtils.cpp:724: warning: ‘axis’ may be used uninitialized in this function

Not all instances of this type of build warning are actually bugs, but this
particular one appears to sort of be, and it's easily fixable.  Relevant snippet of code:

724   float fraction, axis;
725 
726   switch (aLength->GetCtxType()) {
727   case X:
728     axis = aRect.Width();
729     break;
730   case Y:
731     axis = aRect.Height();
732     break;
733   case XY:
734     axis = float(ComputeNormalizedHypotenuse(aRect.Width(), aRect.Height()));
735   }
[...]
743   return fraction * axis;

The function aLength->GetCtxType() returns a PRUint8.  In the (unlikely) event that this value is anything other than the enums X, Y, or XY, then we never set |axis|, and we'll return a completely bogus value from ObjectSpace().

Attached patch trivially fixes this by zeroing |axis| in a new 'default' case of the switch statement, with a NS_NOTREACHED to more explicitly state our assumption that we should never get there.

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: fix: add "default" case to switch statement

I changed "0" to "0.0f" in this version. (since axis is a float)

Comment 2

[Daniel Holbert [:dholbert]]

http://hg.mozilla.org/mozilla-central/rev/c58bb77dbd55