581473 - possible uninitialized variable use in XPCConvert::JSData2Native

Status: RESOLVED FIXED

(Core :: XPConnect, defect)

Description

[Josh Matthews [:jdm]]

js/src/xpconnect/src/xpcconvert.cpp: In static member function ‘static JSBool XPCConvert::JSData2Native(XPCCallContext&, void*, jsval, const nsXPTType&, JSBool, const nsID*, nsresult*)':
js/src/xpconnect/src/xpcconvert.cpp:683: warning: ‘chars’ may be used uninitialized in this function
js/src/xpconnect/src/xpcconvert.cpp:686: warning: ‘length’ may be used uninitialized in this function

Comment 1

[Boris Zbarsky [:bzbarsky]]

This is your typical "gcc's flow analysis is broken" warning.  The code that looks like this:

  if (JSVAL_IS_VOID(s)) {
    ...
  } else if (!JSVAL_IS_NULL(s)) {
  }

initializes length and chars in all cases except JSVAL_IS_NULL(s).  Then below that the codepaths that use str and chars are guarded so that we don't take them when JSVAL_IS_NULL(s).

Is there any way to silence this warning for known-good code?

Comment 2

[Atul Aggarwal]

Attachment: Patch v1 to fix warning

Please note I could not test this patch.

Comment 3

[Blake Kaplan (:mrbkap) (inactive)]

Comment on attachment 557279 [details] [diff] [review]
Patch v1 to fix warning

Since we should never use this value, I'd prefer to initialize chars to nsnull here so we'll crash if we accidentally do use it. I'll r+ a patch with that change.

Comment 4

[Atul Aggarwal]

Attachment: Patch v2

Change suggested by reviewer.

Comment 5

[Daniel Holbert [:dholbert]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/9b6d23e07968

Comment 6

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/9b6d23e07968