497698 - Can we remove aOther.IsNull() assertion from TimeStamp's operator-

Status: RESOLVED WONTFIX

(Core :: XPCOM, defect)

Description

[Nochum Sossonko [:Natch]]

I don't see what's wrong with subtracting zero? The assertion that the TimeStamp we're subtracting from is not 0 is definitely necessary, but what does it matter if aOther is 0? Patch forthcoming if it's ok'ed.

Comment 1

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Null means "no timestamp" or "don't know". It makes no sense to do anything with Null except maybe compare it to something else.

Comment 2

[Nochum Sossonko [:Natch]]

In the code I'm using it in bug 61098 I want to compare the last time a dialog was opened to TimeStamp::Now. Problem is that it starts with 0 the first time a dialog is opened as there never was a dialog before. So 0 (or Null) to me means "no time yet".

Comment 3

[Nochum Sossonko [:Natch]]

Sorry, not compare, rather subtract. My intention is to see if the last dialog  was opened within 3 seconds of this new dialog.

Comment 4

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Right. So you should write
  if (!mLastOpen.IsNull() && now - mLastOpen < ...) {}

Comment 5

[Nochum Sossonko [:Natch]]

(In reply to comment #4)
> Right. So you should write
>   if (!mLastOpen.IsNull() && now - mLastOpen < ...) {}

I did that after encountering the assertion, but I was trying to understand what the issue was with just subtracting without the null check. Just trying to be lazy, I guess.

->WONTFIX