trinity-devel@lists.pearsoncomputing.net

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Month: May 2012

Re: [trinity-devel] Commit c94de3af (GCC 4.7 fix) × KMail

From: "David C. Rankin" <drankinatty@...>
Date: Sat, 26 May 2012 18:03:46 -0500
On 05/26/2012 02:54 AM, Francois Andriot wrote:
> Le 26/05/2012 01:21, David C. Rankin a écrit :
>>
>> OK,
>>
>>    I see how that happened, but I still don't think I could have discerned
>> whether the 'it' at 496 went with the 'it' from 475 or the 'it' from 485 since
>> it is within the code-block for TQMap<TQGuardedPtr<KMFolder>, bool>::Iterator
>> it, but it is _not_ expressly in the code-block for
>> TQMap<TQGuardedPtr<KMFolder>, int>::Iterator unread_it
>>
>>    How would you know which 'it' needed to go to 'unread_it' or 'it' in this
>> case?  When we went over it before, the way was to start with the inner-most
>> 'it' and work out from there to separate code-blocks. That didn't work in this
>> case. Any other tricks?
>>
> 
> 
> Hello,
> in the original code, the "it" is first declared in a "for" statement (line
> 475), then redeclared differently inside this "for" loop. (line 485).
> Inside that loop, any "it" usage BEFORE the redeclaration (line 476 to 484)
> refer the first declaration, and any "it" AFTER the redeclaration (line 486 to
> end of loop) refer to the new declaration. The redeclaration implies that the
> original variable is unreferenced, so it cannot be used anymore.
> 
> So, when you rename the variable of a conflicting redeclaration (this is
> mandatory for GCC 4.7), you must update all references to this variable that
> come AFTER the redeclaration too.
> 
> Francois
> 

Thank you Francios,

  In this case, the 'it' declared at 475 isn't unreferenced until the 475 for
loop ends at line 548. That's what makes this unclear to me. The problem I must
not be explaining correctly is this (starting line 475):

  for ( TQMap<TQGuardedPtr<KMFolder>, bool>::Iterator it = mPendingUpdates.begin();
        it != mPendingUpdates.end(); ++it)
  {

  <snip - next line 485 (originally '::Iterator it') >

  TQMap<TQGuardedPtr<KMFolder>, int>::Iterator unread_it =
      mFoldersWithUnread.find(fldr);

  <snip - next line 496>

    int diff = unread - it.data();

  <snip - next line 548 - closing for>

  }

  Since there are no bounding braces '{}' for the line 485 redeclaration, there
is nothing that specifically limits the scope of the 485 redeclaration. So if in
the code between 485 and 548 there were additional references to 'it.something',
how can you tell whether it is the it from the 475 declaration or the 'it' (now
unread_it) that belongs to 485 redeclaration? What if there was at say line 530
something like:

  KMFolder *prev_fldr_with_unread = it.key() - jump;

  Can you say that just because there was a redeclaration at 485, that the 'it'
at line 530 must be associated with with the redeclaration, even though it is
still within the code-block for the original it?

-- 
David C. Rankin, J.D.,P.E.