Re: [Gm2] M2LexBuf.mod problem with CurrentTokNo and ListOfTokens.LastBucketOffset

[Gaius Mulley]

Scott Robinson <address@hidden> writes:

> Hi Gaius,
> 
> I think there is a problem in M2LexBuf.mod with CurrentTokNo and
> ListOfTokens.LastBucketOffset.  These are both declared as CARDINALs
> and at lines 491 and 493 in procedure GetToken, you are subtracting
> ListOfTokens.LastBucketOffset from CurrentTokNo implying that
> CurrentTokNo is supposed to be strictly greater than or equal to
> ListOfTokens.LastBucketOffset (otherwise you'd get a very large
> CARDINAL value).  At line 811 in procedure AddTokToList, you increment
> ListOfTokens.LastBucketOffset by MaxBucketSize but don't do anything
> with CurrentTokNo.  This evidently can lead to CurrentTokNo being less
> than ListOfTokens.LastBucketOffset which, in the scenario I stumbled
> on, caused GetToken() to recurse enough to segmentation fault due to
> stack exhaustion.

Hi Scott,

interesting - I've now added an assert to 491:

      Assert(CurrentTokNo>=ListOfTokens.LastBucketOffset) ;

Do you have some test code which causes the compiler to fall over?

> By the way, thanks for the quick fixes on the "preprocessor" problem
> and the "returning a string constant" problem.  Those are both working
> fine now.

no problem - I've modified it slightly today to preserve the constant
for a little longer in the hope that better code will be generated.
I will check it in soon..

regards,
Gaius