(Crossposted to DKB List...)


This email is a fix for the 'Infinite
Recursion Macro' bug, reported on the
DKB mail list 11/10/1998.

>I have found what I consider to be a bug
>in POV-Ray 3.1  Accidently causing a
>macro to infinitely recurse causes POV-ray
>to seg-fault.
>
>Here is some pov code which produces the
>problem:
>
>#version 3.1;
>
>#macro F()
>  F()
>#end
>
>F()

I have built a Pov-Ray 3.1 binary for Win32 from
the MSDOS sources distribution.  The reason for
the seg-fault appears reasonably obvious:

1. Check that we havn't allocated too many
   symbol tables.

Add_Sym_Table(char *s) [tokenise.c]
...
  if ((Table_Index++)==MAX_NUMBER_OF_TABLES)
  {
    Error("Too many nested symbol tables");
  }
...

2. Error handler decides the error is fatal,
   and tries to free resources:

void Terminate_Tokenizer() [tokenise.c]
...
  while(Table_Index >= 0)
  {
     Destroy_Table(Table_Index--);
  }
...

The problem is that the table index is
out of range for the first 'Destroy_Table'
call.  The fix is to decrement
Table_Index before handling the error:

Add_Sym_Table(char *s) [tokenise.c]
...
  if ((Table_Index++)==MAX_NUMBER_OF_TABLES)
  {
    Table_Index--;
    Error("Too many nested symbol tables");
  }
...

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