A small group of similar bugs was introduced into Parserm.h in
library 6/9. The return values from this routine were changed so
that 0, which used to mean 'failed', now means, "result in
multiple object list." A few spots in ParseToken still return 0,
when they should return the new value for an error condition,
'-1' (minus one). These bugs were seen most often as "vile 0 errors from hell".
They cause Inform to call actions with 'noun' or 'second' set to
0, which assume 'noun' or 'second' will be an object. If you were
using the 'trace' debugging verb, you could see that Inform
thought it had succesfully matched tokens that it had not.
About Patches
Issue L60901
ParseToken() returns wrong value
Submitted by: Neil Cerutti
Appeared in: Library 6/9
Fixed in: Library 6/10
Problem
Solution
--- parserm Wed Apr 28 21:26:18 1999
+++ parserm.h Tue Jun 29 08:53:24 1999
@@ -1619,7 +1619,7 @@
NUMBER_TOKEN:
l=TryNumber(wn++);
- if (l==-1000) { etype=NUMBER_PE; rfalse; }
+ if (l==-1000) { etype=NUMBER_PE; return -1; }
#ifdef DEBUG;
if (parser_trace>=3) print " [Read number as ", l, "]^";
#endif;
@@ -1767,7 +1767,7 @@
for (l=1:l<=LanguageDescriptors-->0:l=l+4)
if (o == LanguageDescriptors-->l) jump AssumeDescriptor;
pronoun__word=pronoun_word; pronoun__obj=pronoun_obj;
- etype=VAGUE_PE; return 0;
+ etype=VAGUE_PE; return -1;
}
}
@@ -1781,7 +1781,7 @@
.TryAgain;
! First, we parse any descriptive words (like "the", "five" or "every"):
- l = Descriptors(token_allows_multiple); if (l~=0) { etype=l; return 0; }
+ l = Descriptors(token_allows_multiple); if (l~=0) { etype=l; return -1; }
.TryAgain2;
@@ -1882,7 +1882,7 @@
if (l==0)
{ if (indef_possambig)
{ ResetDescriptors(); wn = desc_wn; jump TryAgain2; }
- etype=CantSee(); return l; ! Choose best error
+ etype=CantSee(); return -1; ! Choose best error
}
Last updated 2 May 2008. The librarian in charge of this page is Roger Firth. Please email any comments, suggestions or corrections to roger@firthworks.com.