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Barriers

When using the nocombine configuration option, tcc divides the rules into self-contained subsets, which are separated by lines with the word

barrier

When iterating through rules, i.e. when looking for a match, barriers can be ignored. However, they change the meaning of the action unspec: when encountering unspec, the classifier has to look for a barrier following the current rule, and proceed with the next rule following this barrier. Only if there is no barrier following the current rule can the classifier return unspec as the final result.

Example:

Line Action/rule Next rule
    Match No match
1 action 0 = unspec    
2 action 1 = class 1:1    
3 $\ldots$    
4 match ... action 1 return 5
5 match ... action 0 8 6
6 match action 1 return --
7 barrier 8  
8 match ... action 1 return 9
9 match action 0 return --


next up previous contents
Next: Data returned Up: Configuration data format Previous: Rules   Contents
Martin A. Brown 2003-11-06