Production rules don't have the default action

[Eduardo Madrid]

On Bison's manual:

http://www.gnu.org/software/bison/manual/html_node/Actions.html


It states that

?If you don't specify an action for a rule, Bison supplies a default: $$ = $1


However, the attached grammar does not initialize $$ to $1 on the rule in line 
41:

recursion_1: reduction_by_2 // should have default $$ = $1


The program writes 'Top 0' instead of Top 7.


If the default action is put explicitly { $$ = $1 } then it does.


I detected the problem after arduous debugging of a large grammar that was 
converted from using plain C and distilled to a small example, it seems a 
reduction of 1 symbol works, but not reductions of two or more.


There is no mention in the documentation that I have found of cases in which 
the default action for non-empty rules is not issued.


To replicate: bison vb.y && g++ vb.tab.c

?


Thanks in advance for considering this bug.




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vb.y
Description: vb.y