Weird C code in Bison (yyerror)

Question

I'm using Bison to create a simple parser and have some trouble understanding the C code below. To me it doesn't look like a valid statement, but gcc comepiles it neatly and the code in the block executes on parsing error.

I'd really like to know what this actually means.

The code I refer to is from http://dinosaur.compilertools.net/bison/bison_7.html#SEC66 :

yyerror (s) 
     char *s;
{
  // Some code here
}

score 8 · Accepted Answer · answered Dec 06 '11 at 15:07

8

That's K&R C

In modern C (C89/90 or C99) that would be:

int yyerror(char *s)
{
}

answered Dec 06 '11 at 15:07

Šimon Tóth

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Wow, seems like we (the younger generation) don't know our roots. :) – rickythefox Dec 06 '11 at 15:19
@rickythefox Actually I'm 28 :-) – Šimon Tóth Dec 06 '11 at 15:21

score 4 · Answer 2 · answered Dec 06 '11 at 15:08

4

It means

int yyerror(char* s){
  //some code here
}

code attached to your question is just another way of specifying function argument types.

answered Dec 06 '11 at 15:08

KCH

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score 3 · Answer 3 · answered Dec 06 '11 at 15:10

3

This is old K&R C.

answered Dec 06 '11 at 15:10

Some programmer dude

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score 1 · Answer 4 · answered Dec 06 '11 at 15:11

1

GNU bison is now at version 2.5, see here. Why do you use such an ancient version (you refer to bison 1.25 from 1996)?

The yyerror function is for error recovery. A simple example is here

answered Dec 06 '11 at 15:11

Basile Starynkevitch

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Weird C code in Bison (yyerror)

4 Answers4