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revision 1.59 by akim, Fri May 3 17:09:50 2002 UTC revision 1.60 by akim, Sat May 4 08:48:04 2002 UTC
# Line 277  Rewrite the reader in Flex/Bison.  There Line 277  Rewrite the reader in Flex/Bison.  There
277  particular, expect the scanner to be hard to write.  Many interesting  particular, expect the scanner to be hard to write.  Many interesting
278  features cannot be implemented without such a new reader.  features cannot be implemented without such a new reader.
279    
 * Problems with aliases  
 From: "Baum, Nathan I" <s0009525@chelt.ac.uk>  
 Subject: Token Alias Bug  
 To: "'bug-bison@gnu.org'" <bug-bison@gnu.org>  
   
 I've noticed a bug in bison. Sadly, our eternally wise sysadmins won't let  
 us use CVS, so I can't find out if it's been fixed already...  
   
 Basically, I made a program (in flex) that went through a .y file looking  
 for "..."-tokens, and then outputed a %token  
 line for it. For single-character ""-tokens, I reasoned, I could just use  
 [%token 'A' "A"]. However, this causes Bison to output a [#define 'A' 65],  
 which cppp chokes on, not unreasonably. (And even if cppp didn't choke, I  
 obviously wouldn't want (char)'A' to be replaced with (int)65 throughout my  
 code.  
   
 Bison normally forgoes outputing a #define for a character token. However,  
 it always outputs an aliased token -- even if the token is an alias for a  
 character token. We don't want that. The problem is in /output.c/, as I  
 recall. When it outputs the token definitions, it checks for a character  
 token, and then checks for an alias token. If the character token check is  
 placed after the alias check, then it works correctly.  
   
 Alias tokens seem to be something of a kludge. What about an [%alias "..."]  
 command...  
   
         %alias T_IF "IF"  
   
 Hmm. I can't help thinking... What about a --generate-lex option that  
 creates an .l file for the alias tokens used... (Or an option to make a  
 gperf file, etc...)  
   
280  * Presentation of the report file  * Presentation of the report file
281  From: "Baum, Nathan I" <s0009525@chelt.ac.uk>  From: "Baum, Nathan I" <s0009525@chelt.ac.uk>
282  Subject: Token Alias Bug  Subject: Token Alias Bug

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