[apparmor] [PATCH 06/13] Enable the parser to pass the next token to be returned to the lexer

[John Johansen]

On 02/14/2012 11:14 AM, Kees Cook wrote:
> Hi John,
> 
> On Tue, Feb 14, 2012 at 09:32:28AM -0800, John Johansen wrote:
>> Currently the parser can not directly influence the lexer output.  This
>> limits the grammar and also how the parser can be invoked.  Allow the
>> parser to pass the next TOKEN that the lexer will return.
>>
>> This is has two uses:  It allows us to trick the bison parser into having
>> multiple start symbols, allowing us to say invoke the parser on an
>> individual network or file rule.  It also allows the semantic analysis of
>> the parser to change the language recognized.  This can be leveraged to
>> overcome some of the limitation of bison's LALR parse generator.
>>
>> Signed-off-by: John Johansen <john.johansen at canonical.com>
>> ---
>>  parser/parser.h      |    5 +++++
>>  parser/parser_lex.l  |    9 +++++++++
>>  parser/parser_yacc.y |    3 +++
>>  3 files changed, 17 insertions(+), 0 deletions(-)
>>
>> diff --git a/parser/parser.h b/parser/parser.h
>> index 346620a..7d71fd8 100644
>> --- a/parser/parser.h
>> +++ b/parser/parser.h
>> @@ -25,6 +25,11 @@
>>  #include "libapparmor_re/apparmor_re.h"
>>  #include "libapparmor_re/aare_rules.h"
>>  
>> +/* Global variable to pass token to lexer.  Will be replaced by parameter
>> + * when lexer and parser are made reentrant
>> + */
>> +extern int parser_token;
>> +
>>  typedef enum pattern_t pattern_t;
>>  
>>  struct flagval {
>> diff --git a/parser/parser_lex.l b/parser/parser_lex.l
>> index e4f8f66..87ede55 100644
>> --- a/parser/parser_lex.l
>> +++ b/parser/parser_lex.l
>> @@ -222,6 +222,15 @@ LT_EQUAL	<=
>>  
>>  %%
>>  
>> +%{
>> +/* Copied directly into yylex function */
>> +	if (parser_token) {
>> +		int t = parser_token;
>> +		parser_token = 0;
>> +		return t;
>> +	}
>> +%}
>> +
>>  <INCLUDE>{
>>  	{WS}+	{ /* Eat whitespace */ }
>>  	\<([^\> \t\n]+)\>	{	/* <filename> */
>> diff --git a/parser/parser_yacc.y b/parser/parser_yacc.y
>> index af56a20..2a4fa5d 100644
>> --- a/parser/parser_yacc.y
>> +++ b/parser/parser_yacc.y
>> @@ -69,6 +69,8 @@ struct value_list {
>>  	struct value_list *next;
>>  };
>>  
>> +int parser_token = 0;
>> +
>>  void free_value_list(struct value_list *list);
>>  struct cod_entry *do_file_rule(char *namespace, char *id, int mode,
>>  			       char *link_id, char *nt);
>> @@ -77,6 +79,7 @@ void add_local_entry(struct codomain *cod);
>>  
>>  %}
>>  
>> +
>>  %token TOK_ID
>>  %token TOK_CONDID
>>  %token TOK_CARET
> 
> Needless whitespace addition in this chunk. Otherwise, looks fine to me.
>
yep, and drat another one I didn't catch

thanks

 
> -Kees
>