WONKY

F diff --git a/src/frontend/lex/lex_preprocessing_directive.c b/src/frontend/lex/lex_preprocessing_directive.c
--- a/src/frontend/lex/lex_preprocessing_directive.c
+++ b/src/frontend/lex/lex_preprocessing_directive.c
  		case PKW_DEFINE:
  			return preprocessing_lex_define_directive(lexer_data,token_location);
  		case PKW_UNDEF:
- 			return get_error_token("PREPROCESSING UNDEF NOT DONE",token_location,lexer_data->previous_token_location,lexer_data->program);	
+ 			return preprocessing_lex_undef_directive(lexer_data,token_location);
  		case PKW_LINE:
  			return preprocessing_lex_line_directive(lexer_data,token_location);
  		case PKW_ERROR:
  	
  	return (struct token*)ret;
  }
+ struct token* preprocessing_lex_undef_directive(struct Lexer_Data *lexer_data,struct Source_Location *where)
+ {
+ 	struct token_undef_directive *ret;
+ 	struct token *hold_token;
+ 	ret=wonky_malloc(sizeof(struct token_undef_directive));
+ 	ret->type=PKW_UNDEF;
+ 	ret->delta=get_source_location_delta(lexer_data->previous_token_location,where);
+ 	ret->id=NULL;
+ 
+ 	hold_token=preprocessing_extract_next_token(lexer_data);
+ 
+ 	if(hold_token==NULL || !token_is_identifier_in_preprocessing(hold_token))
+ 	{
+ 		push_lexing_error("Expected id in #undef directive",lexer_data);
+ 	}else
+ 	{
+ 		if(token_is_a_special_macro(hold_token))
+ 		{
+ 			push_lexing_error("Special macro id in #undef directive is not allowed",lexer_data);
+ 		}else
+ 		{
+ 			ret->id=hold_token;
+ 		}
+ 	}
+ 	return (struct token*)ret;
+ }
  void preprocessing_push_tokens_into_queue_until_eol(struct Lexer_Data *lexer_data,struct Queue *queue)
  {
  
F diff --git a/src/semantics/program/translation_unit.c b/src/semantics/program/translation_unit.c
--- a/src/semantics/program/translation_unit.c
+++ b/src/semantics/program/translation_unit.c
  }
  void token_ptr_execute_undef_directive(struct Token_Pointer *ptr,struct token_undef_directive *undef_directive)
  {
+ 	struct identifier *id;
  	token_ptr_goto_next_token(ptr);
+ 	if(undef_directive->id->type==KW_ID)
+ 	{
+ 		id=((struct token_identifier*)undef_directive->id)->id;	
+ 	}else if(token_is_keyword(undef_directive->id))
+ 	{
+ 		id=((struct token_keyword*)undef_directive->id)->id;	
+ 	}else
+ 	{
+ 		wonky_assert(SHOULD_NOT_REACH_HERE);
+ 	}
+ 	if(id!=NULL)
+ 	{
+ 		id->number_of_translation_unit_where_id_was_last_defined_as_a_macro=0;
+ 	}
  }
  void token_ptr_execute_line_directive(struct Token_Pointer *ptr,struct token_line_directive *line_directive)
  {
F diff --git a/src/syntax/token/token.c b/src/syntax/token/token.c
--- a/src/syntax/token/token.c
+++ b/src/syntax/token/token.c
  
  	if(token->type==KW_ID)
  		return id_is_a_macro(((struct token_identifier*)token)->id,macro_expansion_number,translation_unit_number);
+ 	else if(token_is_keyword(token))
+ 		return id_is_a_macro(((struct token_keyword*)token)->id,macro_expansion_number,translation_unit_number);
  	else
  		return token_is_a_special_macro(token) || token_is_keyword(token);
  }
F diff --git a/src/syntax/token/token.h b/src/syntax/token/token.h
--- a/src/syntax/token/token.h
+++ b/src/syntax/token/token.h
  {
  	enum LEXER_TYPE type;
  	struct Source_Location_Delta *delta;
- 	struct identifier *id;
+ 	struct token *id; /*keywords are also identifiers in preprocessing*/
  };
  struct token_line_directive
  {