Implement (and test) support for macro expansion within conditional expressions.

To do this we have split the existing "HASH_IF expression" into two
productions:

First is HASH_IF pp_tokens which simply constructs a list of tokens.

Then, with that resulting token list, we first evaluate all DEFINED
operator tokens, then expand all macros, and finally start lexing from
the resulting token list. This brings us to the second production,
IF_EXPANDED expression

This final production works just like our previous "HASH_IF
expression", evaluating a constant integer expression.

The new test (54) added for this case now passes.

glcpp-parse.y

@@ -96,6 +96,10 @@ _token_list_append (token_list_t *list, token_t *token);
 static void
 _token_list_append_list (token_list_t *list, token_list_t *tail);
 
+static void
+_glcpp_parser_evaluate_defined (glcpp_parser_t *parser,
+				token_list_t *list);
+
 static void
 _glcpp_parser_print_expanded_token_list (glcpp_parser_t *parser,
 					 token_list_t *list);
@@ -120,14 +124,17 @@ _glcpp_parser_skip_stack_pop (glcpp_parser_t *parser);
 static int
 glcpp_parser_lex (glcpp_parser_t *parser);
 
+static void
+glcpp_parser_lex_from (glcpp_parser_t *parser, token_list_t *list);
+
 %}
 
 %parse-param {glcpp_parser_t *parser}
 %lex-param {glcpp_parser_t *parser}
 
-%token DEFINED HASH HASH_DEFINE_FUNC HASH_DEFINE_OBJ HASH_ELIF HASH_ELSE HASH_ENDIF HASH_IF HASH_IFDEF HASH_IFNDEF HASH_UNDEF IDENTIFIER INTEGER NEWLINE OTHER SPACE
+%token DEFINED ELIF_EXPANDED HASH HASH_DEFINE_FUNC HASH_DEFINE_OBJ HASH_ELIF HASH_ELSE HASH_ENDIF HASH_IF HASH_IFDEF HASH_IFNDEF HASH_UNDEF IDENTIFIER IF_EXPANDED INTEGER NEWLINE OTHER SPACE
 %token PASTE
-%type <ival> expression INTEGER punctuator SPACE
+%type <ival> expression INTEGER operator SPACE
 %type <str> IDENTIFIER OTHER
 %type <string_list> identifier_list
 %type <token> preprocessing_token
@@ -148,28 +155,39 @@ glcpp_parser_lex (glcpp_parser_t *parser);
 
 input:
 	/* empty */
-|	input line {
+|	input line
+;
+
+line:
+	control_line {
 		if (parser->skip_stack == NULL ||
 		    parser->skip_stack->type == SKIP_NO_SKIP)
 		{
 			printf ("\n");
 		}
 	}
-;
-
-line:
-	control_line
 |	text_line {
 		if (parser->skip_stack == NULL ||
 		    parser->skip_stack->type == SKIP_NO_SKIP)
 		{
 			_glcpp_parser_print_expanded_token_list (parser, $1);
+			printf ("\n");
 		}
 		talloc_free ($1);
 	}
+|	expanded_line
 |	HASH non_directive
 ;
 
+expanded_line:
+	IF_EXPANDED expression NEWLINE {
+		_glcpp_parser_skip_stack_push_if (parser, $2);
+	}
+|	ELIF_EXPANDED expression NEWLINE {
+		_glcpp_parser_skip_stack_change_if (parser, "elif", $2);
+	}
+;
+
 control_line:
 	HASH_DEFINE_OBJ	IDENTIFIER replacement_list NEWLINE {
 		_define_object_macro (parser, $2, $3);
@@ -191,8 +209,17 @@ control_line:
 		}
 		talloc_free ($2);
 	}
-|	HASH_IF expression NEWLINE {
-		_glcpp_parser_skip_stack_push_if (parser, $2);
+|	HASH_IF pp_tokens NEWLINE {
+		token_list_t *expanded;
+		token_t *token;
+
+		expanded = _token_list_create (parser);
+		token = _token_create_ival (parser, IF_EXPANDED, IF_EXPANDED);
+		_token_list_append (expanded, token);
+		talloc_unlink (parser, token);
+		_glcpp_parser_evaluate_defined (parser, $2);
+		_glcpp_parser_expand_token_list_onto (parser, $2, expanded);
+		glcpp_parser_lex_from (parser, expanded);
 	}
 |	HASH_IFDEF IDENTIFIER NEWLINE {
 		string_list_t *macro = hash_table_find (parser->defines, $2);
@@ -204,8 +231,17 @@ control_line:
 		talloc_free ($2);
 		_glcpp_parser_skip_stack_push_if (parser, macro == NULL);
 	}
-|	HASH_ELIF expression NEWLINE {
-		_glcpp_parser_skip_stack_change_if (parser, "#elif", $2);
+|	HASH_ELIF pp_tokens NEWLINE {
+		token_list_t *expanded;
+		token_t *token;
+
+		expanded = _token_list_create (parser);
+		token = _token_create_ival (parser, ELIF_EXPANDED, ELIF_EXPANDED);
+		_token_list_append (expanded, token);
+		talloc_unlink (parser, token);
+		_glcpp_parser_evaluate_defined (parser, $2);
+		_glcpp_parser_expand_token_list_onto (parser, $2, expanded);
+		glcpp_parser_lex_from (parser, expanded);
 	}
 |	HASH_ELSE NEWLINE {
 		_glcpp_parser_skip_stack_change_if (parser, "else", 1);
@@ -286,14 +322,6 @@ expression:
 |	'+' expression %prec UNARY {
 		$$ = + $2;
 	}
-|	DEFINED IDENTIFIER %prec UNARY {
-		string_list_t *macro = hash_table_find (parser->defines, $2);
-		talloc_free ($2);
-		if (macro)
-			$$ = 1;
-		else
-			$$ = 0;
-	}
 |	'(' expression ')' {
 		$$ = $2;
 	}
@@ -347,7 +375,7 @@ preprocessing_token:
 |	INTEGER {
 		$$ = _token_create_ival (parser, INTEGER, $1);
 	}
-|	punctuator {
+|	operator {
 		$$ = _token_create_ival (parser, $1, $1);
 	}
 |	OTHER {
@@ -358,7 +386,7 @@ preprocessing_token:
 	}
 ;
 
-punctuator:
+operator:
 	'['			{ $$ = '['; }
 |	']'			{ $$ = ']'; }
 |	'('			{ $$ = '('; }
@@ -389,6 +417,7 @@ punctuator:
 |	';'			{ $$ = ';'; }
 |	','			{ $$ = ','; }
 |	PASTE			{ $$ = PASTE; }
+|	DEFINED			{ $$ = DEFINED; }
 ;
 
 %%
@@ -830,6 +859,9 @@ glcpp_parser_create (void)
 
 	parser->skip_stack = NULL;
 
+	parser->lex_from_list = NULL;
+	parser->lex_from_node = NULL;
+
 	return parser;
 }
 
@@ -849,6 +881,39 @@ glcpp_parser_destroy (glcpp_parser_t *parser)
 	talloc_free (parser);
 }
 
+/* Replace any occurences of DEFINED tokens in 'list' with either a
+ * '0' or '1' INTEGER token depending on whether the next token in the
+ * list is defined or not. */
+static void
+_glcpp_parser_evaluate_defined (glcpp_parser_t *parser,
+				token_list_t *list)
+{
+	token_node_t *node, *next;
+	string_list_t *macro;
+
+	if (list == NULL)
+		return;
+
+	for (node = list->head; node; node = node->next) {
+		if (node->token->type != DEFINED)
+			continue;
+		next = node->next;
+		while (next && next->token->type == SPACE)
+			next = next->next;
+		if (next == NULL || next->token->type != IDENTIFIER) {
+			fprintf (stderr, "Error: operator \"defined\" requires an identifier\n");
+			exit (1);
+		}
+		macro = hash_table_find (parser->defines,
+					 next->token->value.str);
+
+		node->token->type = INTEGER;
+		node->token->value.ival = (macro != NULL);
+		node->next = next->next;
+	}
+}
+	
+
 /* Appends onto 'expansion' a non-macro token or the expansion of an
  * object-like macro.
  *
@@ -1206,7 +1271,53 @@ _define_function_macro (glcpp_parser_t *parser,
 static int
 glcpp_parser_lex (glcpp_parser_t *parser)
 {
-	return glcpp_lex (parser->scanner);
+	token_node_t *node;
+	int ret;
+
+	if (parser->lex_from_list == NULL)
+		return glcpp_lex (parser->scanner);
+
+	node = parser->lex_from_node;
+
+	if (node == NULL) {
+		talloc_free (parser->lex_from_list);
+		parser->lex_from_list = NULL;
+		return NEWLINE;
+	}
+
+	yylval = node->token->value;
+	ret = node->token->type;
+
+	parser->lex_from_node = node->next;
+
+	return ret;
+}
+
+static void
+glcpp_parser_lex_from (glcpp_parser_t *parser, token_list_t *list)
+{
+	token_node_t *node;
+
+	assert (parser->lex_from_list == NULL);
+
+	/* Copy list, eliminating any space tokens. */
+	parser->lex_from_list = _token_list_create (parser);
+
+	for (node = list->head; node; node = node->next) {
+		if (node->token->type == SPACE)
+			continue;
+		_token_list_append (parser->lex_from_list, node->token);
+	}
+
+	talloc_free (list);
+
+	parser->lex_from_node = parser->lex_from_list->head;
+
+	/* It's possible the list consisted of nothing but whitespace. */
+	if (parser->lex_from_node == NULL) {
+		talloc_free (parser->lex_from_list);
+		parser->lex_from_list = NULL;
+	}
 }
 
 static void

glcpp.h

@@ -129,6 +129,8 @@ struct glcpp_parser {
 	string_list_t *active;
 	int space_tokens;
 	skip_node_t *skip_stack;
+	token_list_t *lex_from_list;
+	token_node_t *lex_from_node;
 };
 
 glcpp_parser_t *

tests/054-if-with-macros.c

@@ -0,0 +1,34 @@
+#define one 1
+#define two 2
+#define three 3
+#define five 5
+#if five < two
+failure_1
+#else
+success_1
+#endif
+#if three >= two
+success_2
+#else
+failure_2
+#endif
+#if two + three <= five
+success_3
+#else
+failure_3
+#endif
+#if five - two == three
+success_4
+#else
+failure_4
+#endif
+#if one > three
+failure_5
+#else
+success_5
+#endif
+#if one != five
+success_6
+#else
+failure_6
+#endif