Add placeholder tokens to support pasting with empty arguments.

Along with a passing test to verify that this works.

diff --git a/glcpp-parse.y b/glcpp-parse.y
index 3e0a96528b4a6a92371839cf122ef7a8feb2cd0e..d587a4bf338fb03c62ee1384b1b25513b6edd344 100644 (file)
--- a/glcpp-parse.y
+++ b/glcpp-parse.y
@@ -132,7 +132,7 @@ 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 COMMA_FINAL 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 COMMA_FINAL 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 PLACEHOLDER SPACE
 %token PASTE
 %type <ival> expression INTEGER operator SPACE
 %type <str> IDENTIFIER OTHER
@@ -746,6 +746,9 @@ _token_print (token_t *token)
        case COMMA_FINAL:
                printf (",");
                break;
+       case PLACEHOLDER:
+               /* Nothing to print. */
+               break;
        default:
                fprintf (stderr, "Error: Don't know how to print token type %d\n", token->type);
                break;
@@ -756,6 +759,17 @@ _token_print (token_t *token)
 static void
 _token_paste (token_t *token, token_t *other)
 {
+       /* Pasting a placeholder onto anything makes no change. */
+       if (other->type == PLACEHOLDER)
+               return;
+
+       /* When 'token' is a placeholder, just return contents of 'other'. */
+       if (token->type == PLACEHOLDER) {
+               token->type = other->type;
+               token->value = other->value;
+               return;
+       }
+
        /* A very few single-character punctuators can be combined
         * with another to form a multi-character punctuator. */
        switch (token->type) {
@@ -1159,10 +1173,20 @@ _expand_function_onto (glcpp_parser_t *parser,
                        argument = _argument_list_member_at (arguments,
                                                             parameter_index);
                        /* Before substituting, we expand the argument
-                        * tokens. */
-                       _glcpp_parser_expand_token_list_onto (parser,
-                                                             argument,
-                                                             substituted);
+                        * tokens, or append a placeholder token for
+                        * an empty argument. */
+                       if (argument->head) {
+                               _glcpp_parser_expand_token_list_onto (parser,
+                                                                     argument,
+                                                                     substituted);
+                       } else {
+                               token_t *new_token;
+
+                               new_token = _token_create_ival (substituted,
+                                                               PLACEHOLDER,
+                                                               PLACEHOLDER);
+                               _token_list_append (substituted, new_token);
+                       }
                } else {
                        _token_list_append (substituted, node->token);
                }
@@ -1196,7 +1220,7 @@ _expand_function_onto (glcpp_parser_t *parser,
 
                if (next_non_space == NULL) {
                        fprintf (stderr, "Error: '##' cannot appear at either end of a macro expansion\n");
-                       exit (1);
+                       return FUNCTION_STATUS_SUCCESS;
                }
 
                _token_paste (node->token, next_non_space->token);

diff --git a/tests/058-token-pasting-empty-arguments.c b/tests/058-token-pasting-empty-arguments.c
new file mode 100644 (file)
index 0000000..8ac260c
--- /dev/null
+++ b/tests/058-token-pasting-empty-arguments.c
@@ -0,0 +1,5 @@
+#define paste(x,y) x ## y
+paste(a,b)
+paste(a,)
+paste(,b)
+paste(,)