X-Git-Url: https://git.draconx.ca/gitweb/cdecl99.git/blobdiff_plain/248d73924d6136eee0497a7456aba90bfef633e3..5383a8b913e74ebe5faa39ef3e570afb95779141:/src/parse-decl.c

diff --git a/src/parse-decl.c b/src/parse-decl.c
index 6ab624e..a6204a1 100644
--- a/src/parse-decl.c
+++ b/src/parse-decl.c
@@ -230,30 +230,40 @@ simplify_functions(struct cdecl_declarator **p, struct cdecl_declarator *d)
 	free(d->child);
 	free(d);
 
-	return 0;
+	return 1;
 }
 
 /*
- * The parser's bias towards considering things as functions whenever possible
- * makes nested parentheses tricky.  (x) is considered to be part of a function
- * declarator until simplify_functions converts it.  The problem is that
- * (((x))) is not valid as part of a function declarator, but it *is* valid
- * as an identifier enclosed 3 times in parentheses.  This is complicated by
- * the fact that things like (((int))) are not valid anywhere.
+ * The main parser's bias towards considering things as functions whenever
+ * possible makes nested parentheses tricky.  "(x)" is considered to be part
+ * of a function declarator until simplify_functions converts it.  The problem
+ * is that "(((x)))" is not valid as part of a function declarator, but it _is_
+ * valid as either an identifier enclosed thrice in parentheses, or an abstract
+ * function declarator enclosed twice in parentheses.
+ *
+ * To avoid ambiguities, the main parser actually returns a function declarator
+ * for every pair of parentheses.  The ones we need to look at consist of a
+ * single parameter with an empty specifier list (noting that every real
+ * function parameter will have at least one type specifier).
+ *
+ * There are two cases:
  *
- * To avoid ambiguities, the parser actually emits a "function" declarator for
- * every pair of parentheses.  The ones that can't reasonably be functions
- * consist of a single "parameter" with no declaration specifiers (note that
- * every valid function parameter will have at least one type specifier).
+ *   - For (), the parser emits a parameter with a lone null declarator.
+ *     This fake parameter simply gets deleted, leaving us with a normal
+ *     function declarator with an empty identifier list.
  *
- * This pass is to remove these fake functions from the parse tree.  We take
- * care to avoid turning invalid things like ((int)) into valid things like
- * (int) by observing that the only valid function declarators that appear
- * in these "fake" parentheses are those that have a non-null child declarator
- * (for instance, int ((*)(int)) *or* those that will be eliminated by the
- * simplify_functions pass.
+ *   - Otherwise, the parameter's outermost declarator is not null.  The
+ *     function itself is deleted, replaced in the parse tree with the
+ *     fake parameter's declarator.
+ *
+ * Repeating until there no fake parameters, this reduction transforms, for
+ * example, "(((x)))" into "(x)", an abstract function declarator.  The result
+ * is then subject to the function simplification step, which will turn "(x)"
+ * into x (declaring an identifier).
+ *
+ * The whole process is repeated until no more changes are made to the parse
+ * tree, or a syntax error is detected.
  */
-
 static struct cdecl *fake_function_param(struct cdecl_declarator *d)
 {
 	struct cdecl *param;
@@ -273,34 +283,28 @@ static int
 reduce_parentheses(struct cdecl_declarator **p, struct cdecl_declarator *d)
 {
 	struct cdecl *param;
-	int fake = 0;
-
-	while ((param = fake_function_param(d))) {
-		struct cdecl_declarator *decl = param->declarators;
-		d->u.function.parameters = NULL;
-
-		if (decl->type != CDECL_DECL_NULL) {
-			if (d->child->type != CDECL_DECL_NULL) {
-				/* Found fake parameter on real function. */
-				d->u.function.parameters = param;
-				cdecl__errmsg(CDECL__EBADPARAM);
-				return -1;
+
+	do {
+		d = *p;
+		while ((param = fake_function_param(d))) {
+			struct cdecl_declarator *decl = param->declarators;
+			d->u.function.parameters = NULL;
+
+			if (decl->type != CDECL_DECL_NULL) {
+				if (d->child->type != CDECL_DECL_NULL) {
+					/* Fake parameter on real function. */
+					d->u.function.parameters = param;
+					cdecl__errmsg(CDECL__EBADPARAM);
+					return -1;
+				}
+
+				param->declarators = d;
+				*p = d = decl;
 			}
 
-			param->declarators = d;
-			*p = d = decl;
-			fake = 1;
+			cdecl__free(param);
 		}
-
-		cdecl__free(param);
-	}
-
-	simplify_functions(p, d);
-	if (fake && (*p)->type == CDECL_DECL_FUNCTION) {
-		/* Started with a fake function but ended with a real one. */
-		cdecl__errmsg(CDECL__EMANYPAREN);
-		return -1;
-	}
+	} while (simplify_functions(p, d));
 
 	return 0;
 }
@@ -514,8 +518,8 @@ static int do_postprocess(struct cdecl *decl, int english_mode)
 		if (!valid_declspecs(i, true))
 			return 0;
 
-		if (cdecl_is_abstract(i->declarators)
-		    && (i != decl || i->next)) {
+		if (decl->next && cdecl_is_abstract(i->declarators)) {
+			/* Abstract full declarators: there can only be one. */
 			cdecl__errmsg(CDECL__EDECLTYPE);
 			return 0;
 		}