X-Git-Url: https://git.draconx.ca/gitweb/cdecl99.git/blobdiff_plain/f522ffe295db90f2072c70ae3583a5f0d064677d..a2c3dad92b2bf55488174c203563224880380c9b:/src/parse-decl.c

diff --git a/src/parse-decl.c b/src/parse-decl.c
index 0f66029..8f0bd38 100644
--- a/src/parse-decl.c
+++ b/src/parse-decl.c
@@ -27,6 +27,33 @@
 #include "scan.h"
 #include "errmsg.h"
 
+/*
+ * Allocate a "parse item", which is a union of several parse tree
+ * structure types, together with a string buffer.  The s_sz argument
+ * specifies the size of the string (including its terminator), which
+ * may be zero.
+ *
+ * The union's declarator member is pre-initialized to a valid "identifier"
+ * declarator, which shares several interesting offsets with the "declspec"
+ * structure for an "identifier" type specifier.
+ */
+struct parse_item *cdecl__alloc_item(size_t s_sz)
+{
+	struct parse_item *ret;
+
+	ret = malloc(offsetof(struct parse_item, s) + s_sz);
+	if (!ret) {
+		cdecl__errmsg(CDECL__ENOMEM);
+		return NULL;
+	}
+
+	ret->u.declarator.child   = NULL;
+	ret->u.declarator.type    = CDECL_DECL_IDENT;
+	ret->u.declarator.u.ident = ret->s;
+
+	return ret;
+}
+
 /*
  * We can represent type specifiers as a bitmap, which gives us a finite
  * list of acceptable bitmap values according to the C standard.  However,
@@ -46,9 +73,10 @@
  */
 static int valid_typespec(struct cdecl_declspec *s)
 {
+	struct cdecl_declspec *c;
 	unsigned long map = 0;
 
-	for (struct cdecl_declspec *c = s; c; c = c->next) {
+	for (c = s; c; c = c->next) {
 		unsigned long bit;
 
 		if (cdecl_spec_kind(c) != CDECL_SPEC_TYPE)
@@ -90,7 +118,7 @@ static int valid_typespec(struct cdecl_declspec *s)
  */
 static bool valid_declspecs(struct cdecl *decl, bool top)
 {
-	struct cdecl_declspec *specs = decl->specifiers;
+	struct cdecl_declspec *c, *specs = decl->specifiers;
 	struct cdecl_declarator *d   = decl->declarators;
 	bool abstract = cdecl_is_abstract(d);
 	unsigned num_storage = 0;
@@ -98,7 +126,7 @@ static bool valid_declspecs(struct cdecl *decl, bool top)
 	if (!valid_typespec(specs))
 		return false;
 
-	for (struct cdecl_declspec *c = specs; c; c = c->next) {
+	for (c = specs; c; c = c->next) {
 		switch (cdecl_spec_kind(c)) {
 		case CDECL_SPEC_TYPE:
 			if (c->type == CDECL_TYPE_VOID &&
@@ -173,22 +201,29 @@ static bool valid_declspecs(struct cdecl *decl, bool top)
 
 static struct cdecl_declarator *reduce_function(struct cdecl *param)
 {
-	struct cdecl_declspec   *spec = param->specifiers;
-	struct cdecl_declarator *decl = param->declarators;
-	struct cdecl_declarator *last;
+	struct cdecl_declarator *d, **p = &param->declarators;
+	struct parse_item *spec = (void *)param->specifiers;
 
-	for (last = decl; last && last->type != CDECL_DECL_NULL;)
-		last = last->child;
+	while ((d = *p)->child)
+		p = &d->child;
 
-	if (!last)
+	if (d->type != CDECL_DECL_NULL)
 		return NULL;
 
-	last->type = CDECL_DECL_IDENT;
-	last->u.ident = spec->ident;
-	free(param);
-	free(spec);
+	/*
+	 * The child and u.ident members of cdecl_declarator are expected
+	 * to be located at identical offsets as, respectively, the next
+	 * and ident members within cdecl_declspec, so the expectation is
+	 * that the compiler can elide both assignments.
+	 */
+	spec->u.declarator.child = (void *)spec->u.declspec.next;
+	spec->u.declarator.u.ident = spec->u.declspec.ident;
+	spec->u.declarator.type = CDECL_DECL_IDENT;
+	*p = &spec->u.declarator;
 
-	return decl;
+	d = param->declarators;
+	free(param);
+	return d;
 }
 
 static bool function_is_reducible(struct cdecl_declarator *d)
@@ -227,204 +262,200 @@ simplify_functions(struct cdecl_declarator **p, struct cdecl_declarator *d)
 	if (!new)
 		return 0; /* e.g. int (foo bar) */
 	*p = new;
-	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).
  *
- * 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).
+ * There are two cases:
  *
- * 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.
+ *   - 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.
+ *
+ *   - 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 int
-reduce_parentheses(struct cdecl_declarator **p, struct cdecl_declarator *d)
+static struct cdecl *fake_function_param(struct cdecl_declarator *d)
 {
 	struct cdecl *param;
 
 	if (d->type != CDECL_DECL_FUNCTION)
-		return 0;
+		return NULL;
 
 	param = d->u.function.parameters;
-	if (param && param->specifiers == NULL) {
-		struct cdecl_declarator *decl;
+	if (!param || param->specifiers)
+		return NULL;
 
-		assert(!param->next);
+	assert(!param->next);
+	return param;
+}
 
-		decl = param->declarators;
-		if (decl->type == CDECL_DECL_NULL) {
-			free(decl);
-			free(param);
-			d->u.function.parameters = NULL;
-			return 0;
-		}
+static int
+reduce_parentheses(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+	struct cdecl *param;
 
-		if (d->child->type != CDECL_DECL_NULL) {
-			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;
 
-		free(d->child);
-		free(param);
-		free(d);
-		*p = decl;
+			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;
+				}
 
-		/*
-		 * We may have replaced d with another fake function which
-		 * also needs to be eliminated.
-		 */
-		if (reduce_parentheses(p, decl) < 0)
-			return -1;
+				param->declarators = d;
+				*p = d = decl;
+			}
 
-		/*
-		 * If the remaining declarator is a function, make sure it's
-		 * valid by checking its reducibility.
-		 */
-		decl = *p;
-		if (decl->type == CDECL_DECL_FUNCTION
-		    && decl->child->type == CDECL_DECL_NULL
-		    && !function_is_reducible(decl)) {
-			cdecl__errmsg(CDECL__EMANYPAREN);
-			return -1;
+			cdecl__free(param);
 		}
-
-		return 0;
-	}
+	} while (simplify_functions(p, d));
 
 	return 0;
 }
 
 /*
- * Function parameters and return types have a few restrictions that are
- * really easy to check in comparison to the above absurdity.
+ * Returns nonzero iff the given specifier list contains a specifier
+ * of the indicated type.
  */
-static int
-check_parameters(struct cdecl_declarator **p, struct cdecl_declarator *d)
+static int have_specifier(struct cdecl_declspec *s, unsigned type)
 {
-	struct cdecl_declspec *spec;
-	struct cdecl *param;
-
-	if (d->type != CDECL_DECL_FUNCTION)
-		return 0;
-
-	for (param = d->u.function.parameters; param; param = param->next) {
-		if (!valid_declspecs(param, false))
-			return -1;
-
-		/* Check for "void" function parameters as a special case. */
-		for (spec = param->specifiers; spec; spec = spec->next) {
-			if (param->declarators->type != CDECL_DECL_NULL)
-				continue;
-			if (spec->type != CDECL_TYPE_VOID)
-				continue;
-
-			if (spec != param->specifiers || spec->next != NULL) {
-				cdecl__errmsg(CDECL__EVOIDPARAM);
-				return -1;
-			} else if (d->u.function.parameters->next) {
-				cdecl__errmsg(CDECL__EVOIDPARAM);
-				return -1;
-			} else if (d->u.function.variadic) {
-				cdecl__errmsg(CDECL__EVOIDPARAM);
-				return -1;
-			}
-		}
-	}
-
+	for (; s; s = s->next)
+		if (s->type == type)
+			return 1;
 	return 0;
 }
 
 /*
- * Functions cannot return arrays or functions.  Since the parse tree is
- * "inside-out", we need to look for functions as the child declarator.
+ * Check syntax restrictions on a function declarator's child declarator.
+ * That is, "pointer to function", "array of function" and "function
+ * returning function".
+ *
+ * Returns -1 if the declaration is invalid, or 0 otherwise.
  */
-static int
-check_rettypes(struct cdecl_declarator **p, struct cdecl_declarator *d)
+static int check_function_child(struct cdecl_declarator *d)
 {
-	if (!d->child || d->child->type != CDECL_DECL_FUNCTION)
-		return 0;
+	struct cdecl_pointer *ptr;
 
 	switch (d->type) {
+	case CDECL_DECL_POINTER:
+		ptr = &d->u.pointer;
+		if (have_specifier(ptr->qualifiers, CDECL_QUAL_RESTRICT)) {
+			/* pointer to function cannot be restrict qualified. */
+			cdecl__errmsg(CDECL__ERESTRICTFUNC);
+			return -1;
+		}
+		return 0;
 	case CDECL_DECL_FUNCTION:
+		/* function returning function is never allowed. */
 		cdecl__errmsg(CDECL__ERETFUNC);
 		return -1;
 	case CDECL_DECL_ARRAY:
-		cdecl__errmsg(CDECL__ERETARRAY);
+		/* array of function is never allowed. */
+		cdecl__errmsg(CDECL__EFUNCARRAY);
 		return -1;
 	}
 
 	return 0;
 }
 
-static int
-check_arrays(struct cdecl_declarator **p, struct cdecl_declarator *d)
+/*
+ * Check a function parameter declaration for validity, which means it has a
+ * valid combination of declaration specifiers and, if it is a void parameter,
+ * that it is the one special case where this is allowed.
+ *
+ * Returns -1 if the declaration is invalid, or 0 otherwise.
+ */
+static int check_function_param(struct cdecl_function *f, struct cdecl *param)
 {
-	if (!d->child || d->child->type != CDECL_DECL_ARRAY)
-		return 0;
-
-	switch (d->type) {
-	case CDECL_DECL_FUNCTION:
-		cdecl__errmsg(CDECL__EFUNCARRAY);
+	if (!valid_declspecs(param, false))
 		return -1;
+
+	/* Check for "void" function parameters as a special case. */
+	if (param->declarators->type == CDECL_DECL_NULL
+	    && have_specifier(param->specifiers, CDECL_TYPE_VOID))
+	{
+		struct cdecl *fp = f->parameters;
+
+		if (f->variadic || fp->next || fp->specifiers->next) {
+			cdecl__errmsg(CDECL__EVOIDPARAM);
+			return -1;
+		}
 	}
 
 	return 0;
 }
 
-static int
-normalize_specs(struct cdecl_declarator **p, struct cdecl_declarator *d)
+/*
+ * Normalize the specifier lists for function parameters, and then check the
+ * function declarator for validity.
+ *
+ * Returns -1 if the declaration is invalid, or 0 otherwise.
+ */
+static int postproc_function(struct cdecl_declarator *d)
 {
-	struct cdecl_function *func;
-	struct cdecl_pointer *ptr;
+	struct cdecl_function *func = &d->u.function;
+	struct cdecl *param;
+	int rc;
 
-	switch (d->type) {
-	case CDECL_DECL_POINTER:
-		ptr = &d->u.pointer;
-		ptr->qualifiers = cdecl__normalize_specs(ptr->qualifiers);
-		break;
-	case CDECL_DECL_FUNCTION:
-		func = &d->u.function;
-		for (struct cdecl *i = func->parameters; i; i = i->next)
-			i->specifiers = cdecl__normalize_specs(i->specifiers);
-		break;
+	for (param = func->parameters; param; param = param->next) {
+		param->specifiers = cdecl__normalize_specs(param->specifiers);
+
+		if ((rc = check_function_param(func, param)) < 0)
+			return rc;
 	}
 
-	return 0;
+	return check_function_child(d->child);
 }
 
 static int
-check_qualifiers(struct cdecl_declarator **p, struct cdecl_declarator *d)
+postproc_common(struct cdecl_declarator **p, struct cdecl_declarator *d)
 {
-	struct cdecl_declspec *spec;
 	struct cdecl_pointer *ptr;
 
-	if (!d->child || d->child->type != CDECL_DECL_POINTER)
+	switch (d->type) {
+	case CDECL_DECL_POINTER:
+		ptr = &d->u.pointer;
+		ptr->qualifiers = cdecl__normalize_specs(ptr->qualifiers);
 		return 0;
-
-	ptr = &d->child->u.pointer;
-	for (spec = ptr->qualifiers; spec; spec = spec->next) {
-		if (spec->type == CDECL_QUAL_RESTRICT
-		    && d->type == CDECL_DECL_FUNCTION) {
-			cdecl__errmsg(CDECL__ERESTRICTFUNC);
+	case CDECL_DECL_FUNCTION:
+		return postproc_function(d);
+	case CDECL_DECL_ARRAY:
+		if (d->child && d->child->type == CDECL_DECL_FUNCTION) {
+			/* function returning array is never allowed. */
+			cdecl__errmsg(CDECL__ERETARRAY);
 			return -1;
 		}
+		return 0;
 	}
 
 	return 0;
@@ -470,9 +501,9 @@ static int forall_declarators(struct cdecl *decl,
 
 static struct cdecl *do_parse(const char *str, int english_mode)
 {
+	struct cdecl *decl = NULL;
 	YY_BUFFER_STATE state;
 	yyscan_t scanner;
-	struct cdecl *decl;
 
 #if YYDEBUG
 	extern int cdecl__yydebug;
@@ -484,8 +515,15 @@ static struct cdecl *do_parse(const char *str, int english_mode)
 		return NULL;
 
 	state = cdecl__yy_scan_string(str, scanner);
-	if (cdecl__yyparse(scanner, &decl) != 0)
+	if (cdecl__yyparse(scanner, &decl) != 0) {
+		/*
+		 * If the input consists of a complete, valid declaration
+		 * followed by some garbage, that parsed declaration will
+		 * be output by the parser and we need to free it here.
+		 */
+		cdecl__free(decl);
 		decl = NULL;
+	}
 	cdecl__yy_delete_buffer(state, scanner);
 	cdecl__yylex_destroy(scanner);
 
@@ -513,26 +551,16 @@ static int do_postprocess(struct cdecl *decl, int english_mode)
 		if (!english_mode) {
 			if (forall_declarators(i, reduce_parentheses) < 0)
 				return 0;
-			if (forall_declarators(i, simplify_functions) < 0)
-				return 0;
 		}
 
-		if (forall_declarators(i, check_parameters) < 0)
-			return 0;
-		if (forall_declarators(i, check_rettypes) < 0)
-			return 0;
-		if (forall_declarators(i, check_arrays) < 0)
-			return 0;
-		if (forall_declarators(i, normalize_specs) < 0)
-			return 0;
-		if (forall_declarators(i, check_qualifiers) < 0)
+		if (forall_declarators(i, postproc_common) < 0)
 			return 0;
 
 		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;
 		}