X-Git-Url: https://git.draconx.ca/gitweb/cdecl99.git/blobdiff_plain/8f66c0f29d726879468762bd65d1062b6939d2ea..425ed781f7a27bc415e13a1901899e2c7b11e4c8:/src/parse-decl.c

diff --git a/src/parse-decl.c b/src/parse-decl.c
index 45ade35..4489532 100644
--- a/src/parse-decl.c
+++ b/src/parse-decl.c
@@ -1,28 +1,73 @@
+/*
+ *  Parse and validate C declarations.
+ *  Copyright © 2011-2012 Nick Bowler
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <config.h>
 #include <stdio.h>
 #include <assert.h>
+#include <stdbool.h>
 
 #include "cdecl.h"
 #include "typemap.h"
 #include "parse.h"
 #include "scan.h"
+#include "i18n.h"
+#include "normalize.h"
 
-static int verify_declspecs(struct cdecl_declspec *s)
+/*
+ * Verify the declaration specifiers of a declaration.  If top is true, treat
+ * this as a top-level declaration.  Otherwise, treat this as a function
+ * parameter (which carries additional constraints).
+ */
+static bool valid_declspecs(struct cdecl *decl, bool top)
 {
+	struct cdecl_declspec *specs = decl->specifiers;
+	struct cdecl_declarator *d   = decl->declarators;
+	bool abstract = cdecl_is_abstract(d);
 	unsigned num_storage = 0;
 	unsigned long typemap;
 
-	typemap = cdecl__build_typemap(s);
+	typemap = cdecl__build_typemap(specs);
 	if (typemap == -1)
-		return -1;
+		return false;
 
-	for (struct cdecl_declspec *c = s; c; c = c->next) {
+	for (struct cdecl_declspec *c = specs; c; c = c->next) {
 		switch (cdecl_spec_kind(c)) {
 		case CDECL_SPEC_TYPE:
+			if (c->type == CDECL_TYPE_VOID &&
+			    (d->type == CDECL_DECL_IDENT
+		             || d->type == CDECL_DECL_ARRAY)) {
+				fprintf(stderr, "invalid declaration of type void\n");
+				return false;
+			}
 			continue;
 		case CDECL_SPEC_STOR:
+			if (top && abstract) {
+				fprintf(stderr, "type names cannot have storage-class specifiers\n");
+				return false;
+			}
+
+			if (!top && c->type != CDECL_STOR_REGISTER) {
+				fprintf(stderr, "function parameters may only have register storage\n");
+				return false;
+			}
+
 			if (++num_storage > 1) {
 				fprintf(stderr, "too many storage-class specifiers\n");
-				return -1;
+				return false;
 			}
 			break;
 		case CDECL_SPEC_QUAL:
@@ -32,46 +77,460 @@ static int verify_declspecs(struct cdecl_declspec *s)
 			 */
 			if (c->type == CDECL_QUAL_RESTRICT) {
 				fprintf(stderr, "only pointer types can be restrict-qualified.\n");
-				return -1;
+				return false;
 			}
 			break;
 		case CDECL_SPEC_FUNC:
-			/*
-			 * We don't support functions yet.
-			 */
-			fprintf(stderr, "only function declarations may have function specifiers.\n");
-			return -1;
+			if (abstract) {
+				fprintf(stderr, "type names cannot have function specifiers\n");
+				return false;
+			}
+
+			if (!top || d->type != CDECL_DECL_FUNCTION) {
+				fprintf(stderr, "only function declarations may have function specifiers.\n");
+				return false;
+			}
+			break;
 		default:
 			assert(0);
 		}
 	}
 
+	return true;
+}
+
+/*
+ * The C grammar leaves ambiguous some cases where parentheses represent a
+ * function declarator or just parentheses.  The language uses additional
+ * context (whether or not a typedef is in scope, etc.) to resolve these
+ * ambiguities, but we don't have access to that kind of information.
+ *
+ * The cdecl99 parser uses an unambiguous grammar which treats almost
+ * everything as a function, and thus considers things like 'int (x)' to
+ * be a function type with a single parameter of type 'x' (a typedef name),
+ * returning int.  This can result in very complicated types for simple
+ * declarations.  Ideally, cdecl99 should try and find the "simplest"
+ * explanation for a given declaration.
+ *
+ * Whether or not it achieves the simplest explanation, we apply a simple rule:
+ * if a declarator could be interpreted as something other than a function,
+ * do that.
+ *
+ *   - The function declarator has a null child declarator.
+ *   - The function declarator has exactly one parameter, and is not variadic.
+ *   - The function parameter has a type specifier, and it is a typedef name.
+ *   - The function parameter has no other declaration specifiers.
+ *   - The function parameter does not declare an identifier.
+ *
+ * Since cdecl99 supports things like [*] in any context (in C, such constructs
+ * are only valid in function parameter lists), we don't treat them specially
+ * here.
+ */
+
+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;
+
+	for (last = decl; last && last->type != CDECL_DECL_NULL;)
+		last = last->child;
+
+	if (!last)
+		return NULL;
+
+	last->type = CDECL_DECL_IDENT;
+	last->u.ident = spec->ident;
+	free(param);
+	free(spec);
+
+	return decl;
+}
+
+static bool function_is_reducible(struct cdecl_declarator *d)
+{
+	if (d->type != CDECL_DECL_FUNCTION)
+		return false;
+	if (d->child->type != CDECL_DECL_NULL)
+		return false; /* e.g., int (*)(x) */
+
+	if (!d->u.function.parameters)
+		return false; /* e.g., int f() */
+	if (d->u.function.parameters->next)
+		return false; /* e.g., int (x, y) */
+	if (d->u.function.variadic)
+		return false; /* e.g., int (x, ...) */
+
+	if (d->u.function.parameters->specifiers->type != CDECL_TYPE_IDENT)
+		return false; /* e.g. int (int) */
+	if (d->u.function.parameters->specifiers->next)
+		return false; /* e.g. int (size_t const) */
+
+	return true;
+}
+
+static int
+simplify_functions(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+	struct cdecl_declarator *new;
+
+	if (!function_is_reducible(d))
+		return 0;
+
+	new = reduce_function(d->u.function.parameters);
+	if (!new)
+		return 0; /* e.g. int (foo bar) */
+	*p = new;
+	free(d->child);
+	free(d);
+
+	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.
+ *
+ * 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).
+ *
+ * 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.
+ */
+
+static int
+reduce_parentheses(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+	struct cdecl *param;
+
+	if (d->type != CDECL_DECL_FUNCTION)
+		return 0;
+
+	param = d->u.function.parameters;
+	if (param && param->specifiers == NULL) {
+		struct cdecl_declarator *decl;
+
+		assert(!param->next);
+
+		decl = param->declarators;
+		if (decl->type == CDECL_DECL_NULL) {
+			free(decl);
+			free(param);
+			d->u.function.parameters = NULL;
+			return 0;
+		}
+
+		if (d->child->type != CDECL_DECL_NULL) {
+			fprintf(stderr, "invalid function parameter\n");
+			return -1;
+		}
+
+		free(d->child);
+		free(param);
+		free(d);
+		*p = decl;
+
+		/*
+		 * We may have replaced d with another fake function which
+		 * also needs to be eliminated.
+		 */
+		if (reduce_parentheses(p, decl) < 0)
+			return -1;
+
+		/*
+		 * 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)) {
+			fprintf(stderr, "too many parentheses in function\n");
+			return -1;
+		}
+
+		return 1;
+	}
+
 	return 0;
 }
 
-static int verify_decl(struct cdecl *decl)
+/*
+ * Function parameters and return types have a few restrictions that are
+ * really easy to check in comparison to the above absurdity.
+ */
+static int
+check_parameters(struct cdecl_declarator **p, struct cdecl_declarator *d)
 {
-	return verify_declspecs(decl->specifiers);
+	struct cdecl_declspec *spec;
+	struct cdecl *param;
+	bool has_void = false;
+
+	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) {
+				fprintf(stderr, "void parameter must not have extra specifiers\n");
+				return -1;
+			} else if (d->u.function.parameters->next) {
+				fprintf(stderr, "a void parameter must stand alone\n");
+				return -1;
+			} else if (d->u.function.variadic) {
+				fprintf(stderr, "variadic functions cannot have a void parameter\n");
+				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.
+ */
+static int
+check_rettypes(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+	if (!d->child || d->child->type != CDECL_DECL_FUNCTION)
+		return 0;
+
+	switch (d->type) {
+	case CDECL_DECL_FUNCTION:
+		fprintf(stderr, "functions cannot return functions\n");
+		return -1;
+	case CDECL_DECL_ARRAY:
+		fprintf(stderr, "functions cannot return arrays\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+static int
+check_arrays(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+	if (!d->child || d->child->type != CDECL_DECL_ARRAY)
+		return 0;
+
+	switch (d->type) {
+	case CDECL_DECL_FUNCTION:
+		fprintf(stderr, "array members cannot be functions\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+static int
+normalize_specs(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+	struct cdecl_function *func;
+	struct cdecl_pointer *ptr;
+
+	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;
+	}
+
+	return 0;
+}
+
+static int
+check_qualifiers(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)
+		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) {
+			fprintf(stderr, "function pointers cannot be restrict-qualified\n");
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Traverse the parse tree, calling a function on every declarator in a
+ * depth-first preorder traversal.  The function is given a pointer to the
+ * declarator as well as to the pointer which was used to reach that
+ * declarator: this can be used to rewrite entire subtrees.
+ */
+static bool forall_declarators(struct cdecl *decl,
+	int f(struct cdecl_declarator **, struct cdecl_declarator *))
+{
+	struct cdecl_declarator *d, **p;
+
+	for (p = &decl->declarators, d = *p; d; p = &d->child, d = *p) {
+		switch (f(p, d)) {
+		case 0:
+			break;
+		case 1:
+			d = *p;
+			break;
+		case -1:
+			return false;
+		default:
+			assert(0);
+		}
+
+		if (d->type == CDECL_DECL_FUNCTION) {
+			struct cdecl *i;
+
+			for (i = d->u.function.parameters; i; i = i->next) {
+				if (!forall_declarators(i, f))
+					return false;
+			}
+		}
+	}
+
+	return true;
 }
 
 struct cdecl *cdecl_parse_decl(const char *declstr)
 {
+	struct cdecl_declspec *norm_specs;
 	YY_BUFFER_STATE state;
+	yyscan_t scanner;
 	struct cdecl *decl;
 	int rc;
 
-	state = yy_scan_string(declstr);
-	rc = yyparse(&decl);
-	yy_delete_buffer(state);
+	cdecl__init_i18n();
 
+	rc = cdecl__yylex_init(&scanner);
 	if (rc != 0)
 		return NULL;
 
-	rc = verify_decl(decl);
-	if (rc != 0) {
-		cdecl_free(decl);
+	state = cdecl__yy_scan_string(declstr, scanner);
+	rc = cdecl__yyparse(scanner, &decl);
+	cdecl__yy_delete_buffer(state, scanner);
+	cdecl__yylex_destroy(scanner);
+
+	if (rc != 0)
 		return NULL;
+
+	/*
+	 * Since the top-level specifiers are shared between each top-level
+	 * declarator, we need to normalize them once and then propagate the
+	 * new specifier list.
+	 */
+	norm_specs = cdecl__normalize_specs(decl->specifiers);
+
+	for (struct cdecl *i = decl; i; i = i->next) {
+		i->specifiers = norm_specs;
+
+		if (!forall_declarators(i, reduce_parentheses))
+			goto err;
+		if (!forall_declarators(i, simplify_functions))
+			goto err;
+		if (!forall_declarators(i, check_parameters))
+			goto err;
+		if (!forall_declarators(i, check_rettypes))
+			goto err;
+		if (!forall_declarators(i, check_arrays))
+			goto err;
+		if (!forall_declarators(i, normalize_specs))
+			goto err;
+		if (!forall_declarators(i, check_qualifiers))
+			goto err;
+
+		if (!valid_declspecs(i, true))
+			goto err;
+
+		if (cdecl_is_abstract(i->declarators)
+		    && (i != decl || i->next)) {
+			fprintf(stderr, "mixing type names and declarations is not allowed\n");
+			goto err;
+		}
 	}
 
 	return decl;
+err:
+	cdecl__free(decl);
+	return NULL;
+}
+
+struct cdecl *cdecl_parse_english(const char *english)
+{
+	YY_BUFFER_STATE state;
+	yyscan_t scanner;
+	struct cdecl *decl;
+	int rc;
+
+	cdecl__init_i18n();
+
+	rc = cdecl__yylex_init_extra(true, &scanner);
+	if (rc != 0)
+		return NULL;
+
+	state = cdecl__yy_scan_string(english, scanner);
+	rc = cdecl__yyparse(scanner, &decl);
+	cdecl__yy_delete_buffer(state, scanner);
+	cdecl__yylex_destroy(scanner);
+
+	if (rc != 0)
+		return NULL;
+
+	for (struct cdecl *i = decl; i; i = i->next) {
+		i->specifiers = cdecl__normalize_specs(i->specifiers);
+
+		if (!forall_declarators(i, check_parameters))
+			goto err;
+		if (!forall_declarators(i, check_rettypes))
+			goto err;
+		if (!forall_declarators(i, check_arrays))
+			goto err;
+		if (!forall_declarators(i, normalize_specs))
+			goto err;
+		if (!forall_declarators(i, check_qualifiers))
+			goto err;
+
+		if (!valid_declspecs(i, true))
+			goto err;
+	}
+
+	return decl;
+err:
+	cdecl__free(decl);
+	return NULL;
+}
+
+void cdecl_free(struct cdecl *decl)
+{
+	cdecl__free(decl);
 }