X-Git-Url: https://git.draconx.ca/gitweb/cdecl99.git/blobdiff_plain/90d2c82cd8b19562c71965d1bfa8e4b612ea4026..ad973d63e038f293f2b158f19b04c1582e616af0:/src/parse-decl.c

diff --git a/src/parse-decl.c b/src/parse-decl.c
index 39a3e3c..f00442d 100644
--- a/src/parse-decl.c
+++ b/src/parse-decl.c
@@ -1,78 +1,586 @@
+/*
+ * Parse and validate C declarations.
+ * Copyright © 2011-2012, 2020-2021 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 <https://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
 #include <stdio.h>
 #include <assert.h>
+#include <stdbool.h>
 
 #include "cdecl.h"
-#include "typemap.h"
+#include "cdecl-internal.h"
 #include "parse.h"
 #include "scan.h"
 
-static int verify_specs(struct cdecl_declspec *s)
+/*
+ * We can represent type specifiers as a bitmap, which gives us a finite
+ * list of acceptable bitmap values according to the C standard.  However,
+ * the "long" specifier is allowed to occur more than once, but only at most
+ * 2 times.  Treat it as a special case, assigning an unused bit to represent
+ * the second long.
+ */
+#define MAP_LLONG_BIT 31
+#define MAP_LONG_BIT (CDECL_TYPE_LONG-CDECL_SPEC_TYPE)
+#define CDECL_TYPE_LLONG (CDECL_SPEC_TYPE+MAP_LLONG_BIT)
+
+#include "typemap.h"
+
+/*
+ * Convert the declaration specifiers to a bitmap with each bit
+ * corresponding to one specific type specifier.
+ */
+static int valid_typespec(struct cdecl_declspec *s)
+{
+	unsigned long map = 0;
+
+	for (struct cdecl_declspec *c = s; c; c = c->next) {
+		unsigned long bit;
+
+		if (cdecl_spec_kind(c) != CDECL_SPEC_TYPE)
+			continue;
+
+		bit = c->type - CDECL_SPEC_TYPE;
+		assert(bit < MAP_LLONG_BIT);
+		bit = 1ul << bit;
+
+		/* "long" special case */
+		if ((map & bit) == 1ul << MAP_LONG_BIT)
+			bit = 1ul << MAP_LLONG_BIT;
+
+		if (map & bit) {
+			if (bit == 1ul << MAP_LLONG_BIT)
+				cdecl__err(CDECL_EBADTYPE, _("too many long specifiers"));
+			else
+				cdecl__err(CDECL_EBADTYPE, _("duplicate type specifier"));
+			return false;
+		}
+		map |= bit;
+	}
+
+	if (typemap_is_valid(map))
+		return true;
+
+	if (map == 0)
+		cdecl__err(CDECL_EBADTYPE, _("no type specified"));
+	else
+		cdecl__err(CDECL_EBADTYPE, _("invalid type specified"));
+
+	return false;
+}
+
+/*
+ * 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);
-	if (typemap == -1)
-		return -1;
+	if (!valid_typespec(specs))
+		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)) {
+				cdecl__err(CDECL_EBADTYPE, _("invalid declaration of type void"));
+				return false;
+			}
 			continue;
 		case CDECL_SPEC_STOR:
+			if (top && abstract) {
+				cdecl__err(CDECL_EBADSTOR, _("type names cannot have storage-class specifiers"));
+				return false;
+			}
+
+			if (!top && c->type != CDECL_STOR_REGISTER) {
+				cdecl__err(CDECL_EBADSTOR, _("function parameters may only have register storage"));
+				return false;
+			}
+
 			if (++num_storage > 1) {
-				fprintf(stderr, "too many storage-class specifiers\n");
-				return -1;
+				cdecl__err(CDECL_EBADSTOR, _("too many storage-class specifiers"));
+				return false;
 			}
 			break;
 		case CDECL_SPEC_QUAL:
 			/*
-			 * Since we don't support pointer types yet, all
-			 * restrict qualifiers are invalid.  Other qualifiers
-			 * are always valid.
+			 * Restrict qualifiers are only valid in the
+			 * pointer qualifier list, which isn't checked here.
 			 */
 			if (c->type == CDECL_QUAL_RESTRICT) {
-				fprintf(stderr, "only pointer types can be restrict-qualified.\n");
-				return -1;
+				cdecl__err(CDECL_EBADQUAL, _("only pointer types can be restrict-qualified"));
+				return false;
 			}
 			break;
 		case CDECL_SPEC_FUNC:
-			/*
-			 * Likewise for function specifiers.
-			 */
-			fprintf(stderr, "only function declarations may have function specifiers.\n");
-			return -1;
+			if (abstract) {
+				cdecl__err(CDECL_ENOTFUNC, _("type names cannot have function specifiers"));
+				return false;
+			}
+
+			if (!top || d->type != CDECL_DECL_FUNCTION) {
+				cdecl__err(CDECL_ENOTFUNC, _("only function declarations can have function specifiers"));
+				return false;
+			}
+			break;
 		default:
-			abort();
+			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.
+ *
+ * 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) */
+	if (d->u.function.parameters->declarators->type == CDECL_DECL_POINTER)
+		return false; /* e.g. int (x *) */
+
+	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) {
+			cdecl__err(CDECL_EBADPARAMS, _("invalid function parameter"));
+			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)) {
+			cdecl__err(CDECL_EBADPARAMS, _("too many parentheses in function"));
+			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_specs(decl->specifiers);
+	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__err(CDECL_EVOIDPARAM, _("void parameter cannot have extra specifiers"));
+				return -1;
+			} else if (d->u.function.parameters->next) {
+				cdecl__err(CDECL_EVOIDPARAM, _("void parameter must stand alone"));
+				return -1;
+			} else if (d->u.function.variadic) {
+				cdecl__err(CDECL_EVOIDPARAM, _("variadic function cannot have void parameter"));
+				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:
+		cdecl__err(CDECL_EBADRETURN, _("functions cannot return functions"));
+		return -1;
+	case CDECL_DECL_ARRAY:
+		cdecl__err(CDECL_EBADRETURN, _("functions cannot return arrays"));
+		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:
+		cdecl__err(CDECL_EBADARRAY, _("array members cannot be functions"));
+		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) {
+			cdecl__err(CDECL_EBADPOINTER, _("function pointers cannot be restrict-qualified"));
+			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;
+
+	cdecl__init_i18n();
+
+	rc = cdecl__yylex_init(&scanner);
+	if (rc != 0)
+		return NULL;
+
+	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;
+	}
+
+	/* Now perform checks and simplifications on each declarator. */
+	for (struct cdecl *i = decl; i; i = i->next) {
+		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)) {
+			cdecl__err(CDECL_EBADDECL, _("mixing type names and declarations is not allowed"));
+			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;
 
-	state = yy_scan_string(declstr);
-	rc = yyparse(&decl);
-	yy_delete_buffer(state);
+	cdecl__init_i18n();
 
+	rc = cdecl__yylex_init_extra(true, &scanner);
 	if (rc != 0)
 		return NULL;
 
-	rc = verify_decl(decl);
-	if (rc != 0) {
-		cdecl_free(decl);
+	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);
 }