X-Git-Url: https://git.draconx.ca/gitweb/cdecl99.git/blobdiff_plain/90d2c82cd8b19562c71965d1bfa8e4b612ea4026..09d517aa84f99c3686803d156cde10fc0c02bdc2:/src/parse-decl.c

diff --git a/src/parse-decl.c b/src/parse-decl.c
index 39a3e3c..8f0bd38 100644
--- a/src/parse-decl.c
+++ b/src/parse-decl.c
@@ -1,78 +1,600 @@
+/*
+ * Parse and validate C declarations.
+ * Copyright © 2011-2012, 2020-2021, 2023 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"
+#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,
+ * 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)
+{
+	struct cdecl_declspec *c;
+	unsigned long map = 0;
+
+	for (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__errmsg(CDECL__ETOOLONG);
+			else
+				cdecl__errmsg(CDECL__EDUPTYPE);
+			return false;
+		}
+		map |= bit;
+	}
+
+	if (typemap_is_valid(map))
+		return true;
+
+	if (map == 0)
+		cdecl__errmsg(CDECL__ENOTYPE);
+	else
+		cdecl__errmsg(CDECL__EBADTYPE);
+
+	return false;
+}
 
-static int verify_specs(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 *c, *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 (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__errmsg(CDECL__EBADVOID);
+				return false;
+			}
 			continue;
 		case CDECL_SPEC_STOR:
+			if (top && abstract) {
+				cdecl__errmsg(CDECL__ETYPESTOR);
+				return false;
+			}
+
+			if (!top && c->type != CDECL_STOR_REGISTER) {
+				cdecl__errmsg(CDECL__EFUNCSTOR);
+				return false;
+			}
+
 			if (++num_storage > 1) {
-				fprintf(stderr, "too many storage-class specifiers\n");
-				return -1;
+				cdecl__errmsg(CDECL__EMANYSTOR);
+				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__errmsg(CDECL__EBADQUAL);
+				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 || !top || d->type != CDECL_DECL_FUNCTION) {
+				cdecl__errmsg(CDECL__ENOTFUNC);
+				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_declarator *d, **p = &param->declarators;
+	struct parse_item *spec = (void *)param->specifiers;
+
+	while ((d = *p)->child)
+		p = &d->child;
+
+	if (d->type != CDECL_DECL_NULL)
+		return NULL;
+
+	/*
+	 * 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;
+
+	d = param->declarators;
+	free(param);
+	return d;
+}
+
+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);
+
+	return 1;
+}
+
+/*
+ * 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:
+ *
+ *   - 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 struct cdecl *fake_function_param(struct cdecl_declarator *d)
+{
+	struct cdecl *param;
+
+	if (d->type != CDECL_DECL_FUNCTION)
+		return NULL;
+
+	param = d->u.function.parameters;
+	if (!param || param->specifiers)
+		return NULL;
+
+	assert(!param->next);
+	return param;
+}
+
+static int
+reduce_parentheses(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+	struct cdecl *param;
+
+	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;
+			}
+
+			cdecl__free(param);
+		}
+	} while (simplify_functions(p, d));
+
 	return 0;
 }
 
-static int verify_decl(struct cdecl *decl)
+/*
+ * Returns nonzero iff the given specifier list contains a specifier
+ * of the indicated type.
+ */
+static int have_specifier(struct cdecl_declspec *s, unsigned type)
 {
-	return verify_specs(decl->specifiers);
+	for (; s; s = s->next)
+		if (s->type == type)
+			return 1;
+	return 0;
 }
 
-struct cdecl *cdecl_parse_decl(const char *declstr)
+/*
+ * 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_function_child(struct cdecl_declarator *d)
 {
-	YY_BUFFER_STATE state;
-	struct cdecl *decl;
+	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:
+		/* array of function is never allowed. */
+		cdecl__errmsg(CDECL__EFUNCARRAY);
+		return -1;
+	}
+
+	return 0;
+}
+
+/*
+ * 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 (!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;
+}
+
+/*
+ * 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 = &d->u.function;
+	struct cdecl *param;
 	int rc;
 
-	state = yy_scan_string(declstr);
-	rc = yyparse(&decl);
-	yy_delete_buffer(state);
+	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 check_function_child(d->child);
+}
+
+static int
+postproc_common(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+	struct cdecl_pointer *ptr;
+
+	switch (d->type) {
+	case CDECL_DECL_POINTER:
+		ptr = &d->u.pointer;
+		ptr->qualifiers = cdecl__normalize_specs(ptr->qualifiers);
+		return 0;
+	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;
+}
+
+/*
+ * 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.
+ *
+ * The called function may return a negative value to indicate an error
+ * which terminates traversal.
+ *
+ * Returns 0 on success, or a negative value on failure.
+ */
+static int forall_declarators(struct cdecl *decl,
+	int f(struct cdecl_declarator **, struct cdecl_declarator *))
+{
+	struct cdecl_declarator *d, **p;
+
+	for (p = &decl->declarators; *p; p = &d->child) {
+		int rc;
+
+		rc = f(p, *p);
+		if (rc < 0)
+			return rc;
+		d = *p;
+
+		if (d->type == CDECL_DECL_FUNCTION) {
+			struct cdecl *i;
+
+			for (i = d->u.function.parameters; i; i = i->next) {
+				rc = forall_declarators(i, f);
+				if (rc < 0)
+					return rc;
+			}
+		}
+	}
+
+	return 0;
+}
 
-	if (rc != 0)
+static struct cdecl *do_parse(const char *str, int english_mode)
+{
+	struct cdecl *decl = NULL;
+	YY_BUFFER_STATE state;
+	yyscan_t scanner;
+
+#if YYDEBUG
+	extern int cdecl__yydebug;
+	cdecl__yydebug = 1;
+#endif
+
+	cdecl__init_i18n();
+	if (cdecl__yylex_init_extra(english_mode, &scanner) != 0)
 		return NULL;
 
-	rc = verify_decl(decl);
-	if (rc != 0) {
-		cdecl_free(decl);
+	state = cdecl__yy_scan_string(str, scanner);
+	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);
+
+	return decl;
+}
+
+static int do_postprocess(struct cdecl *decl, int english_mode)
+{
+	struct cdecl_declspec *norm_specs;
+	struct cdecl *i;
+
+	/*
+	 * For a C declaration with more than one full declarator, the
+	 * specifier list is common to all of them.  Normalize it once,
+	 * then propagate that to all the linked cdecl structures.
+	 *
+	 * In english mode, the cdecl structure list always has exactly
+	 * one entry so we don't need to do anything differently.
+	 */
+	norm_specs = cdecl__normalize_specs(decl->specifiers);
+	for (i = decl; i; i = i->next)
+		i->specifiers = norm_specs;
+
+	for (i = decl; i; i = i->next) {
+		if (!english_mode) {
+			if (forall_declarators(i, reduce_parentheses) < 0)
+				return 0;
+		}
+
+		if (forall_declarators(i, postproc_common) < 0)
+			return 0;
+
+		if (!valid_declspecs(i, true))
+			return 0;
+
+		if (decl->next && cdecl_is_abstract(i->declarators)) {
+			/* Abstract full declarators: there can only be one. */
+			cdecl__errmsg(CDECL__EDECLTYPE);
+			return 0;
+		}
+	}
+
+	return 1;
+}
+
+static struct cdecl *parse_common(const char *str, int english_mode)
+{
+	struct cdecl *decl;
+
+	if (!(decl = do_parse(str, english_mode)))
+		return NULL;
+
+	if (!do_postprocess(decl, english_mode)) {
+		cdecl__free(decl);
 		return NULL;
 	}
 
 	return decl;
 }
+
+struct cdecl *cdecl_parse_decl(const char *declstr)
+{
+	return parse_common(declstr, false);
+}
+
+struct cdecl *cdecl_parse_english(const char *english)
+{
+	return parse_common(english, true);
+}
+
+void cdecl_free(struct cdecl *decl)
+{
+	cdecl__free(decl);
+}