+/*
+ * Parse and validate C declarations.
+ * Copyright © 2011-2012, 2020-2021, 2023-2024 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"
+
+static struct cdecl *fake_function_param(struct cdecl_declarator *);
-static int verify_specs(struct cdecl_declspec *s)
+/*
+ * 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)
{
- unsigned num_storage = 0;
- unsigned long typemap;
+ struct parse_item *ret;
- typemap = cdecl__build_typemap(s);
- if (typemap == -1)
- return -1;
+ ret = malloc(offsetof(struct parse_item, s) + s_sz);
+ if (!ret) {
+ cdecl__errmsg(CDECL__ENOMEM);
+ return NULL;
+ }
- if (!cdecl__typemap_is_valid(typemap)) {
- fprintf(stderr, "conflicting type specifiers\n");
- return -1;
+ 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;
}
- for (struct cdecl_declspec *c = s; c; c = c->next) {
+ if (typemap_is_valid(map))
+ return true;
+
+ if (map == 0)
+ cdecl__errmsg(CDECL__ENOTYPE);
+ else
+ cdecl__errmsg(CDECL__EBADTYPE);
+
+ 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 *c, *specs = decl->specifiers;
+ struct cdecl_declarator *d = decl->declarators;
+ bool abstract = cdecl_is_abstract(d);
+ unsigned num_storage = 0;
+
+ if (!valid_typespec(specs))
+ return false;
+
+ 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;
+}
+
+/*
+ * Find the tree pointer which leads to the parameter's leaf node.
+ *
+ * Return a null pointer if the traversal locates a syntactic element which
+ * prevents function reduction. This occurs if the leaf node declares an
+ * identifier, or for nontrivial fake function parameters (see below).
+ */
+static struct cdecl_declarator **leaf_pointer(struct cdecl *param)
+{
+ struct cdecl_declarator *d, **p = ¶m->declarators;
+
+ if ((param = fake_function_param(param->declarators))) {
+ if (param->declarators->type != CDECL_DECL_NULL)
+ return NULL; /* e.g. int (x (*)) */
+ }
+
+ while ((d = *p)->child) {
+ p = &d->child;
+
+ if (fake_function_param(d->child))
+ return NULL; /* e.g. int (x (*)[][1]) */
+ }
+
+ if (d->type != CDECL_DECL_NULL)
+ return NULL; /* e.g. int (x y) */
+
+ return p;
+}
+
+
+/*
+ * 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 parse_item *spec = (void *)param->specifiers;
+ struct cdecl_declarator *d, **p;
+
+ if (!(p = leaf_pointer(param)))
+ 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;
+ *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 (rc != 0)
+ 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;
+}
+
+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;
+
+ 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;
- rc = verify_decl(decl);
- if (rc != 0) {
- cdecl_free(decl);
+ 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);
+}
projects / cdecl99.git / blobdiff