/*
* 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 .
*/
#include
#include
#include
#include
#include "cdecl.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;
}
/*
* 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) {
cdecl__errmsg(CDECL__EMANYSTOR);
return false;
}
break;
case CDECL_SPEC_QUAL:
/*
* Restrict qualifiers are only valid in the
* pointer qualifier list, which isn't checked here.
*/
if (c->type == CDECL_QUAL_RESTRICT) {
cdecl__errmsg(CDECL__EBADQUAL);
return false;
}
break;
case CDECL_SPEC_FUNC:
if (abstract || !top || d->type != CDECL_DECL_FUNCTION) {
cdecl__errmsg(CDECL__ENOTFUNC);
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.
*
* 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 = ¶m->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;
}
/*
* Returns nonzero iff the given specifier list contains a specifier
* of the indicated type.
*/
static int have_specifier(struct cdecl_declspec *s, unsigned type)
{
for (; s; s = s->next)
if (s->type == type)
return 1;
return 0;
}
/*
* 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)
{
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;
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;
}
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;
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);
}