*/
#include <stdio.h>
#include <assert.h>
+#include <stdbool.h>
#include "cdecl.h"
#include "typemap.h"
return 0;
}
-static int verify_decl(struct cdecl *decl)
+/*
+ * 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;
+}
+
+/*
+ * 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 *))
{
- return verify_declspecs(decl->specifiers);
+ 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)
if (rc != 0)
return NULL;
- rc = verify_decl(decl);
- if (rc != 0) {
- cdecl_free(decl);
- return NULL;
+ if (verify_declspecs(decl->specifiers) != 0)
+ goto err;
+
+ 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;
}
return decl;
+err:
+ cdecl_free(decl);
+ return NULL;
}
projects / cdecl99.git / blobdiff