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chibicc/parse.c

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// This file contains a recursive descent parser for C.
//
// Most functions in this file are named after the symbols they are
// supposed to read from an input token list. For example, stmt() is
// responsible for reading a statement from a token list. The function
// then construct an AST node representing a statement.
//
// Each function conceptually returns two values, an AST node and
// remaining part of the input tokens. Since C doesn't support
// multiple return values, the remaining tokens are returned to the
// caller via a pointer argument.
//
// Input tokens are represented by a linked list. Unlike many recursive
// descent parsers, we don't have the notion of the "input token stream".
// Most parsing functions don't change the global state of the parser.
// So it is very easy to lookahead arbitrary number of tokens in this
// parser.
#include "chibicc.h"
// Scope for local variables, global variables, typedefs
// or enum constants
typedef struct VarScope VarScope;
struct VarScope {
VarScope *next;
char *name;
Obj *var;
Type *type_def;
Type *enum_ty;
int enum_val;
};
// Scope for struct, union or enum tags
typedef struct TagScope TagScope;
struct TagScope {
TagScope *next;
char *name;
Type *ty;
};
// Represents a block scope.
typedef struct Scope Scope;
struct Scope {
Scope *next;
// C has two block scopes; one is for variables/typedefs and
// the other is for struct/union/enum tags.
VarScope *vars;
TagScope *tags;
};
// Variable attributes such as typedef or extern.
typedef struct {
bool is_typedef;
bool is_static;
bool is_extern;
bool is_inline;
bool is_tls;
int align;
} VarAttr;
// This struct represents a variable initializer. Since initializers
// can be nested (e.g. `int x[2][2] = {{1, 2}, {3, 4}}`), this struct
// is a tree data structure.
typedef struct Initializer Initializer;
struct Initializer {
Initializer *next;
Type *ty;
Token *tok;
bool is_flexible;
// If it's not an aggregate type and has an initializer,
// `expr` has an initialization expression.
Node *expr;
// If it's an initializer for an aggregate type (e.g. array or struct),
// `children` has initializers for its children.
Initializer **children;
// Only one member can be initialized for a union.
// `mem` is used to clarify which member is initialized.
Member *mem;
};
// For local variable initializer.
typedef struct InitDesg InitDesg;
struct InitDesg {
InitDesg *next;
int idx;
Member *member;
Obj *var;
};
// All local variable instances created during parsing are
// accumulated to this list.
static Obj *locals;
// Likewise, global variables are accumulated to this list.
static Obj *globals;
static Scope *scope = &(Scope){};
// Points to the function object the parser is currently parsing.
static Obj *current_fn;
// Lists of all goto statements and labels in the curent function.
static Node *gotos;
static Node *labels;
// Current "goto" and "continue" jump targets.
static char *brk_label;
static char *cont_label;
// Points to a node representing a switch if we are parsing
// a switch statement. Otherwise, NULL.
static Node *current_switch;
static Obj *builtin_alloca;
static bool is_typename(Token *tok);
static Type *declspec(Token **rest, Token *tok, VarAttr *attr);
static Type *typename(Token **rest, Token *tok);
static Type *enum_specifier(Token **rest, Token *tok);
static Type *typeof_specifier(Token **rest, Token *tok);
static Type *type_suffix(Token **rest, Token *tok, Type *ty);
static Type *declarator(Token **rest, Token *tok, Type *ty);
static Node *declaration(Token **rest, Token *tok, Type *basety, VarAttr *attr);
static void array_initializer2(Token **rest, Token *tok, Initializer *init, int i);
static void struct_initializer2(Token **rest, Token *tok, Initializer *init, Member *mem);
static void initializer2(Token **rest, Token *tok, Initializer *init);
static Initializer *initializer(Token **rest, Token *tok, Type *ty, Type **new_ty);
static Node *lvar_initializer(Token **rest, Token *tok, Obj *var);
static void gvar_initializer(Token **rest, Token *tok, Obj *var);
static Node *compound_stmt(Token **rest, Token *tok);
static Node *stmt(Token **rest, Token *tok);
static Node *expr_stmt(Token **rest, Token *tok);
static Node *expr(Token **rest, Token *tok);
static int64_t eval(Node *node);
static int64_t eval2(Node *node, char **label);
static int64_t eval_rval(Node *node, char **label);
static bool is_const_expr(Node *node);
static Node *assign(Token **rest, Token *tok);
static Node *logor(Token **rest, Token *tok);
static double eval_double(Node *node);
static Node *conditional(Token **rest, Token *tok);
static Node *logand(Token **rest, Token *tok);
static Node *bitor(Token **rest, Token *tok);
static Node *bitxor(Token **rest, Token *tok);
static Node *bitand(Token **rest, Token *tok);
static Node *equality(Token **rest, Token *tok);
static Node *relational(Token **rest, Token *tok);
static Node *shift(Token **rest, Token *tok);
static Node *add(Token **rest, Token *tok);
static Node *new_add(Node *lhs, Node *rhs, Token *tok);
static Node *new_sub(Node *lhs, Node *rhs, Token *tok);
static Node *mul(Token **rest, Token *tok);
static Node *cast(Token **rest, Token *tok);
static Member *get_struct_member(Type *ty, Token *tok);
static Type *struct_decl(Token **rest, Token *tok);
static Type *union_decl(Token **rest, Token *tok);
static Node *postfix(Token **rest, Token *tok);
static Node *funcall(Token **rest, Token *tok, Node *node);
static Node *unary(Token **rest, Token *tok);
static Node *primary(Token **rest, Token *tok);
static Token *parse_typedef(Token *tok, Type *basety);
static bool is_function(Token *tok);
static Token *function(Token *tok, Type *basety, VarAttr *attr);
static Token *global_variable(Token *tok, Type *basety, VarAttr *attr);
static int align_down(int n, int align) {
return align_to(n - align + 1, align);
}
static void enter_scope(void) {
Scope *sc = calloc(1, sizeof(Scope));
sc->next = scope;
scope = sc;
}
static void leave_scope(void) {
scope = scope->next;
}
// Find a variable by name.
static VarScope *find_var(Token *tok) {
for (Scope *sc = scope; sc; sc = sc->next)
for (VarScope *sc2 = sc->vars; sc2; sc2 = sc2->next)
if (equal(tok, sc2->name))
return sc2;
return NULL;
}
static Type *find_tag(Token *tok) {
for (Scope *sc = scope; sc; sc = sc->next)
for (TagScope *sc2 = sc->tags; sc2; sc2 = sc2->next)
if (equal(tok, sc2->name))
return sc2->ty;
return NULL;
}
static Node *new_node(NodeKind kind, Token *tok) {
Node *node = calloc(1, sizeof(Node));
node->kind = kind;
node->tok = tok;
return node;
}
static Node *new_binary(NodeKind kind, Node *lhs, Node *rhs, Token *tok) {
Node *node = new_node(kind, tok);
node->lhs = lhs;
node->rhs = rhs;
return node;
}
static Node *new_unary(NodeKind kind, Node *expr, Token *tok) {
Node *node = new_node(kind, tok);
node->lhs = expr;
return node;
}
static Node *new_num(int64_t val, Token *tok) {
Node *node = new_node(ND_NUM, tok);
node->val = val;
return node;
}
static Node *new_long(int64_t val, Token *tok) {
Node *node = new_node(ND_NUM, tok);
node->val = val;
node->ty = ty_long;
return node;
}
static Node *new_ulong(long val, Token *tok) {
Node *node = new_node(ND_NUM, tok);
node->val = val;
node->ty = ty_ulong;
return node;
}
static Node *new_var_node(Obj *var, Token *tok) {
Node *node = new_node(ND_VAR, tok);
node->var = var;
return node;
}
static Node *new_vla_ptr(Obj *var, Token *tok) {
Node *node = new_node(ND_VLA_PTR, tok);
node->var = var;
return node;
}
Node *new_cast(Node *expr, Type *ty) {
add_type(expr);
Node *node = calloc(1, sizeof(Node));
node->kind = ND_CAST;
node->tok = expr->tok;
node->lhs = expr;
node->ty = copy_type(ty);
return node;
}
static VarScope *push_scope(char *name) {
VarScope *sc = calloc(1, sizeof(VarScope));
sc->name = name;
sc->next = scope->vars;
scope->vars = sc;
return sc;
}
static Initializer *new_initializer(Type *ty, bool is_flexible) {
Initializer *init = calloc(1, sizeof(Initializer));
init->ty = ty;
if (ty->kind == TY_ARRAY) {
if (is_flexible && ty->size < 0) {
init->is_flexible = true;
return init;
}
init->children = calloc(ty->array_len, sizeof(Initializer *));
for (int i = 0; i < ty->array_len; i++)
init->children[i] = new_initializer(ty->base, false);
return init;
}
if (ty->kind == TY_STRUCT || ty->kind == TY_UNION) {
// Count the number of struct members.
int len = 0;
for (Member *mem = ty->members; mem; mem = mem->next)
len++;
init->children = calloc(len, sizeof(Initializer *));
for (Member *mem = ty->members; mem; mem = mem->next) {
if (is_flexible && ty->is_flexible && !mem->next) {
Initializer *child = calloc(1, sizeof(Initializer));
child->ty = mem->ty;
child->is_flexible = true;
init->children[mem->idx] = child;
} else {
init->children[mem->idx] = new_initializer(mem->ty, false);
}
}
return init;
}
return init;
}
static Obj *new_var(char *name, Type *ty) {
Obj *var = calloc(1, sizeof(Obj));
var->name = name;
var->ty = ty;
var->align = ty->align;
push_scope(name)->var = var;
return var;
}
static Obj *new_lvar(char *name, Type *ty) {
Obj *var = new_var(name, ty);
var->is_local = true;
var->next = locals;
locals = var;
return var;
}
static Obj *new_gvar(char *name, Type *ty) {
Obj *var = new_var(name, ty);
var->next = globals;
var->is_static = true;
var->is_definition = true;
globals = var;
return var;
}
static char *new_unique_name(void) {
static int id = 0;
return format(".L..%d", id++);
}
static Obj *new_anon_gvar(Type *ty) {
return new_gvar(new_unique_name(), ty);
}
static Obj *new_string_literal(char *p, Type *ty) {
Obj *var = new_anon_gvar(ty);
var->init_data = p;
return var;
}
static char *get_ident(Token *tok) {
if (tok->kind != TK_IDENT)
error_tok(tok, "expected an identifier");
return strndup(tok->loc, tok->len);
}
static Type *find_typedef(Token *tok) {
if (tok->kind == TK_IDENT) {
VarScope *sc = find_var(tok);
if (sc)
return sc->type_def;
}
return NULL;
}
static void push_tag_scope(Token *tok, Type *ty) {
TagScope *sc = calloc(1, sizeof(TagScope));
sc->name = strndup(tok->loc, tok->len);
sc->ty = ty;
sc->next = scope->tags;
scope->tags = sc;
}
// declspec = ("void" | "_Bool" | "char" | "short" | "int" | "long"
// | "typedef" | "static" | "extern" | "inline"
// | "_Thread_local" | "__thread"
// | "signed" | "unsigned"
// | struct-decl | union-decl | typedef-name
// | enum-specifier | typeof-specifier
// | "const" | "volatile" | "auto" | "register" | "restrict"
// | "__restrict" | "__restrict__" | "_Noreturn")+
//
// The order of typenames in a type-specifier doesn't matter. For
// example, `int long static` means the same as `static long int`.
// That can also be written as `static long` because you can omit
// `int` if `long` or `short` are specified. However, something like
// `char int` is not a valid type specifier. We have to accept only a
// limited combinations of the typenames.
//
// In this function, we count the number of occurrences of each typename
// while keeping the "current" type object that the typenames up
// until that point represent. When we reach a non-typename token,
// we returns the current type object.
static Type *declspec(Token **rest, Token *tok, VarAttr *attr) {
// We use a single integer as counters for all typenames.
// For example, bits 0 and 1 represents how many times we saw the
// keyword "void" so far. With this, we can use a switch statement
// as you can see below.
enum {
VOID = 1 << 0,
BOOL = 1 << 2,
CHAR = 1 << 4,
SHORT = 1 << 6,
INT = 1 << 8,
LONG = 1 << 10,
FLOAT = 1 << 12,
DOUBLE = 1 << 14,
OTHER = 1 << 16,
SIGNED = 1 << 17,
UNSIGNED = 1 << 18,
};
Type *ty = ty_int;
int counter = 0;
while (is_typename(tok)) {
// Handle storage class specifiers.
if (equal(tok, "typedef") || equal(tok, "static") || equal(tok, "extern") ||
equal(tok, "inline") || equal(tok, "_Thread_local") || equal(tok, "__thread")) {
if (!attr)
error_tok(tok, "storage class specifier is not allowed in this context");
if (equal(tok, "typedef"))
attr->is_typedef = true;
else if (equal(tok, "static"))
attr->is_static = true;
else if (equal(tok, "extern"))
attr->is_extern = true;
else if (equal(tok, "inline"))
attr->is_inline = true;
else
attr->is_tls = true;
if (attr->is_typedef &&
attr->is_static + attr->is_extern + attr->is_inline + attr->is_tls > 1)
error_tok(tok, "typedef may not be used together with static,"
" extern, inline, __thread or _Thread_local");
tok = tok->next;
continue;
}
// These keywords are recognized but ignored.
if (consume(&tok, tok, "const") || consume(&tok, tok, "volatile") ||
consume(&tok, tok, "auto") || consume(&tok, tok, "register") ||
consume(&tok, tok, "restrict") || consume(&tok, tok, "__restrict") ||
consume(&tok, tok, "__restrict__") || consume(&tok, tok, "_Noreturn"))
continue;
if (equal(tok, "_Alignas")) {
if (!attr)
error_tok(tok, "_Alignas is not allowed in this context");
tok = skip(tok->next, "(");
if (is_typename(tok))
attr->align = typename(&tok, tok)->align;
else
attr->align = const_expr(&tok, tok);
tok = skip(tok, ")");
continue;
}
// Handle user-defined types.
Type *ty2 = find_typedef(tok);
if (equal(tok, "struct") || equal(tok, "union") || equal(tok, "enum") ||
equal(tok, "typeof") || ty2) {
if (counter)
break;
if (equal(tok, "struct")) {
ty = struct_decl(&tok, tok->next);
} else if (equal(tok, "union")) {
ty = union_decl(&tok, tok->next);
} else if (equal(tok, "enum")) {
ty = enum_specifier(&tok, tok->next);
} else if (equal(tok, "typeof")) {
ty = typeof_specifier(&tok, tok->next);
} else {
ty = ty2;
tok = tok->next;
}
counter += OTHER;
continue;
}
// Handle built-in types.
if (equal(tok, "void"))
counter += VOID;
else if (equal(tok, "_Bool"))
counter += BOOL;
else if (equal(tok, "char"))
counter += CHAR;
else if (equal(tok, "short"))
counter += SHORT;
else if (equal(tok, "int"))
counter += INT;
else if (equal(tok, "long"))
counter += LONG;
else if (equal(tok, "float"))
counter += FLOAT;
else if (equal(tok, "double"))
counter += DOUBLE;
else if (equal(tok, "signed"))
counter |= SIGNED;
else if (equal(tok, "unsigned"))
counter |= UNSIGNED;
else
unreachable();
switch (counter) {
case VOID:
ty = ty_void;
break;
case BOOL:
ty = ty_bool;
break;
case CHAR:
case SIGNED + CHAR:
ty = ty_char;
break;
case UNSIGNED + CHAR:
ty = ty_uchar;
break;
case SHORT:
case SHORT + INT:
case SIGNED + SHORT:
case SIGNED + SHORT + INT:
ty = ty_short;
break;
case UNSIGNED + SHORT:
case UNSIGNED + SHORT + INT:
ty = ty_ushort;
break;
case INT:
case SIGNED:
case SIGNED + INT:
ty = ty_int;
break;
case UNSIGNED:
case UNSIGNED + INT:
ty = ty_uint;
break;
case LONG:
case LONG + INT:
case LONG + LONG:
case LONG + LONG + INT:
case SIGNED + LONG:
case SIGNED + LONG + INT:
case SIGNED + LONG + LONG:
case SIGNED + LONG + LONG + INT:
ty = ty_long;
break;
case UNSIGNED + LONG:
case UNSIGNED + LONG + INT:
case UNSIGNED + LONG + LONG:
case UNSIGNED + LONG + LONG + INT:
ty = ty_ulong;
break;
case FLOAT:
ty = ty_float;
break;
case DOUBLE:
ty = ty_double;
break;
case LONG + DOUBLE:
ty = ty_ldouble;
break;
default:
error_tok(tok, "invalid type");
}
tok = tok->next;
}
*rest = tok;
return ty;
}
// func-params = ("void" | param ("," param)* ("," "...")?)? ")"
// param = declspec declarator
static Type *func_params(Token **rest, Token *tok, Type *ty) {
if (equal(tok, "void") && equal(tok->next, ")")) {
*rest = tok->next->next;
return func_type(ty);
}
Type head = {};
Type *cur = &head;
bool is_variadic = false;
while (!equal(tok, ")")) {
if (cur != &head)
tok = skip(tok, ",");
if (equal(tok, "...")) {
is_variadic = true;
tok = tok->next;
skip(tok, ")");
break;
}
Type *ty2 = declspec(&tok, tok, NULL);
ty2 = declarator(&tok, tok, ty2);
Token *name = ty2->name;
if (ty2->kind == TY_ARRAY) {
// "array of T" is converted to "pointer to T" only in the parameter
// context. For example, *argv[] is converted to **argv by this.
ty2 = pointer_to(ty2->base);
ty2->name = name;
} else if (ty2->kind == TY_FUNC) {
// Likewise, a function is converted to a pointer to a function
// only in the parameter context.
ty2 = pointer_to(ty2);
ty2->name = name;
}
cur = cur->next = copy_type(ty2);
}
if (cur == &head)
is_variadic = true;
ty = func_type(ty);
ty->params = head.next;
ty->is_variadic = is_variadic;
*rest = tok->next;
return ty;
}
// array-dimensions = ("static" | "restrict")* const-expr? "]" type-suffix
static Type *array_dimensions(Token **rest, Token *tok, Type *ty) {
while (equal(tok, "static") || equal(tok, "restrict"))
tok = tok->next;
if (equal(tok, "]")) {
ty = type_suffix(rest, tok->next, ty);
return array_of(ty, -1);
}
Node *expr = conditional(&tok, tok);
tok = skip(tok, "]");
ty = type_suffix(rest, tok, ty);
if (ty->kind == TY_VLA || !is_const_expr(expr))
return vla_of(ty, expr);
return array_of(ty, eval(expr));
}
// type-suffix = "(" func-params
// | "[" array-dimensions
// | ε
static Type *type_suffix(Token **rest, Token *tok, Type *ty) {
if (equal(tok, "("))
return func_params(rest, tok->next, ty);
if (equal(tok, "["))
return array_dimensions(rest, tok->next, ty);
*rest = tok;
return ty;
}
// pointers = ("*" ("const" | "volatile" | "restrict")*)*
static Type *pointers(Token **rest, Token *tok, Type *ty) {
while (consume(&tok, tok, "*")) {
ty = pointer_to(ty);
while (equal(tok, "const") || equal(tok, "volatile") || equal(tok, "restrict") ||
equal(tok, "__restrict") || equal(tok, "__restrict__"))
tok = tok->next;
}
*rest = tok;
return ty;
}
// declarator = pointers ("(" ident ")" | "(" declarator ")" | ident) type-suffix
static Type *declarator(Token **rest, Token *tok, Type *ty) {
ty = pointers(&tok, tok, ty);
if (equal(tok, "(")) {
Token *start = tok;
Type dummy = {};
declarator(&tok, start->next, &dummy);
tok = skip(tok, ")");
ty = type_suffix(rest, tok, ty);
return declarator(&tok, start->next, ty);
}
Token *name = NULL;
Token *name_pos = tok;
if (tok->kind == TK_IDENT) {
name = tok;
tok = tok->next;
}
ty = type_suffix(rest, tok, ty);
ty->name = name;
ty->name_pos = name_pos;
return ty;
}
// abstract-declarator = pointers ("(" abstract-declarator ")")? type-suffix
static Type *abstract_declarator(Token **rest, Token *tok, Type *ty) {
ty = pointers(&tok, tok, ty);
if (equal(tok, "(")) {
Token *start = tok;
Type dummy = {};
abstract_declarator(&tok, start->next, &dummy);
tok = skip(tok, ")");
ty = type_suffix(rest, tok, ty);
return abstract_declarator(&tok, start->next, ty);
}
return type_suffix(rest, tok, ty);
}
// type-name = declspec abstract-declarator
static Type *typename(Token **rest, Token *tok) {
Type *ty = declspec(&tok, tok, NULL);
return abstract_declarator(rest, tok, ty);
}
static bool is_end(Token *tok) {
return equal(tok, "}") || (equal(tok, ",") && equal(tok->next, "}"));
}
static bool consume_end(Token **rest, Token *tok) {
if (equal(tok, "}")) {
*rest = tok->next;
return true;
}
if (equal(tok, ",") && equal(tok->next, "}")) {
*rest = tok->next->next;
return true;
}
return false;
}
// enum-specifier = ident? "{" enum-list? "}"
// | ident ("{" enum-list? "}")?
//
// enum-list = ident ("=" num)? ("," ident ("=" num)?)* ","?
static Type *enum_specifier(Token **rest, Token *tok) {
Type *ty = enum_type();
// Read a struct tag.
Token *tag = NULL;
if (tok->kind == TK_IDENT) {
tag = tok;
tok = tok->next;
}
if (tag && !equal(tok, "{")) {
Type *ty = find_tag(tag);
if (!ty)
error_tok(tag, "unknown enum type");
if (ty->kind != TY_ENUM)
error_tok(tag, "not an enum tag");
*rest = tok;
return ty;
}
tok = skip(tok, "{");
// Read an enum-list.
int i = 0;
int val = 0;
while (!consume_end(rest, tok)) {
if (i++ > 0)
tok = skip(tok, ",");
char *name = get_ident(tok);
tok = tok->next;
if (equal(tok, "="))
val = const_expr(&tok, tok->next);
VarScope *sc = push_scope(name);
sc->enum_ty = ty;
sc->enum_val = val++;
}
if (tag)
push_tag_scope(tag, ty);
return ty;
}
// typeof-specifier = "(" (expr | typename) ")"
static Type *typeof_specifier(Token **rest, Token *tok) {
tok = skip(tok, "(");
Type *ty;
if (is_typename(tok)) {
ty = typename(&tok, tok);
} else {
Node *node = expr(&tok, tok);
add_type(node);
ty = node->ty;
}
*rest = skip(tok, ")");
return ty;
}
// Generate code for computing a VLA size.
static Node *compute_vla_size(Type *ty, Token *tok) {
Node *node = new_node(ND_NULL_EXPR, tok);
if (ty->base)
node = new_binary(ND_COMMA, node, compute_vla_size(ty->base, tok), tok);
if (ty->kind != TY_VLA)
return node;
Node *base_sz;
if (ty->base->kind == TY_VLA)
base_sz = new_var_node(ty->base->vla_size, tok);
else
base_sz = new_num(ty->base->size, tok);
ty->vla_size = new_lvar("", ty_ulong);
Node *expr = new_binary(ND_ASSIGN, new_var_node(ty->vla_size, tok),
new_binary(ND_MUL, ty->vla_len, base_sz, tok),
tok);
return new_binary(ND_COMMA, node, expr, tok);
}
static Node *new_alloca(Node *sz) {
Node *node = new_unary(ND_FUNCALL, new_var_node(builtin_alloca, sz->tok), sz->tok);
node->func_ty = builtin_alloca->ty;
node->ty = builtin_alloca->ty->return_ty;
node->args = sz;
add_type(sz);
return node;
}
// declaration = declspec (declarator ("=" expr)? ("," declarator ("=" expr)?)*)? ";"
static Node *declaration(Token **rest, Token *tok, Type *basety, VarAttr *attr) {
Node head = {};
Node *cur = &head;
int i = 0;
while (!equal(tok, ";")) {
if (i++ > 0)
tok = skip(tok, ",");
Type *ty = declarator(&tok, tok, basety);
if (ty->kind == TY_VOID)
error_tok(tok, "variable declared void");
if (!ty->name)
error_tok(ty->name_pos, "variable name omitted");
if (attr && attr->is_static) {
// static local variable
Obj *var = new_anon_gvar(ty);
push_scope(get_ident(ty->name))->var = var;
if (equal(tok, "="))
gvar_initializer(&tok, tok->next, var);
continue;
}
// Generate code for computing a VLA size. We need to do this
// even if ty is not VLA because ty may be a pointer to VLA
// (e.g. int (*foo)[n][m] where n and m are variables.)
cur = cur->next = new_unary(ND_EXPR_STMT, compute_vla_size(ty, tok), tok);
if (ty->kind == TY_VLA) {
if (equal(tok, "="))
error_tok(tok, "variable-sized object may not be initialized");
// Variable length arrays (VLAs) are translated to alloca() calls.
// For example, `int x[n+2]` is translated to `tmp = n + 2,
// x = alloca(tmp)`.
Obj *var = new_lvar(get_ident(ty->name), ty);
Token *tok = ty->name;
Node *expr = new_binary(ND_ASSIGN, new_vla_ptr(var, tok),
new_alloca(new_var_node(ty->vla_size, tok)),
tok);
cur = cur->next = new_unary(ND_EXPR_STMT, expr, tok);
continue;
}
Obj *var = new_lvar(get_ident(ty->name), ty);
if (attr && attr->align)
var->align = attr->align;
if (equal(tok, "=")) {
Node *expr = lvar_initializer(&tok, tok->next, var);
cur = cur->next = new_unary(ND_EXPR_STMT, expr, tok);
}
if (var->ty->size < 0)
error_tok(ty->name, "variable has incomplete type");
if (var->ty->kind == TY_VOID)
error_tok(ty->name, "variable declared void");
}
Node *node = new_node(ND_BLOCK, tok);
node->body = head.next;
*rest = tok->next;
return node;
}
static Token *skip_excess_element(Token *tok) {
if (equal(tok, "{")) {
tok = skip_excess_element(tok->next);
return skip(tok, "}");
}
assign(&tok, tok);
return tok;
}
// string-initializer = string-literal
static void string_initializer(Token **rest, Token *tok, Initializer *init) {
if (init->is_flexible)
*init = *new_initializer(array_of(init->ty->base, tok->ty->array_len), false);
int len = MIN(init->ty->array_len, tok->ty->array_len);
switch (init->ty->base->size) {
case 1: {
char *str = tok->str;
for (int i = 0; i < len; i++)
init->children[i]->expr = new_num(str[i], tok);
break;
}
case 2: {
uint16_t *str = (uint16_t *)tok->str;
for (int i = 0; i < len; i++)
init->children[i]->expr = new_num(str[i], tok);
break;
}
case 4: {
uint32_t *str = (uint32_t *)tok->str;
for (int i = 0; i < len; i++)
init->children[i]->expr = new_num(str[i], tok);
break;
}
default:
unreachable();
}
*rest = tok->next;
}
// array-designator = "[" const-expr "]"
//
// C99 added the designated initializer to the language, which allows
// programmers to move the "cursor" of an initializer to any element.
// The syntax looks like this:
//
// int x[10] = { 1, 2, [5]=3, 4, 5, 6, 7 };
//
// `[5]` moves the cursor to the 5th element, so the 5th element of x
// is set to 3. Initialization then continues forward in order, so
// 6th, 7th, 8th and 9th elements are initialized with 4, 5, 6 and 7,
// respectively. Unspecified elements (in this case, 3rd and 4th
// elements) are initialized with zero.
//
// Nesting is allowed, so the following initializer is valid:
//
// int x[5][10] = { [5][8]=1, 2, 3 };
//
// It sets x[5][8], x[5][9] and x[6][0] to 1, 2 and 3, respectively.
//
// Use `.fieldname` to move the cursor for a struct initializer. E.g.
//
// struct { int a, b, c; } x = { .c=5 };
//
// The above initializer sets x.c to 5.
static void array_designator(Token **rest, Token *tok, Type *ty, int *begin, int *end) {
*begin = const_expr(&tok, tok->next);
if (*begin >= ty->array_len)
error_tok(tok, "array designator index exceeds array bounds");
if (equal(tok, "...")) {
*end = const_expr(&tok, tok->next);
if (*end >= ty->array_len)
error_tok(tok, "array designator index exceeds array bounds");
if (*end < *begin)
error_tok(tok, "array designator range [%d, %d] is empty", *begin, *end);
} else {
*end = *begin;
}
*rest = skip(tok, "]");
}
// struct-designator = "." ident
static Member *struct_designator(Token **rest, Token *tok, Type *ty) {
Token *start = tok;
tok = skip(tok, ".");
if (tok->kind != TK_IDENT)
error_tok(tok, "expected a field designator");
for (Member *mem = ty->members; mem; mem = mem->next) {
// Anonymous struct member
if (mem->ty->kind == TY_STRUCT && !mem->name) {
if (get_struct_member(mem->ty, tok)) {
*rest = start;
return mem;
}
continue;
}
// Regular struct member
if (mem->name->len == tok->len && !strncmp(mem->name->loc, tok->loc, tok->len)) {
*rest = tok->next;
return mem;
}
}
error_tok(tok, "struct has no such member");
}
// designation = ("[" const-expr "]" | "." ident)* "="? initializer
static void designation(Token **rest, Token *tok, Initializer *init) {
if (equal(tok, "[")) {
if (init->ty->kind != TY_ARRAY)
error_tok(tok, "array index in non-array initializer");
int begin, end;
array_designator(&tok, tok, init->ty, &begin, &end);
Token *tok2;
for (int i = begin; i <= end; i++)
designation(&tok2, tok, init->children[i]);
array_initializer2(rest, tok2, init, begin + 1);
return;
}
if (equal(tok, ".") && init->ty->kind == TY_STRUCT) {
Member *mem = struct_designator(&tok, tok, init->ty);
designation(&tok, tok, init->children[mem->idx]);
init->expr = NULL;
struct_initializer2(rest, tok, init, mem->next);
return;
}
if (equal(tok, ".") && init->ty->kind == TY_UNION) {
Member *mem = struct_designator(&tok, tok, init->ty);
init->mem = mem;
designation(rest, tok, init->children[mem->idx]);
return;
}
if (equal(tok, "."))
error_tok(tok, "field name not in struct or union initializer");
if (equal(tok, "="))
tok = tok->next;
initializer2(rest, tok, init);
}
// An array length can be omitted if an array has an initializer
// (e.g. `int x[] = {1,2,3}`). If it's omitted, count the number
// of initializer elements.
static int count_array_init_elements(Token *tok, Type *ty) {
bool first = true;
Initializer *dummy = new_initializer(ty->base, true);
int i = 0, max = 0;
while (!consume_end(&tok, tok)) {
if (!first)
tok = skip(tok, ",");
first = false;
if (equal(tok, "[")) {
i = const_expr(&tok, tok->next);
if (equal(tok, "..."))
i = const_expr(&tok, tok->next);
tok = skip(tok, "]");
designation(&tok, tok, dummy);
} else {
initializer2(&tok, tok, dummy);
}
i++;
max = MAX(max, i);
}
return max;
}
// array-initializer1 = "{" initializer ("," initializer)* ","? "}"
static void array_initializer1(Token **rest, Token *tok, Initializer *init) {
tok = skip(tok, "{");
if (init->is_flexible) {
int len = count_array_init_elements(tok, init->ty);
*init = *new_initializer(array_of(init->ty->base, len), false);
}
bool first = true;
if (init->is_flexible) {
int len = count_array_init_elements(tok, init->ty);
*init = *new_initializer(array_of(init->ty->base, len), false);
}
for (int i = 0; !consume_end(rest, tok); i++) {
if (!first)
tok = skip(tok, ",");
first = false;
if (equal(tok, "[")) {
int begin, end;
array_designator(&tok, tok, init->ty, &begin, &end);
Token *tok2;
for (int j = begin; j <= end; j++)
designation(&tok2, tok, init->children[j]);
tok = tok2;
i = end;
continue;
}
if (i < init->ty->array_len)
initializer2(&tok, tok, init->children[i]);
else
tok = skip_excess_element(tok);
}
}
// array-initializer2 = initializer ("," initializer)*
static void array_initializer2(Token **rest, Token *tok, Initializer *init, int i) {
if (init->is_flexible) {
int len = count_array_init_elements(tok, init->ty);
*init = *new_initializer(array_of(init->ty->base, len), false);
}
for (; i < init->ty->array_len && !is_end(tok); i++) {
Token *start = tok;
if (i > 0)
tok = skip(tok, ",");
if (equal(tok, "[") || equal(tok, ".")) {
*rest = start;
return;
}
initializer2(&tok, tok, init->children[i]);
}
*rest = tok;
}
// struct-initializer1 = "{" initializer ("," initializer)* ","? "}"
static void struct_initializer1(Token **rest, Token *tok, Initializer *init) {
tok = skip(tok, "{");
Member *mem = init->ty->members;
bool first = true;
while (!consume_end(rest, tok)) {
if (!first)
tok = skip(tok, ",");
first = false;
if (equal(tok, ".")) {
mem = struct_designator(&tok, tok, init->ty);
designation(&tok, tok, init->children[mem->idx]);
mem = mem->next;
continue;
}
if (mem) {
initializer2(&tok, tok, init->children[mem->idx]);
mem = mem->next;
} else {
tok = skip_excess_element(tok);
}
}
}
// struct-initializer2 = initializer ("," initializer)*
static void struct_initializer2(Token **rest, Token *tok, Initializer *init, Member *mem) {
bool first = true;
for (; mem && !is_end(tok); mem = mem->next) {
Token *start = tok;
if (!first)
tok = skip(tok, ",");
first = false;
if (equal(tok, "[") || equal(tok, ".")) {
*rest = start;
return;
}
initializer2(&tok, tok, init->children[mem->idx]);
}
*rest = tok;
}
static void union_initializer(Token **rest, Token *tok, Initializer *init) {
// Unlike structs, union initializers take only one initializer,
// and that initializes the first union member by default.
// You can initialize other member using a designated initializer.
if (equal(tok, "{") && equal(tok->next, ".")) {
Member *mem = struct_designator(&tok, tok->next, init->ty);
init->mem = mem;
designation(&tok, tok, init->children[mem->idx]);
*rest = skip(tok, "}");
return;
}
init->mem = init->ty->members;
if (equal(tok, "{")) {
initializer2(&tok, tok->next, init->children[0]);
consume(&tok, tok, ",");
*rest = skip(tok, "}");
} else {
initializer2(rest, tok, init->children[0]);
}
}
// initializer = string-initializer | array-initializer
// | struct-initializer | union-initializer
// | assign
static void initializer2(Token **rest, Token *tok, Initializer *init) {
if (init->ty->kind == TY_ARRAY && tok->kind == TK_STR) {
string_initializer(rest, tok, init);
return;
}
if (init->ty->kind == TY_ARRAY) {
if (equal(tok, "{"))
array_initializer1(rest, tok, init);
else
array_initializer2(rest, tok, init, 0);
return;
}
if (init->ty->kind == TY_STRUCT) {
if (equal(tok, "{")) {
struct_initializer1(rest, tok, init);
return;
}
// A struct can be initialized with another struct. E.g.
// `struct T x = y;` where y is a variable of type `struct T`.
// Handle that case first.
Node *expr = assign(rest, tok);
add_type(expr);
if (expr->ty->kind == TY_STRUCT) {
init->expr = expr;
return;
}
struct_initializer2(rest, tok, init, init->ty->members);
return;
}
if (init->ty->kind == TY_UNION) {
union_initializer(rest, tok, init);
return;
}
if (equal(tok, "{")) {
// An initializer for a scalar variable can be surrounded by
// braces. E.g. `int x = {3};`. Handle that case.
initializer2(&tok, tok->next, init);
*rest = skip(tok, "}");
return;
}
init->expr = assign(rest, tok);
}
static Type *copy_struct_type(Type *ty) {
ty = copy_type(ty);
Member head = {};
Member *cur = &head;
for (Member *mem = ty->members; mem; mem = mem->next) {
Member *m = calloc(1, sizeof(Member));
*m = *mem;
cur = cur->next = m;
}
ty->members = head.next;
return ty;
}
static Initializer *initializer(Token **rest, Token *tok, Type *ty, Type **new_ty) {
Initializer *init = new_initializer(ty, true);
initializer2(rest, tok, init);
if ((ty->kind == TY_STRUCT || ty->kind == TY_UNION) && ty->is_flexible) {
ty = copy_struct_type(ty);
Member *mem = ty->members;
while (mem->next)
mem = mem->next;
mem->ty = init->children[mem->idx]->ty;
ty->size += mem->ty->size;
*new_ty = ty;
return init;
}
*new_ty = init->ty;
return init;
}
static Node *init_desg_expr(InitDesg *desg, Token *tok) {
if (desg->var)
return new_var_node(desg->var, tok);
if (desg->member) {
Node *node = new_unary(ND_MEMBER, init_desg_expr(desg->next, tok), tok);
node->member = desg->member;
return node;
}
Node *lhs = init_desg_expr(desg->next, tok);
Node *rhs = new_num(desg->idx, tok);
return new_unary(ND_DEREF, new_add(lhs, rhs, tok), tok);
}
static Node *create_lvar_init(Initializer *init, Type *ty, InitDesg *desg, Token *tok) {
if (ty->kind == TY_ARRAY) {
Node *node = new_node(ND_NULL_EXPR, tok);
for (int i = 0; i < ty->array_len; i++) {
InitDesg desg2 = {desg, i};
Node *rhs = create_lvar_init(init->children[i], ty->base, &desg2, tok);
node = new_binary(ND_COMMA, node, rhs, tok);
}
return node;
}
if (ty->kind == TY_STRUCT && !init->expr) {
Node *node = new_node(ND_NULL_EXPR, tok);
for (Member *mem = ty->members; mem; mem = mem->next) {
InitDesg desg2 = {desg, 0, mem};
Node *rhs = create_lvar_init(init->children[mem->idx], mem->ty, &desg2, tok);
node = new_binary(ND_COMMA, node, rhs, tok);
}
return node;
}
if (ty->kind == TY_UNION) {
Member *mem = init->mem ? init->mem : ty->members;
InitDesg desg2 = {desg, 0, mem};
return create_lvar_init(init->children[mem->idx], mem->ty, &desg2, tok);
}
if (!init->expr)
return new_node(ND_NULL_EXPR, tok);
Node *lhs = init_desg_expr(desg, tok);
return new_binary(ND_ASSIGN, lhs, init->expr, tok);
}
// A variable definition with an initializer is a shorthand notation
// for a variable definition followed by assignments. This function
// generates assignment expressions for an initializer. For example,
// `int x[2][2] = {{6, 7}, {8, 9}}` is converted to the following
// expressions:
//
// x[0][0] = 6;
// x[0][1] = 7;
// x[1][0] = 8;
// x[1][1] = 9;
static Node *lvar_initializer(Token **rest, Token *tok, Obj *var) {
Initializer *init = initializer(rest, tok, var->ty, &var->ty);
InitDesg desg = {NULL, 0, NULL, var};
// If a partial initializer list is given, the standard requires
// that unspecified elements are set to 0. Here, we simply
// zero-initialize the entire memory region of a variable before
// initializing it with user-supplied values.
Node *lhs = new_node(ND_MEMZERO, tok);
lhs->var = var;
Node *rhs = create_lvar_init(init, var->ty, &desg, tok);
return new_binary(ND_COMMA, lhs, rhs, tok);
}
static uint64_t read_buf(char *buf, int sz) {
if (sz == 1)
return *buf;
if (sz == 2)
return *(uint16_t *)buf;
if (sz == 4)
return *(uint32_t *)buf;
if (sz == 8)
return *(uint64_t *)buf;
unreachable();
}
static void write_buf(char *buf, uint64_t val, int sz) {
if (sz == 1)
*buf = val;
else if (sz == 2)
*(uint16_t *)buf = val;
else if (sz == 4)
*(uint32_t *)buf = val;
else if (sz == 8)
*(uint64_t *)buf = val;
else
unreachable();
}
static Relocation *
write_gvar_data(Relocation *cur, Initializer *init, Type *ty, char *buf, int offset) {
if (ty->kind == TY_ARRAY) {
int sz = ty->base->size;
for (int i = 0; i < ty->array_len; i++)
cur = write_gvar_data(cur, init->children[i], ty->base, buf, offset + sz * i);
return cur;
}
if (ty->kind == TY_STRUCT) {
for (Member *mem = ty->members; mem; mem = mem->next) {
if (mem->is_bitfield) {
Node *expr = init->children[mem->idx]->expr;
if (!expr)
break;
char *loc = buf + offset + mem->offset;
uint64_t oldval = read_buf(loc, mem->ty->size);
uint64_t newval = eval(expr);
uint64_t mask = (1L << mem->bit_width) - 1;
uint64_t combined = oldval | ((newval & mask) << mem->bit_offset);
write_buf(loc, combined, mem->ty->size);
} else {
cur = write_gvar_data(cur, init->children[mem->idx], mem->ty, buf,
offset + mem->offset);
}
}
return cur;
}
if (ty->kind == TY_UNION) {
if (!init->mem)
return cur;
return write_gvar_data(cur, init->children[init->mem->idx],
init->mem->ty, buf, offset);
}
if (!init->expr)
return cur;
if (ty->kind == TY_FLOAT) {
*(float *)(buf + offset) = eval_double(init->expr);
return cur;
}
if (ty->kind == TY_DOUBLE) {
*(double *)(buf + offset) = eval_double(init->expr);
return cur;
}
char *label = NULL;
uint64_t val = eval2(init->expr, &label);
if (!label) {
write_buf(buf + offset, val, ty->size);
return cur;
}
Relocation *rel = calloc(1, sizeof(Relocation));
rel->offset = offset;
rel->label = label;
rel->addend = val;
cur->next = rel;
return cur->next;
}
// Initializers for global variables are evaluated at compile-time and
// embedded to .data section. This function serializes Initializer
// objects to a flat byte array. It is a compile error if an
// initializer list contains a non-constant expression.
static void gvar_initializer(Token **rest, Token *tok, Obj *var) {
Initializer *init = initializer(rest, tok, var->ty, &var->ty);
Relocation head = {};
char *buf = calloc(1, var->ty->size);
write_gvar_data(&head, init, var->ty, buf, 0);
var->init_data = buf;
var->rel = head.next;
}
// Returns true if a given token represents a type.
static bool is_typename(Token *tok) {
static char *kw[] = {
"void", "_Bool", "char", "short", "int", "long", "struct", "union",
"typedef", "enum", "static", "extern", "_Alignas", "signed", "unsigned",
"const", "volatile", "auto", "register", "restrict", "__restrict",
"__restrict__", "_Noreturn", "float", "double", "typeof", "inline",
"_Thread_local", "__thread",
};
for (int i = 0; i < sizeof(kw) / sizeof(*kw); i++)
if (equal(tok, kw[i]))
return true;
return find_typedef(tok);
}
// asm-stmt = "asm" ("volatile" | "inline")* "(" string-literal ")"
static Node *asm_stmt(Token **rest, Token *tok) {
Node *node = new_node(ND_ASM, tok);
tok = tok->next;
while (equal(tok, "volatile") || equal(tok, "inline"))
tok = tok->next;
tok = skip(tok, "(");
if (tok->kind != TK_STR || tok->ty->base->kind != TY_CHAR)
error_tok(tok, "expected string literal");
node->asm_str = tok->str;
*rest = skip(tok->next, ")");
return node;
}
// stmt = "return" expr? ";"
// | "if" "(" expr ")" stmt ("else" stmt)?
// | "switch" "(" expr ")" stmt
// | "case" const-expr ("..." const-expr)? ":" stmt
// | "default" ":" stmt
// | "for" "(" expr-stmt expr? ";" expr? ")" stmt
// | "while" "(" expr ")" stmt
// | "do" stmt "while" "(" expr ")" ";"
// | "asm" asm-stmt
// | "goto" (ident | "*" expr) ";"
// | "break" ";"
// | "continue" ";"
// | ident ":" stmt
// | "{" compound-stmt
// | expr-stmt
static Node *stmt(Token **rest, Token *tok) {
if (equal(tok, "return")) {
Node *node = new_node(ND_RETURN, tok);
if (consume(rest, tok->next, ";"))
return node;
Node *exp = expr(&tok, tok->next);
*rest = skip(tok, ";");
add_type(exp);
Type *ty = current_fn->ty->return_ty;
if (ty->kind != TY_STRUCT && ty->kind != TY_UNION)
exp = new_cast(exp, current_fn->ty->return_ty);
node->lhs = exp;
return node;
}
if (equal(tok, "if")) {
Node *node = new_node(ND_IF, tok);
tok = skip(tok->next, "(");
node->cond = expr(&tok, tok);
tok = skip(tok, ")");
node->then = stmt(&tok, tok);
if (equal(tok, "else"))
node->els = stmt(&tok, tok->next);
*rest = tok;
return node;
}
if (equal(tok, "switch")) {
Node *node = new_node(ND_SWITCH, tok);
tok = skip(tok->next, "(");
node->cond = expr(&tok, tok);
tok = skip(tok, ")");
Node *sw = current_switch;
current_switch = node;
char *brk = brk_label;
brk_label = node->brk_label = new_unique_name();
node->then = stmt(rest, tok);
current_switch = sw;
brk_label = brk;
return node;
}
if (equal(tok, "case")) {
if (!current_switch)
error_tok(tok, "stray case");
Node *node = new_node(ND_CASE, tok);
int begin = const_expr(&tok, tok->next);
int end;
if (equal(tok, "...")) {
// [GNU] Case ranges, e.g. "case 1 ... 5:"
end = const_expr(&tok, tok->next);
if (end < begin)
error_tok(tok, "empty case range specified");
} else {
end = begin;
}
tok = skip(tok, ":");
node->label = new_unique_name();
node->lhs = stmt(rest, tok);
node->begin = begin;
node->end = end;
node->case_next = current_switch->case_next;
current_switch->case_next = node;
return node;
}
if (equal(tok, "default")) {
if (!current_switch)
error_tok(tok, "stray default");
Node *node = new_node(ND_CASE, tok);
tok = skip(tok->next, ":");
node->label = new_unique_name();
node->lhs = stmt(rest, tok);
current_switch->default_case = node;
return node;
}
if (equal(tok, "for")) {
Node *node = new_node(ND_FOR, tok);
tok = skip(tok->next, "(");
enter_scope();
char *brk = brk_label;
char *cont = cont_label;
brk_label = node->brk_label = new_unique_name();
cont_label = node->cont_label = new_unique_name();
if (is_typename(tok)) {
Type *basety = declspec(&tok, tok, NULL);
node->init = declaration(&tok, tok, basety, NULL);
} else {
node->init = expr_stmt(&tok, tok);
}
if (!equal(tok, ";"))
node->cond = expr(&tok, tok);
tok = skip(tok, ";");
if (!equal(tok, ")"))
node->inc = expr(&tok, tok);
tok = skip(tok, ")");
node->then = stmt(rest, tok);
leave_scope();
brk_label = brk;
cont_label = cont;
return node;
}
if (equal(tok, "while")) {
Node *node = new_node(ND_FOR, tok);
tok = skip(tok->next, "(");
node->cond = expr(&tok, tok);
tok = skip(tok, ")");
char *brk = brk_label;
char *cont = cont_label;
brk_label = node->brk_label = new_unique_name();
cont_label = node->cont_label = new_unique_name();
node->then = stmt(rest, tok);
brk_label = brk;
cont_label = cont;
return node;
}
if (equal(tok, "do")) {
Node *node = new_node(ND_DO, tok);
char *brk = brk_label;
char *cont = cont_label;
brk_label = node->brk_label = new_unique_name();
cont_label = node->cont_label = new_unique_name();
node->then = stmt(&tok, tok->next);
brk_label = brk;
cont_label = cont;
tok = skip(tok, "while");
tok = skip(tok, "(");
node->cond = expr(&tok, tok);
tok = skip(tok, ")");
*rest = skip(tok, ";");
return node;
}
if (equal(tok, "asm"))
return asm_stmt(rest, tok);
if (equal(tok, "goto")) {
if (equal(tok->next, "*")) {
// [GNU] `goto *ptr` jumps to the address specified by `ptr`.
Node *node = new_node(ND_GOTO_EXPR, tok);
node->lhs = expr(&tok, tok->next->next);
*rest = skip(tok, ";");
return node;
}
Node *node = new_node(ND_GOTO, tok);
node->label = get_ident(tok->next);
node->goto_next = gotos;
gotos = node;
*rest = skip(tok->next->next, ";");
return node;
}
if (equal(tok, "break")) {
if (!brk_label)
error_tok(tok, "stray break");
Node *node = new_node(ND_GOTO, tok);
node->unique_label = brk_label;
*rest = skip(tok->next, ";");
return node;
}
if (equal(tok, "continue")) {
if (!cont_label)
error_tok(tok, "stray continue");
Node *node = new_node(ND_GOTO, tok);
node->unique_label = cont_label;
*rest = skip(tok->next, ";");
return node;
}
if (tok->kind == TK_IDENT && equal(tok->next, ":")) {
Node *node = new_node(ND_LABEL, tok);
node->label = strndup(tok->loc, tok->len);
node->unique_label = new_unique_name();
node->lhs = stmt(rest, tok->next->next);
node->goto_next = labels;
labels = node;
return node;
}
if (equal(tok, "{"))
return compound_stmt(rest, tok->next);
return expr_stmt(rest, tok);
}
// compound-stmt = (typedef | declaration | stmt)* "}"
static Node *compound_stmt(Token **rest, Token *tok) {
Node *node = new_node(ND_BLOCK, tok);
Node head = {};
Node *cur = &head;
enter_scope();
while (!equal(tok, "}")) {
if (is_typename(tok) && !equal(tok->next, ":")) {
VarAttr attr = {};
Type *basety = declspec(&tok, tok, &attr);
if (attr.is_typedef) {
tok = parse_typedef(tok, basety);
continue;
}
if (is_function(tok)) {
tok = function(tok, basety, &attr);
continue;
}
if (attr.is_extern) {
tok = global_variable(tok, basety, &attr);
continue;
}
cur = cur->next = declaration(&tok, tok, basety, &attr);
} else {
cur = cur->next = stmt(&tok, tok);
}
add_type(cur);
}
leave_scope();
node->body = head.next;
*rest = tok->next;
return node;
}
// expr-stmt = expr? ";"
static Node *expr_stmt(Token **rest, Token *tok) {
if (equal(tok, ";")) {
*rest = tok->next;
return new_node(ND_BLOCK, tok);
}
Node *node = new_node(ND_EXPR_STMT, tok);
node->lhs = expr(&tok, tok);
*rest = skip(tok, ";");
return node;
}
// expr = assign ("," expr)?
static Node *expr(Token **rest, Token *tok) {
Node *node = assign(&tok, tok);
if (equal(tok, ","))
return new_binary(ND_COMMA, node, expr(rest, tok->next), tok);
*rest = tok;
return node;
}
static int64_t eval(Node *node) {
return eval2(node, NULL);
}
// Evaluate a given node as a constant expression.
//
// A constant expression is either just a number or ptr+n where ptr
// is a pointer to a global variable and n is a postiive/negative
// number. The latter form is accepted only as an initialization
// expression for a global variable.
static int64_t eval2(Node *node, char **label) {
add_type(node);
if (is_flonum(node->ty))
return eval_double(node);
switch (node->kind) {
case ND_ADD:
return eval2(node->lhs, label) + eval(node->rhs);
case ND_SUB:
return eval2(node->lhs, label) - eval(node->rhs);
case ND_MUL:
return eval(node->lhs) * eval(node->rhs);
case ND_DIV:
if (node->ty->is_unsigned)
return (uint64_t)eval(node->lhs) / eval(node->rhs);
return eval(node->lhs) / eval(node->rhs);
case ND_NEG:
return -eval(node->lhs);
case ND_MOD:
if (node->ty->is_unsigned)
return (uint64_t)eval(node->lhs) % eval(node->rhs);
return eval(node->lhs) % eval(node->rhs);
case ND_BITAND:
return eval(node->lhs) & eval(node->rhs);
case ND_BITOR:
return eval(node->lhs) | eval(node->rhs);
case ND_BITXOR:
return eval(node->lhs) ^ eval(node->rhs);
case ND_SHL:
return eval(node->lhs) << eval(node->rhs);
case ND_SHR:
if (node->ty->is_unsigned && node->ty->size == 8)
return (uint64_t)eval(node->lhs) >> eval(node->rhs);
return eval(node->lhs) >> eval(node->rhs);
case ND_EQ:
return eval(node->lhs) == eval(node->rhs);
case ND_NE:
return eval(node->lhs) != eval(node->rhs);
case ND_LT:
if (node->lhs->ty->is_unsigned)
return (uint64_t)eval(node->lhs) < eval(node->rhs);
return eval(node->lhs) < eval(node->rhs);
case ND_LE:
if (node->lhs->ty->is_unsigned)
return (uint64_t)eval(node->lhs) <= eval(node->rhs);
return eval(node->lhs) <= eval(node->rhs);
case ND_COND:
return eval(node->cond) ? eval2(node->then, label) : eval2(node->els, label);
case ND_COMMA:
return eval2(node->rhs, label);
case ND_NOT:
return !eval(node->lhs);
case ND_BITNOT:
return ~eval(node->lhs);
case ND_LOGAND:
return eval(node->lhs) && eval(node->rhs);
case ND_LOGOR:
return eval(node->lhs) || eval(node->rhs);
case ND_CAST: {
int64_t val = eval2(node->lhs, label);
if (is_integer(node->ty)) {
switch (node->ty->size) {
case 1: return node->ty->is_unsigned ? (uint8_t)val : (int8_t)val;
case 2: return node->ty->is_unsigned ? (uint16_t)val : (int16_t)val;
case 4: return node->ty->is_unsigned ? (uint32_t)val : (int32_t)val;
}
}
return val;
}
case ND_ADDR:
return eval_rval(node->lhs, label);
case ND_MEMBER:
if (!label)
error_tok(node->tok, "not a compile-time constant");
if (node->ty->kind != TY_ARRAY)
error_tok(node->tok, "invalid initializer");
return eval_rval(node->lhs, label) + node->member->offset;
case ND_VAR:
if (!label)
error_tok(node->tok, "not a compile-time constant");
if (node->var->ty->kind != TY_ARRAY && node->var->ty->kind != TY_FUNC)
error_tok(node->tok, "invalid initializer");
*label = node->var->name;
return 0;
case ND_NUM:
return node->val;
}
error_tok(node->tok, "not a compile-time constant");
}
static int64_t eval_rval(Node *node, char **label) {
switch (node->kind) {
case ND_VAR:
if (node->var->is_local)
error_tok(node->tok, "not a compile-time constant");
*label = node->var->name;
return 0;
case ND_DEREF:
return eval2(node->lhs, label);
case ND_MEMBER:
return eval_rval(node->lhs, label) + node->member->offset;
}
error_tok(node->tok, "invalid initializer");
}
static bool is_const_expr(Node *node) {
add_type(node);
switch (node->kind) {
case ND_ADD:
case ND_SUB:
case ND_MUL:
case ND_DIV:
case ND_BITAND:
case ND_BITOR:
case ND_BITXOR:
case ND_SHL:
case ND_SHR:
case ND_EQ:
case ND_NE:
case ND_LT:
case ND_LE:
case ND_LOGAND:
case ND_LOGOR:
return is_const_expr(node->lhs) && is_const_expr(node->rhs);
case ND_COND:
if (!is_const_expr(node->cond))
return false;
return is_const_expr(eval(node->cond) ? node->then : node->els);
case ND_COMMA:
return is_const_expr(node->rhs);
case ND_NEG:
case ND_NOT:
case ND_BITNOT:
case ND_CAST:
return is_const_expr(node->lhs);
case ND_NUM:
return true;
}
return false;
}
int64_t const_expr(Token **rest, Token *tok) {
Node *node = conditional(rest, tok);
return eval(node);
}
static double eval_double(Node *node) {
add_type(node);
if (is_integer(node->ty)) {
if (node->ty->is_unsigned)
return (unsigned long)eval(node);
return eval(node);
}
switch (node->kind) {
case ND_ADD:
return eval_double(node->lhs) + eval_double(node->rhs);
case ND_SUB:
return eval_double(node->lhs) - eval_double(node->rhs);
case ND_MUL:
return eval_double(node->lhs) * eval_double(node->rhs);
case ND_DIV:
return eval_double(node->lhs) / eval_double(node->rhs);
case ND_NEG:
return -eval_double(node->lhs);
case ND_COND:
return eval_double(node->cond) ? eval_double(node->then) : eval_double(node->els);
case ND_COMMA:
return eval_double(node->rhs);
case ND_CAST:
if (is_flonum(node->lhs->ty))
return eval_double(node->lhs);
return eval(node->lhs);
case ND_NUM:
return node->fval;
}
error_tok(node->tok, "not a compile-time constant");
}
// Convert op= operators to expressions containing an assignment.
//
// In general, `A op= C` is converted to ``tmp = &A, *tmp = *tmp op B`.
// However, if a given expression is of form `A.x op= C`, the input is
// converted to `tmp = &A, (*tmp).x = (*tmp).x op C` to handle assignments
// to bitfields.
static Node *to_assign(Node *binary) {
add_type(binary->lhs);
add_type(binary->rhs);
Token *tok = binary->tok;
// Convert `A.x op= C` to `tmp = &A, (*tmp).x = (*tmp).x op C`.
if (binary->lhs->kind == ND_MEMBER) {
Obj *var = new_lvar("", pointer_to(binary->lhs->lhs->ty));
Node *expr1 = new_binary(ND_ASSIGN, new_var_node(var, tok),
new_unary(ND_ADDR, binary->lhs->lhs, tok), tok);
Node *expr2 = new_unary(ND_MEMBER,
new_unary(ND_DEREF, new_var_node(var, tok), tok),
tok);
expr2->member = binary->lhs->member;
Node *expr3 = new_unary(ND_MEMBER,
new_unary(ND_DEREF, new_var_node(var, tok), tok),
tok);
expr3->member = binary->lhs->member;
Node *expr4 = new_binary(ND_ASSIGN, expr2,
new_binary(binary->kind, expr3, binary->rhs, tok),
tok);
return new_binary(ND_COMMA, expr1, expr4, tok);
}
// Convert `A op= C` to ``tmp = &A, *tmp = *tmp op B`.
Obj *var = new_lvar("", pointer_to(binary->lhs->ty));
Node *expr1 = new_binary(ND_ASSIGN, new_var_node(var, tok),
new_unary(ND_ADDR, binary->lhs, tok), tok);
Node *expr2 =
new_binary(ND_ASSIGN,
new_unary(ND_DEREF, new_var_node(var, tok), tok),
new_binary(binary->kind,
new_unary(ND_DEREF, new_var_node(var, tok), tok),
binary->rhs,
tok),
tok);
return new_binary(ND_COMMA, expr1, expr2, tok);
}
// assign = conditional (assign-op assign)?
// assign-op = "=" | "+=" | "-=" | "*=" | "/=" | "%=" | "&=" | "|=" | "^="
// | "<<=" | ">>="
static Node *assign(Token **rest, Token *tok) {
Node *node = conditional(&tok, tok);
if (equal(tok, "="))
return new_binary(ND_ASSIGN, node, assign(rest, tok->next), tok);
if (equal(tok, "+="))
return to_assign(new_add(node, assign(rest, tok->next), tok));
if (equal(tok, "-="))
return to_assign(new_sub(node, assign(rest, tok->next), tok));
if (equal(tok, "*="))
return to_assign(new_binary(ND_MUL, node, assign(rest, tok->next), tok));
if (equal(tok, "/="))
return to_assign(new_binary(ND_DIV, node, assign(rest, tok->next), tok));
if (equal(tok, "%="))
return to_assign(new_binary(ND_MOD, node, assign(rest, tok->next), tok));
if (equal(tok, "&="))
return to_assign(new_binary(ND_BITAND, node, assign(rest, tok->next), tok));
if (equal(tok, "|="))
return to_assign(new_binary(ND_BITOR, node, assign(rest, tok->next), tok));
if (equal(tok, "^="))
return to_assign(new_binary(ND_BITXOR, node, assign(rest, tok->next), tok));
if (equal(tok, "<<="))
return to_assign(new_binary(ND_SHL, node, assign(rest, tok->next), tok));
if (equal(tok, ">>="))
return to_assign(new_binary(ND_SHR, node, assign(rest, tok->next), tok));
*rest = tok;
return node;
}
// conditional = logor ("?" expr? ":" conditional)?
static Node *conditional(Token **rest, Token *tok) {
Node *cond = logor(&tok, tok);
if (!equal(tok, "?")) {
*rest = tok;
return cond;
}
if (equal(tok->next, ":")) {
// [GNU] Compile `a ?: b` as `tmp = a, tmp ? tmp : b`.
add_type(cond);
Obj *var = new_lvar("", cond->ty);
Node *lhs = new_binary(ND_ASSIGN, new_var_node(var, tok), cond, tok);
Node *rhs = new_node(ND_COND, tok);
rhs->cond = new_var_node(var, tok);
rhs->then = new_var_node(var, tok);
rhs->els = conditional(rest, tok->next->next);
return new_binary(ND_COMMA, lhs, rhs, tok);
}
Node *node = new_node(ND_COND, tok);
node->cond = cond;
node->then = expr(&tok, tok->next);
tok = skip(tok, ":");
node->els = conditional(rest, tok);
return node;
}
// logor = logand ("||" logand)*
static Node *logor(Token **rest, Token *tok) {
Node *node = logand(&tok, tok);
while (equal(tok, "||")) {
Token *start = tok;
node = new_binary(ND_LOGOR, node, logand(&tok, tok->next), start);
}
*rest = tok;
return node;
}
// logand = bitor ("&&" bitor)*
static Node *logand(Token **rest, Token *tok) {
Node *node = bitor(&tok, tok);
while (equal(tok, "&&")) {
Token *start = tok;
node = new_binary(ND_LOGAND, node, bitor(&tok, tok->next), start);
}
*rest = tok;
return node;
}
// bitor = bitxor ("|" bitxor)*
static Node *bitor(Token **rest, Token *tok) {
Node *node = bitxor(&tok, tok);
while (equal(tok, "|")) {
Token *start = tok;
node = new_binary(ND_BITOR, node, bitxor(&tok, tok->next), start);
}
*rest = tok;
return node;
}
// bitxor = bitand ("^" bitand)*
static Node *bitxor(Token **rest, Token *tok) {
Node *node = bitand(&tok, tok);
while (equal(tok, "^")) {
Token *start = tok;
node = new_binary(ND_BITXOR, node, bitand(&tok, tok->next), start);
}
*rest = tok;
return node;
}
// bitand = equality ("&" equality)*
static Node *bitand(Token **rest, Token *tok) {
Node *node = equality(&tok, tok);
while (equal(tok, "&")) {
Token *start = tok;
node = new_binary(ND_BITAND, node, equality(&tok, tok->next), start);
}
*rest = tok;
return node;
}
// equality = relational ("==" relational | "!=" relational)*
static Node *equality(Token **rest, Token *tok) {
Node *node = relational(&tok, tok);
for (;;) {
Token *start = tok;
if (equal(tok, "==")) {
node = new_binary(ND_EQ, node, relational(&tok, tok->next), start);
continue;
}
if (equal(tok, "!=")) {
node = new_binary(ND_NE, node, relational(&tok, tok->next), start);
continue;
}
*rest = tok;
return node;
}
}
// relational = shift ("<" shift | "<=" shift | ">" shift | ">=" shift)*
static Node *relational(Token **rest, Token *tok) {
Node *node = shift(&tok, tok);
for (;;) {
Token *start = tok;
if (equal(tok, "<")) {
node = new_binary(ND_LT, node, shift(&tok, tok->next), start);
continue;
}
if (equal(tok, "<=")) {
node = new_binary(ND_LE, node, shift(&tok, tok->next), start);
continue;
}
if (equal(tok, ">")) {
node = new_binary(ND_LT, shift(&tok, tok->next), node, start);
continue;
}
if (equal(tok, ">=")) {
node = new_binary(ND_LE, shift(&tok, tok->next), node, start);
continue;
}
*rest = tok;
return node;
}
}
// shift = add ("<<" add | ">>" add)*
static Node *shift(Token **rest, Token *tok) {
Node *node = add(&tok, tok);
for (;;) {
Token *start = tok;
if (equal(tok, "<<")) {
node = new_binary(ND_SHL, node, add(&tok, tok->next), start);
continue;
}
if (equal(tok, ">>")) {
node = new_binary(ND_SHR, node, add(&tok, tok->next), start);
continue;
}
*rest = tok;
return node;
}
}
// In C, `+` operator is overloaded to perform the pointer arithmetic.
// If p is a pointer, p+n adds not n but sizeof(*p)*n to the value of p,
// so that p+n points to the location n elements (not bytes) ahead of p.
// In other words, we need to scale an integer value before adding to a
// pointer value. This function takes care of the scaling.
static Node *new_add(Node *lhs, Node *rhs, Token *tok) {
add_type(lhs);
add_type(rhs);
// num + num
if (is_numeric(lhs->ty) && is_numeric(rhs->ty))
return new_binary(ND_ADD, lhs, rhs, tok);
if (lhs->ty->base && rhs->ty->base)
error_tok(tok, "invalid operands");
// Canonicalize `num + ptr` to `ptr + num`.
if (!lhs->ty->base && rhs->ty->base) {
Node *tmp = lhs;
lhs = rhs;
rhs = tmp;
}
// VLA + num
if (lhs->ty->base->kind == TY_VLA) {
rhs = new_binary(ND_MUL, rhs, new_var_node(lhs->ty->base->vla_size, tok), tok);
return new_binary(ND_ADD, lhs, rhs, tok);
}
// ptr + num
rhs = new_binary(ND_MUL, rhs, new_long(lhs->ty->base->size, tok), tok);
return new_binary(ND_ADD, lhs, rhs, tok);
}
// Like `+`, `-` is overloaded for the pointer type.
static Node *new_sub(Node *lhs, Node *rhs, Token *tok) {
add_type(lhs);
add_type(rhs);
// num - num
if (is_numeric(lhs->ty) && is_numeric(rhs->ty))
return new_binary(ND_SUB, lhs, rhs, tok);
// VLA + num
if (lhs->ty->base->kind == TY_VLA) {
rhs = new_binary(ND_MUL, rhs, new_var_node(lhs->ty->base->vla_size, tok), tok);
add_type(rhs);
Node *node = new_binary(ND_SUB, lhs, rhs, tok);
node->ty = lhs->ty;
return node;
}
// ptr - num
if (lhs->ty->base && is_integer(rhs->ty)) {
rhs = new_binary(ND_MUL, rhs, new_long(lhs->ty->base->size, tok), tok);
add_type(rhs);
Node *node = new_binary(ND_SUB, lhs, rhs, tok);
node->ty = lhs->ty;
return node;
}
// ptr - ptr, which returns how many elements are between the two.
if (lhs->ty->base && rhs->ty->base) {
Node *node = new_binary(ND_SUB, lhs, rhs, tok);
node->ty = ty_long;
return new_binary(ND_DIV, node, new_num(lhs->ty->base->size, tok), tok);
}
error_tok(tok, "invalid operands");
}
// add = mul ("+" mul | "-" mul)*
static Node *add(Token **rest, Token *tok) {
Node *node = mul(&tok, tok);
for (;;) {
Token *start = tok;
if (equal(tok, "+")) {
node = new_add(node, mul(&tok, tok->next), start);
continue;
}
if (equal(tok, "-")) {
node = new_sub(node, mul(&tok, tok->next), start);
continue;
}
*rest = tok;
return node;
}
}
// mul = cast ("*" cast | "/" cast | "%" cast)*
static Node *mul(Token **rest, Token *tok) {
Node *node = cast(&tok, tok);
for (;;) {
Token *start = tok;
if (equal(tok, "*")) {
node = new_binary(ND_MUL, node, cast(&tok, tok->next), start);
continue;
}
if (equal(tok, "/")) {
node = new_binary(ND_DIV, node, cast(&tok, tok->next), start);
continue;
}
if (equal(tok, "%")) {
node = new_binary(ND_MOD, node, cast(&tok, tok->next), start);
continue;
}
*rest = tok;
return node;
}
}
// cast = "(" type-name ")" cast | unary
static Node *cast(Token **rest, Token *tok) {
if (equal(tok, "(") && is_typename(tok->next)) {
Token *start = tok;
Type *ty = typename(&tok, tok->next);
tok = skip(tok, ")");
// compound literal
if (equal(tok, "{"))
return unary(rest, start);
// type cast
Node *node = new_cast(cast(rest, tok), ty);
node->tok = start;
return node;
}
return unary(rest, tok);
}
// unary = ("+" | "-" | "*" | "&" | "!" | "~") cast
// | ("++" | "--") unary
// | "&&" ident
// | postfix
static Node *unary(Token **rest, Token *tok) {
if (equal(tok, "+"))
return cast(rest, tok->next);
if (equal(tok, "-"))
return new_unary(ND_NEG, cast(rest, tok->next), tok);
if (equal(tok, "&")) {
Node *lhs = cast(rest, tok->next);
add_type(lhs);
if (lhs->kind == ND_MEMBER && lhs->member->is_bitfield)
error_tok(tok, "cannot take address of bitfield");
return new_unary(ND_ADDR, lhs, tok);
}
if (equal(tok, "*")) {
// [https://www.sigbus.info/n1570#6.5.3.2p4] This is an oddity
// in the C spec, but dereferencing a function shouldn't do
// anything. If foo is a function, `*foo`, `**foo` or `*****foo`
// are all equivalent to just `foo`.
Node *node = cast(rest, tok->next);
add_type(node);
if (node->ty->kind == TY_FUNC)
return node;
return new_unary(ND_DEREF, node, tok);
}
if (equal(tok, "!"))
return new_unary(ND_NOT, cast(rest, tok->next), tok);
if (equal(tok, "~"))
return new_unary(ND_BITNOT, cast(rest, tok->next), tok);
// Read ++i as i+=1
if (equal(tok, "++"))
return to_assign(new_add(unary(rest, tok->next), new_num(1, tok), tok));
// Read --i as i-=1
if (equal(tok, "--"))
return to_assign(new_sub(unary(rest, tok->next), new_num(1, tok), tok));
// [GNU] labels-as-values
if (equal(tok, "&&")) {
Node *node = new_node(ND_LABEL_VAL, tok);
node->label = get_ident(tok->next);
node->goto_next = gotos;
gotos = node;
*rest = tok->next->next;
return node;
}
return postfix(rest, tok);
}
// struct-members = (declspec declarator ("," declarator)* ";")*
static void struct_members(Token **rest, Token *tok, Type *ty) {
Member head = {};
Member *cur = &head;
int idx = 0;
while (!equal(tok, "}")) {
VarAttr attr = {};
Type *basety = declspec(&tok, tok, &attr);
bool first = true;
// Anonymous struct member
if ((basety->kind == TY_STRUCT || basety->kind == TY_UNION) &&
consume(&tok, tok, ";")) {
Member *mem = calloc(1, sizeof(Member));
mem->ty = basety;
mem->idx = idx++;
mem->align = attr.align ? attr.align : mem->ty->align;
cur = cur->next = mem;
continue;
}
// Regular struct members
while (!consume(&tok, tok, ";")) {
if (!first)
tok = skip(tok, ",");
first = false;
Member *mem = calloc(1, sizeof(Member));
mem->ty = declarator(&tok, tok, basety);
mem->name = mem->ty->name;
mem->idx = idx++;
mem->align = attr.align ? attr.align : mem->ty->align;
if (consume(&tok, tok, ":")) {
mem->is_bitfield = true;
mem->bit_width = const_expr(&tok, tok);
}
cur = cur->next = mem;
}
}
// If the last element is an array of incomplete type, it's
// called a "flexible array member". It should behave as if
// if were a zero-sized array.
if (cur != &head && cur->ty->kind == TY_ARRAY && cur->ty->array_len < 0) {
cur->ty = array_of(cur->ty->base, 0);
ty->is_flexible = true;
}
*rest = tok->next;
ty->members = head.next;
}
// struct-union-decl = ident? ("{" struct-members)?
static Type *struct_union_decl(Token **rest, Token *tok) {
// Read a tag.
Token *tag = NULL;
if (tok->kind == TK_IDENT) {
tag = tok;
tok = tok->next;
}
if (tag && !equal(tok, "{")) {
*rest = tok;
Type *ty = find_tag(tag);
if (ty)
return ty;
ty = struct_type();
ty->size = -1;
push_tag_scope(tag, ty);
return ty;
}
tok = skip(tok, "{");
// Construct a struct object.
Type *ty = struct_type();
struct_members(rest, tok, ty);
if (tag) {
// If this is a redefinition, overwrite a previous type.
// Otherwise, register the struct type.
for (TagScope *sc = scope->tags; sc; sc = sc->next) {
if (equal(tag, sc->name)) {
*sc->ty = *ty;
return sc->ty;
}
}
push_tag_scope(tag, ty);
}
return ty;
}
// struct-decl = struct-union-decl
static Type *struct_decl(Token **rest, Token *tok) {
Type *ty = struct_union_decl(rest, tok);
ty->kind = TY_STRUCT;
if (ty->size < 0)
return ty;
// Assign offsets within the struct to members.
int bits = 0;
for (Member *mem = ty->members; mem; mem = mem->next) {
if (mem->is_bitfield && mem->bit_width == 0) {
// Zero-width anonymous bitfield has a special meaning.
// It affects only alignment.
bits = align_to(bits, mem->ty->size * 8);
} else if (mem->is_bitfield) {
int sz = mem->ty->size;
if (bits / (sz * 8) != (bits + mem->bit_width - 1) / (sz * 8))
bits = align_to(bits, sz * 8);
mem->offset = align_down(bits / 8, sz);
mem->bit_offset = bits % (sz * 8);
bits += mem->bit_width;
} else {
bits = align_to(bits, mem->align * 8);
mem->offset = bits / 8;
bits += mem->ty->size * 8;
}
if (ty->align < mem->align)
ty->align = mem->align;
}
ty->size = align_to(bits, ty->align * 8) / 8;
return ty;
}
// union-decl = struct-union-decl
static Type *union_decl(Token **rest, Token *tok) {
Type *ty = struct_union_decl(rest, tok);
ty->kind = TY_UNION;
if (ty->size < 0)
return ty;
// If union, we don't have to assign offsets because they
// are already initialized to zero. We need to compute the
// alignment and the size though.
for (Member *mem = ty->members; mem; mem = mem->next) {
if (ty->align < mem->align)
ty->align = mem->align;
if (ty->size < mem->ty->size)
ty->size = mem->ty->size;
}
ty->size = align_to(ty->size, ty->align);
return ty;
}
// Find a struct member by name.
static Member *get_struct_member(Type *ty, Token *tok) {
for (Member *mem = ty->members; mem; mem = mem->next) {
// Anonymous struct member
if ((mem->ty->kind == TY_STRUCT || mem->ty->kind == TY_UNION) &&
!mem->name) {
if (get_struct_member(mem->ty, tok))
return mem;
continue;
}
// Regular struct member
if (mem->name->len == tok->len &&
!strncmp(mem->name->loc, tok->loc, tok->len))
return mem;
}
return NULL;
}
// Create a node representing a struct member access, such as foo.bar
// where foo is a struct and bar is a member name.
//
// C has a feature called "anonymous struct" which allows a struct to
// have another unnamed struct as a member like this:
//
// struct { struct { int a; }; int b; } x;
//
// The members of an anonymous struct belong to the outer struct's
// member namespace. Therefore, in the above example, you can access
// member "a" of the anonymous struct as "x.a".
//
// This function takes care of anonymous structs.
static Node *struct_ref(Node *node, Token *tok) {
add_type(node);
if (node->ty->kind != TY_STRUCT && node->ty->kind != TY_UNION)
error_tok(node->tok, "not a struct nor a union");
Type *ty = node->ty;
for (;;) {
Member *mem = get_struct_member(ty, tok);
if (!mem)
error_tok(tok, "no such member");
node = new_unary(ND_MEMBER, node, tok);
node->member = mem;
if (mem->name)
break;
ty = mem->ty;
}
return node;
}
// Convert A++ to `(typeof A)((A += 1) - 1)`
static Node *new_inc_dec(Node *node, Token *tok, int addend) {
add_type(node);
return new_cast(new_add(to_assign(new_add(node, new_num(addend, tok), tok)),
new_num(-addend, tok), tok),
node->ty);
}
// postfix = "(" type-name ")" "{" initializer-list "}"
// = ident "(" func-args ")" postfix-tail*
// | primary postfix-tail*
//
// postfix-tail = "[" expr "]"
// | "(" func-args ")"
// | "." ident
// | "->" ident
// | "++"
// | "--"
static Node *postfix(Token **rest, Token *tok) {
if (equal(tok, "(") && is_typename(tok->next)) {
// Compound literal
Token *start = tok;
Type *ty = typename(&tok, tok->next);
tok = skip(tok, ")");
if (scope->next == NULL) {
Obj *var = new_anon_gvar(ty);
gvar_initializer(rest, tok, var);
return new_var_node(var, start);
}
Obj *var = new_lvar("", ty);
Node *lhs = lvar_initializer(rest, tok, var);
Node *rhs = new_var_node(var, tok);
return new_binary(ND_COMMA, lhs, rhs, start);
}
Node *node = primary(&tok, tok);
for (;;) {
if (equal(tok, "(")) {
node = funcall(&tok, tok->next, node);
continue;
}
if (equal(tok, "[")) {
// x[y] is short for *(x+y)
Token *start = tok;
Node *idx = expr(&tok, tok->next);
tok = skip(tok, "]");
node = new_unary(ND_DEREF, new_add(node, idx, start), start);
continue;
}
if (equal(tok, ".")) {
node = struct_ref(node, tok->next);
tok = tok->next->next;
continue;
}
if (equal(tok, "->")) {
// x->y is short for (*x).y
node = new_unary(ND_DEREF, node, tok);
node = struct_ref(node, tok->next);
tok = tok->next->next;
continue;
}
if (equal(tok, "++")) {
node = new_inc_dec(node, tok, 1);
tok = tok->next;
continue;
}
if (equal(tok, "--")) {
node = new_inc_dec(node, tok, -1);
tok = tok->next;
continue;
}
*rest = tok;
return node;
}
}
// funcall = (assign ("," assign)*)? ")"
static Node *funcall(Token **rest, Token *tok, Node *fn) {
add_type(fn);
if (fn->ty->kind != TY_FUNC &&
(fn->ty->kind != TY_PTR || fn->ty->base->kind != TY_FUNC))
error_tok(fn->tok, "not a function");
Type *ty = (fn->ty->kind == TY_FUNC) ? fn->ty : fn->ty->base;
Type *param_ty = ty->params;
Node head = {};
Node *cur = &head;
while (!equal(tok, ")")) {
if (cur != &head)
tok = skip(tok, ",");
Node *arg = assign(&tok, tok);
add_type(arg);
if (!param_ty && !ty->is_variadic)
error_tok(tok, "too many arguments");
if (param_ty) {
if (param_ty->kind != TY_STRUCT && param_ty->kind != TY_UNION)
arg = new_cast(arg, param_ty);
param_ty = param_ty->next;
} else if (arg->ty->kind == TY_FLOAT) {
// If parameter type is omitted (e.g. in "..."), float
// arguments are promoted to double.
arg = new_cast(arg, ty_double);
}
cur = cur->next = arg;
}
if (param_ty)
error_tok(tok, "too few arguments");
*rest = skip(tok, ")");
Node *node = new_unary(ND_FUNCALL, fn, tok);
node->func_ty = ty;
node->ty = ty->return_ty;
node->args = head.next;
// If a function returns a struct, it is caller's responsibility
// to allocate a space for the return value.
if (node->ty->kind == TY_STRUCT || node->ty->kind == TY_UNION)
node->ret_buffer = new_lvar("", node->ty);
return node;
}
// generic-selection = "(" assign "," generic-assoc ("," generic-assoc)* ")"
//
// generic-assoc = type-name ":" assign
// | "default" ":" assign
static Node *generic_selection(Token **rest, Token *tok) {
Token *start = tok;
tok = skip(tok, "(");
Node *ctrl = assign(&tok, tok);
add_type(ctrl);
Type *t1 = ctrl->ty;
if (t1->kind == TY_FUNC)
t1 = pointer_to(t1);
else if (t1->kind == TY_ARRAY)
t1 = pointer_to(t1->base);
Node *ret = NULL;
while (!consume(rest, tok, ")")) {
tok = skip(tok, ",");
if (equal(tok, "default")) {
tok = skip(tok->next, ":");
Node *node = assign(&tok, tok);
if (!ret)
ret = node;
continue;
}
Type *t2 = typename(&tok, tok);
tok = skip(tok, ":");
Node *node = assign(&tok, tok);
if (is_compatible(t1, t2))
ret = node;
}
if (!ret)
error_tok(start, "controlling expression type not compatible with"
" any generic association type");
return ret;
}
// primary = "(" "{" stmt+ "}" ")"
// | "(" expr ")"
// | "sizeof" "(" type-name ")"
// | "sizeof" unary
// | "_Alignof" "(" type-name ")"
// | "_Alignof" unary
// | "_Generic" generic-selection
// | "__builtin_types_compatible_p" "(" type-name, type-name, ")"
// | "__builtin_reg_class" "(" type-name ")"
// | ident
// | str
// | num
static Node *primary(Token **rest, Token *tok) {
Token *start = tok;
if (equal(tok, "(") && equal(tok->next, "{")) {
// This is a GNU statement expresssion.
Node *node = new_node(ND_STMT_EXPR, tok);
node->body = compound_stmt(&tok, tok->next->next)->body;
*rest = skip(tok, ")");
return node;
}
if (equal(tok, "(")) {
Node *node = expr(&tok, tok->next);
*rest = skip(tok, ")");
return node;
}
if (equal(tok, "sizeof") && equal(tok->next, "(") && is_typename(tok->next->next)) {
Type *ty = typename(&tok, tok->next->next);
*rest = skip(tok, ")");
if (ty->kind == TY_VLA) {
if (ty->vla_size)
return new_var_node(ty->vla_size, tok);
Node *lhs = compute_vla_size(ty, tok);
Node *rhs = new_var_node(ty->vla_size, tok);
return new_binary(ND_COMMA, lhs, rhs, tok);
}
return new_ulong(ty->size, start);
}
if (equal(tok, "sizeof")) {
Node *node = unary(rest, tok->next);
add_type(node);
if (node->ty->kind == TY_VLA)
return new_var_node(node->ty->vla_size, tok);
return new_ulong(node->ty->size, tok);
}
if (equal(tok, "_Alignof") && equal(tok->next, "(") && is_typename(tok->next->next)) {
Type *ty = typename(&tok, tok->next->next);
*rest = skip(tok, ")");
return new_ulong(ty->align, tok);
}
if (equal(tok, "_Alignof")) {
Node *node = unary(rest, tok->next);
add_type(node);
return new_ulong(node->ty->align, tok);
}
if (equal(tok, "_Generic"))
return generic_selection(rest, tok->next);
if (equal(tok, "__builtin_types_compatible_p")) {
tok = skip(tok->next, "(");
Type *t1 = typename(&tok, tok);
tok = skip(tok, ",");
Type *t2 = typename(&tok, tok);
*rest = skip(tok, ")");
return new_num(is_compatible(t1, t2), start);
}
if (equal(tok, "__builtin_reg_class")) {
tok = skip(tok->next, "(");
Type *ty = typename(&tok, tok);
*rest = skip(tok, ")");
if (is_integer(ty) || ty->kind == TY_PTR)
return new_num(0, start);
if (is_flonum(ty))
return new_num(1, start);
return new_num(2, start);
}
if (tok->kind == TK_IDENT) {
// Variable or enum constant
VarScope *sc = find_var(tok);
*rest = tok->next;
// For "static inline" function
if (sc && sc->var && sc->var->is_function) {
if (current_fn)
strarray_push(&current_fn->refs, sc->var->name);
else
sc->var->is_root = true;
}
if (sc) {
if (sc->var)
return new_var_node(sc->var, tok);
if (sc->enum_ty)
return new_num(sc->enum_val, tok);
}
if (equal(tok->next, "("))
error_tok(tok, "implicit declaration of a function");
error_tok(tok, "undefined variable");
}
if (tok->kind == TK_STR) {
Obj *var = new_string_literal(tok->str, tok->ty);
*rest = tok->next;
return new_var_node(var, tok);
}
if (tok->kind == TK_NUM) {
Node *node;
if (is_flonum(tok->ty)) {
node = new_node(ND_NUM, tok);
node->fval = tok->fval;
} else {
node = new_num(tok->val, tok);
}
node->ty = tok->ty;
*rest = tok->next;
return node;
}
error_tok(tok, "expected an expression");
}
static Token *parse_typedef(Token *tok, Type *basety) {
bool first = true;
while (!consume(&tok, tok, ";")) {
if (!first)
tok = skip(tok, ",");
first = false;
Type *ty = declarator(&tok, tok, basety);
if (!ty->name)
error_tok(ty->name_pos, "typedef name omitted");
push_scope(get_ident(ty->name))->type_def = ty;
}
return tok;
}
static void create_param_lvars(Type *param) {
if (param) {
create_param_lvars(param->next);
if (!param->name)
error_tok(param->name_pos, "parameter name omitted");
new_lvar(get_ident(param->name), param);
}
}
// This function matches gotos or labels-as-values with labels.
//
// We cannot resolve gotos as we parse a function because gotos
// can refer a label that appears later in the function.
// So, we need to do this after we parse the entire function.
static void resolve_goto_labels(void) {
for (Node *x = gotos; x; x = x->goto_next) {
for (Node *y = labels; y; y = y->goto_next) {
if (!strcmp(x->label, y->label)) {
x->unique_label = y->unique_label;
break;
}
}
if (x->unique_label == NULL)
error_tok(x->tok->next, "use of undeclared label");
}
gotos = labels = NULL;
}
static Obj *find_func(char *name) {
Scope *sc = scope;
while (sc->next)
sc = sc->next;
for (VarScope *sc2 = sc->vars; sc2; sc2 = sc2->next)
if (!strcmp(sc2->name, name) && sc2->var && sc2->var->is_function)
return sc2->var;
return NULL;
}
static void mark_live(Obj *var) {
if (!var->is_function || var->is_live)
return;
var->is_live = true;
for (int i = 0; i < var->refs.len; i++) {
Obj *fn = find_func(var->refs.data[i]);
if (fn)
mark_live(fn);
}
}
static Token *function(Token *tok, Type *basety, VarAttr *attr) {
Type *ty = declarator(&tok, tok, basety);
if (!ty->name)
error_tok(ty->name_pos, "function name omitted");
Obj *fn = new_gvar(get_ident(ty->name), ty);
fn->is_function = true;
fn->is_definition = !consume(&tok, tok, ";");
fn->is_static = attr->is_static || (attr->is_inline && !attr->is_extern);
fn->is_inline = attr->is_inline;
fn->is_root = !(fn->is_static && fn->is_inline);
if (!fn->is_definition)
return tok;
current_fn = fn;
locals = NULL;
enter_scope();
create_param_lvars(ty->params);
// A buffer for a struct/union return value is passed
// as the hidden first parameter.
Type *rty = ty->return_ty;
if ((rty->kind == TY_STRUCT || rty->kind == TY_UNION) && rty->size > 16)
new_lvar("", pointer_to(rty));
fn->params = locals;
if (ty->is_variadic)
fn->va_area = new_lvar("__va_area__", array_of(ty_char, 136));
fn->alloca_bottom = new_lvar("__alloca_size__", pointer_to(ty_char));
tok = skip(tok, "{");
// [https://www.sigbus.info/n1570#6.4.2.2p1] "__func__" is
// automatically defined as a local variable containing the
// current function name.
push_scope("__func__")->var =
new_string_literal(fn->name, array_of(ty_char, strlen(fn->name) + 1));
// [GNU] __FUNCTION__ is yet another name of __func__.
push_scope("__FUNCTION__")->var =
new_string_literal(fn->name, array_of(ty_char, strlen(fn->name) + 1));
fn->body = compound_stmt(&tok, tok);
fn->locals = locals;
leave_scope();
resolve_goto_labels();
return tok;
}
static Token *global_variable(Token *tok, Type *basety, VarAttr *attr) {
bool first = true;
while (!consume(&tok, tok, ";")) {
if (!first)
tok = skip(tok, ",");
first = false;
Type *ty = declarator(&tok, tok, basety);
if (!ty->name)
error_tok(ty->name_pos, "variable name omitted");
Obj *var = new_gvar(get_ident(ty->name), ty);
var->is_definition = !attr->is_extern;
var->is_static = attr->is_static;
var->is_tls = attr->is_tls;
if (attr->align)
var->align = attr->align;
if (equal(tok, "="))
gvar_initializer(&tok, tok->next, var);
else if (!attr->is_extern && !attr->is_tls)
var->is_tentative = true;
}
return tok;
}
// Lookahead tokens and returns true if a given token is a start
// of a function definition or declaration.
static bool is_function(Token *tok) {
if (equal(tok, ";"))
return false;
Type dummy = {};
Type *ty = declarator(&tok, tok, &dummy);
return ty->kind == TY_FUNC;
}
// Remove redundant tentative definitions.
static void scan_globals(void) {
Obj head;
Obj *cur = &head;
for (Obj *var = globals; var; var = var->next) {
if (!var->is_tentative) {
cur = cur->next = var;
continue;
}
// Find another definition of the same identifier.
Obj *var2 = globals;
for (; var2; var2 = var2->next)
if (var != var2 && var2->is_definition && !strcmp(var->name, var2->name))
break;
// If there's another definition, the tentative definition
// is redundant
if (!var2)
cur = cur->next = var;
}
cur->next = NULL;
globals = head.next;
}
static void declare_builtin_functions(void) {
Type *ty = func_type(pointer_to(ty_void));
ty->params = copy_type(ty_int);
builtin_alloca = new_gvar("alloca", ty);
builtin_alloca->is_definition = false;
}
// program = (typedef | function-definition | global-variable)*
Obj *parse(Token *tok) {
declare_builtin_functions();
globals = NULL;
while (tok->kind != TK_EOF) {
VarAttr attr = {};
Type *basety = declspec(&tok, tok, &attr);
// Typedef
if (attr.is_typedef) {
tok = parse_typedef(tok, basety);
continue;
}
// Function
if (is_function(tok)) {
tok = function(tok, basety, &attr);
continue;
}
// Global variable
tok = global_variable(tok, basety, &attr);
}
for (Obj *var = globals; var; var = var->next)
if (var->is_root)
mark_live(var);
// Remove redundant tentative definitions.
scan_globals();
return globals;
}
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