From 0f232d8eaee1f94896596a9969982297cee7dc67 Mon Sep 17 00:00:00 2001
From: Michael Smith <mikesmiffy128@gmail.com>
Date: Wed, 29 Dec 2021 18:33:40 +0000
Subject: Remove some unused files

---
 src/3p/chibicc/preprocess.c | 1208 -------------------------------------------
 1 file changed, 1208 deletions(-)
 delete mode 100644 src/3p/chibicc/preprocess.c

(limited to 'src/3p/chibicc/preprocess.c')

diff --git a/src/3p/chibicc/preprocess.c b/src/3p/chibicc/preprocess.c
deleted file mode 100644
index cd8d1d8..0000000
--- a/src/3p/chibicc/preprocess.c
+++ /dev/null
@@ -1,1208 +0,0 @@
-// This file implements the C preprocessor.
-//
-// The preprocessor takes a list of tokens as an input and returns a
-// new list of tokens as an output.
-//
-// The preprocessing language is designed in such a way that that's
-// guaranteed to stop even if there is a recursive macro.
-// Informally speaking, a macro is applied only once for each token.
-// That is, if a macro token T appears in a result of direct or
-// indirect macro expansion of T, T won't be expanded any further.
-// For example, if T is defined as U, and U is defined as T, then
-// token T is expanded to U and then to T and the macro expansion
-// stops at that point.
-//
-// To achieve the above behavior, we attach for each token a set of
-// macro names from which the token is expanded. The set is called
-// "hideset". Hideset is initially empty, and every time we expand a
-// macro, the macro name is added to the resulting tokens' hidesets.
-//
-// The above macro expansion algorithm is explained in this document
-// written by Dave Prossor, which is used as a basis for the
-// standard's wording:
-// https://github.com/rui314/chibicc/wiki/cpp.algo.pdf
-
-#include "chibicc.h"
-
-typedef struct MacroParam MacroParam;
-struct MacroParam {
-  MacroParam *next;
-  char *name;
-};
-
-typedef struct MacroArg MacroArg;
-struct MacroArg {
-  MacroArg *next;
-  char *name;
-  bool is_va_args;
-  Token *tok;
-};
-
-typedef Token *macro_handler_fn(Token *);
-
-typedef struct Macro Macro;
-struct Macro {
-  char *name;
-  bool is_objlike; // Object-like or function-like
-  MacroParam *params;
-  char *va_args_name;
-  Token *body;
-  macro_handler_fn *handler;
-};
-
-// `#if` can be nested, so we use a stack to manage nested `#if`s.
-typedef struct CondIncl CondIncl;
-struct CondIncl {
-  CondIncl *next;
-  enum { IN_THEN, IN_ELIF, IN_ELSE } ctx;
-  Token *tok;
-  bool included;
-};
-
-typedef struct Hideset Hideset;
-struct Hideset {
-  Hideset *next;
-  char *name;
-};
-
-static HashMap macros;
-static CondIncl *cond_incl;
-static HashMap pragma_once;
-static int include_next_idx;
-
-static Token *preprocess2(Token *tok);
-static Macro *find_macro(Token *tok);
-
-static bool is_hash(Token *tok) {
-  return tok->at_bol && equal(tok, "#");
-}
-
-// Some preprocessor directives such as #include allow extraneous
-// tokens before newline. This function skips such tokens.
-static Token *skip_line(Token *tok) {
-  if (tok->at_bol)
-    return tok;
-  warn_tok(tok, "extra token");
-  while (!tok->at_bol)
-    tok = tok->next;
-  return tok;
-}
-
-static Token *copy_token(Token *tok) {
-  Token *t = calloc(1, sizeof(Token));
-  *t = *tok;
-  t->next = NULL;
-  return t;
-}
-
-static Token *new_eof(Token *tok) {
-  Token *t = copy_token(tok);
-  t->kind = TK_EOF;
-  t->len = 0;
-  return t;
-}
-
-static Hideset *new_hideset(char *name) {
-  Hideset *hs = calloc(1, sizeof(Hideset));
-  hs->name = name;
-  return hs;
-}
-
-static Hideset *hideset_union(Hideset *hs1, Hideset *hs2) {
-  Hideset head = {};
-  Hideset *cur = &head;
-
-  for (; hs1; hs1 = hs1->next)
-    cur = cur->next = new_hideset(hs1->name);
-  cur->next = hs2;
-  return head.next;
-}
-
-static bool hideset_contains(Hideset *hs, char *s, int len) {
-  for (; hs; hs = hs->next)
-    if (strlen(hs->name) == len && !strncmp(hs->name, s, len))
-      return true;
-  return false;
-}
-
-static Hideset *hideset_intersection(Hideset *hs1, Hideset *hs2) {
-  Hideset head = {};
-  Hideset *cur = &head;
-
-  for (; hs1; hs1 = hs1->next)
-    if (hideset_contains(hs2, hs1->name, strlen(hs1->name)))
-      cur = cur->next = new_hideset(hs1->name);
-  return head.next;
-}
-
-static Token *add_hideset(Token *tok, Hideset *hs) {
-  Token head = {};
-  Token *cur = &head;
-
-  for (; tok; tok = tok->next) {
-    Token *t = copy_token(tok);
-    t->hideset = hideset_union(t->hideset, hs);
-    cur = cur->next = t;
-  }
-  return head.next;
-}
-
-// Append tok2 to the end of tok1.
-static Token *append(Token *tok1, Token *tok2) {
-  if (tok1->kind == TK_EOF)
-    return tok2;
-
-  Token head = {};
-  Token *cur = &head;
-
-  for (; tok1->kind != TK_EOF; tok1 = tok1->next)
-    cur = cur->next = copy_token(tok1);
-  cur->next = tok2;
-  return head.next;
-}
-
-static Token *skip_cond_incl2(Token *tok) {
-  while (tok->kind != TK_EOF) {
-    if (is_hash(tok) &&
-        (equal(tok->next, "if") || equal(tok->next, "ifdef") ||
-         equal(tok->next, "ifndef"))) {
-      tok = skip_cond_incl2(tok->next->next);
-      continue;
-    }
-    if (is_hash(tok) && equal(tok->next, "endif"))
-      return tok->next->next;
-    tok = tok->next;
-  }
-  return tok;
-}
-
-// Skip until next `#else`, `#elif` or `#endif`.
-// Nested `#if` and `#endif` are skipped.
-static Token *skip_cond_incl(Token *tok) {
-  while (tok->kind != TK_EOF) {
-    if (is_hash(tok) &&
-        (equal(tok->next, "if") || equal(tok->next, "ifdef") ||
-         equal(tok->next, "ifndef"))) {
-      tok = skip_cond_incl2(tok->next->next);
-      continue;
-    }
-
-    if (is_hash(tok) &&
-        (equal(tok->next, "elif") || equal(tok->next, "else") ||
-         equal(tok->next, "endif")))
-      break;
-    tok = tok->next;
-  }
-  return tok;
-}
-
-// Double-quote a given string and returns it.
-static char *quote_string(char *str) {
-  int bufsize = 3;
-  for (int i = 0; str[i]; i++) {
-    if (str[i] == '\\' || str[i] == '"')
-      bufsize++;
-    bufsize++;
-  }
-
-  char *buf = calloc(1, bufsize);
-  char *p = buf;
-  *p++ = '"';
-  for (int i = 0; str[i]; i++) {
-    if (str[i] == '\\' || str[i] == '"')
-      *p++ = '\\';
-    *p++ = str[i];
-  }
-  *p++ = '"';
-  *p++ = '\0';
-  return buf;
-}
-
-static Token *new_str_token(char *str, Token *tmpl) {
-  char *buf = quote_string(str);
-  return tokenize(new_file(tmpl->file->name, tmpl->file->file_no, buf));
-}
-
-// Copy all tokens until the next newline, terminate them with
-// an EOF token and then returns them. This function is used to
-// create a new list of tokens for `#if` arguments.
-static Token *copy_line(Token **rest, Token *tok) {
-  Token head = {};
-  Token *cur = &head;
-
-  for (; !tok->at_bol; tok = tok->next)
-    cur = cur->next = copy_token(tok);
-
-  cur->next = new_eof(tok);
-  *rest = tok;
-  return head.next;
-}
-
-static Token *new_num_token(int val, Token *tmpl) {
-  char *buf = format("%d\n", val);
-  return tokenize(new_file(tmpl->file->name, tmpl->file->file_no, buf));
-}
-
-static Token *read_const_expr(Token **rest, Token *tok) {
-  tok = copy_line(rest, tok);
-
-  Token head = {};
-  Token *cur = &head;
-
-  while (tok->kind != TK_EOF) {
-    // "defined(foo)" or "defined foo" becomes "1" if macro "foo"
-    // is defined. Otherwise "0".
-    if (equal(tok, "defined")) {
-      Token *start = tok;
-      bool has_paren = consume(&tok, tok->next, "(");
-
-      if (tok->kind != TK_IDENT)
-        error_tok(start, "macro name must be an identifier");
-      Macro *m = find_macro(tok);
-      tok = tok->next;
-
-      if (has_paren)
-        tok = skip(tok, ")");
-
-      cur = cur->next = new_num_token(m ? 1 : 0, start);
-      continue;
-    }
-
-    cur = cur->next = tok;
-    tok = tok->next;
-  }
-
-  cur->next = tok;
-  return head.next;
-}
-
-// Read and evaluate a constant expression.
-static long eval_const_expr(Token **rest, Token *tok) {
-  Token *start = tok;
-  Token *expr = read_const_expr(rest, tok->next);
-  expr = preprocess2(expr);
-
-  if (expr->kind == TK_EOF)
-    error_tok(start, "no expression");
-
-  // [https://www.sigbus.info/n1570#6.10.1p4] The standard requires
-  // we replace remaining non-macro identifiers with "0" before
-  // evaluating a constant expression. For example, `#if foo` is
-  // equivalent to `#if 0` if foo is not defined.
-  for (Token *t = expr; t->kind != TK_EOF; t = t->next) {
-    if (t->kind == TK_IDENT) {
-      Token *next = t->next;
-      *t = *new_num_token(0, t);
-      t->next = next;
-    }
-  }
-
-  // Convert pp-numbers to regular numbers
-  convert_pp_tokens(expr);
-
-  Token *rest2;
-  long val = const_expr(&rest2, expr);
-  if (rest2->kind != TK_EOF)
-    error_tok(rest2, "extra token");
-  return val;
-}
-
-static CondIncl *push_cond_incl(Token *tok, bool included) {
-  CondIncl *ci = calloc(1, sizeof(CondIncl));
-  ci->next = cond_incl;
-  ci->ctx = IN_THEN;
-  ci->tok = tok;
-  ci->included = included;
-  cond_incl = ci;
-  return ci;
-}
-
-static Macro *find_macro(Token *tok) {
-  if (tok->kind != TK_IDENT)
-    return NULL;
-  return hashmap_get2(&macros, tok->loc, tok->len);
-}
-
-static Macro *add_macro(char *name, bool is_objlike, Token *body) {
-  Macro *m = calloc(1, sizeof(Macro));
-  m->name = name;
-  m->is_objlike = is_objlike;
-  m->body = body;
-  hashmap_put(&macros, name, m);
-  return m;
-}
-
-static MacroParam *read_macro_params(Token **rest, Token *tok, char **va_args_name) {
-  MacroParam head = {};
-  MacroParam *cur = &head;
-
-  while (!equal(tok, ")")) {
-    if (cur != &head)
-      tok = skip(tok, ",");
-
-    if (equal(tok, "...")) {
-      *va_args_name = "__VA_ARGS__";
-      *rest = skip(tok->next, ")");
-      return head.next;
-    }
-
-    if (tok->kind != TK_IDENT)
-      error_tok(tok, "expected an identifier");
-
-    if (equal(tok->next, "...")) {
-      *va_args_name = strndup(tok->loc, tok->len);
-      *rest = skip(tok->next->next, ")");
-      return head.next;
-    }
-
-    MacroParam *m = calloc(1, sizeof(MacroParam));
-    m->name = strndup(tok->loc, tok->len);
-    cur = cur->next = m;
-    tok = tok->next;
-  }
-
-  *rest = tok->next;
-  return head.next;
-}
-
-static void read_macro_definition(Token **rest, Token *tok) {
-  if (tok->kind != TK_IDENT)
-    error_tok(tok, "macro name must be an identifier");
-  char *name = strndup(tok->loc, tok->len);
-  tok = tok->next;
-
-  if (!tok->has_space && equal(tok, "(")) {
-    // Function-like macro
-    char *va_args_name = NULL;
-    MacroParam *params = read_macro_params(&tok, tok->next, &va_args_name);
-
-    Macro *m = add_macro(name, false, copy_line(rest, tok));
-    m->params = params;
-    m->va_args_name = va_args_name;
-  } else {
-    // Object-like macro
-    add_macro(name, true, copy_line(rest, tok));
-  }
-}
-
-static MacroArg *read_macro_arg_one(Token **rest, Token *tok, bool read_rest) {
-  Token head = {};
-  Token *cur = &head;
-  int level = 0;
-
-  for (;;) {
-    if (level == 0 && equal(tok, ")"))
-      break;
-    if (level == 0 && !read_rest && equal(tok, ","))
-      break;
-
-    if (tok->kind == TK_EOF)
-      error_tok(tok, "premature end of input");
-
-    if (equal(tok, "("))
-      level++;
-    else if (equal(tok, ")"))
-      level--;
-
-    cur = cur->next = copy_token(tok);
-    tok = tok->next;
-  }
-
-  cur->next = new_eof(tok);
-
-  MacroArg *arg = calloc(1, sizeof(MacroArg));
-  arg->tok = head.next;
-  *rest = tok;
-  return arg;
-}
-
-static MacroArg *
-read_macro_args(Token **rest, Token *tok, MacroParam *params, char *va_args_name) {
-  Token *start = tok;
-  tok = tok->next->next;
-
-  MacroArg head = {};
-  MacroArg *cur = &head;
-
-  MacroParam *pp = params;
-  for (; pp; pp = pp->next) {
-    if (cur != &head)
-      tok = skip(tok, ",");
-    cur = cur->next = read_macro_arg_one(&tok, tok, false);
-    cur->name = pp->name;
-  }
-
-  if (va_args_name) {
-    MacroArg *arg;
-    if (equal(tok, ")")) {
-      arg = calloc(1, sizeof(MacroArg));
-      arg->tok = new_eof(tok);
-    } else {
-      if (pp != params)
-        tok = skip(tok, ",");
-      arg = read_macro_arg_one(&tok, tok, true);
-    }
-    arg->name = va_args_name;;
-    arg->is_va_args = true;
-    cur = cur->next = arg;
-  } else if (pp) {
-    error_tok(start, "too many arguments");
-  }
-
-  skip(tok, ")");
-  *rest = tok;
-  return head.next;
-}
-
-static MacroArg *find_arg(MacroArg *args, Token *tok) {
-  for (MacroArg *ap = args; ap; ap = ap->next)
-    if (tok->len == strlen(ap->name) && !strncmp(tok->loc, ap->name, tok->len))
-      return ap;
-  return NULL;
-}
-
-// Concatenates all tokens in `tok` and returns a new string.
-static char *join_tokens(Token *tok, Token *end) {
-  // Compute the length of the resulting token.
-  int len = 1;
-  for (Token *t = tok; t != end && t->kind != TK_EOF; t = t->next) {
-    if (t != tok && t->has_space)
-      len++;
-    len += t->len;
-  }
-
-  char *buf = calloc(1, len);
-
-  // Copy token texts.
-  int pos = 0;
-  for (Token *t = tok; t != end && t->kind != TK_EOF; t = t->next) {
-    if (t != tok && t->has_space)
-      buf[pos++] = ' ';
-    strncpy(buf + pos, t->loc, t->len);
-    pos += t->len;
-  }
-  buf[pos] = '\0';
-  return buf;
-}
-
-// Concatenates all tokens in `arg` and returns a new string token.
-// This function is used for the stringizing operator (#).
-static Token *stringize(Token *hash, Token *arg) {
-  // Create a new string token. We need to set some value to its
-  // source location for error reporting function, so we use a macro
-  // name token as a template.
-  char *s = join_tokens(arg, NULL);
-  return new_str_token(s, hash);
-}
-
-// Concatenate two tokens to create a new token.
-static Token *paste(Token *lhs, Token *rhs) {
-  // Paste the two tokens.
-  char *buf = format("%.*s%.*s", lhs->len, lhs->loc, rhs->len, rhs->loc);
-
-  // Tokenize the resulting string.
-  Token *tok = tokenize(new_file(lhs->file->name, lhs->file->file_no, buf));
-  if (tok->next->kind != TK_EOF)
-    error_tok(lhs, "pasting forms '%s', an invalid token", buf);
-  return tok;
-}
-
-static bool has_varargs(MacroArg *args) {
-  for (MacroArg *ap = args; ap; ap = ap->next)
-    if (!strcmp(ap->name, "__VA_ARGS__"))
-      return ap->tok->kind != TK_EOF;
-  return false;
-}
-
-// Replace func-like macro parameters with given arguments.
-static Token *subst(Token *tok, MacroArg *args) {
-  Token head = {};
-  Token *cur = &head;
-
-  while (tok->kind != TK_EOF) {
-    // "#" followed by a parameter is replaced with stringized actuals.
-    if (equal(tok, "#")) {
-      MacroArg *arg = find_arg(args, tok->next);
-      if (!arg)
-        error_tok(tok->next, "'#' is not followed by a macro parameter");
-      cur = cur->next = stringize(tok, arg->tok);
-      tok = tok->next->next;
-      continue;
-    }
-
-    // [GNU] If __VA_ARG__ is empty, `,##__VA_ARGS__` is expanded
-    // to the empty token list. Otherwise, its expaned to `,` and
-    // __VA_ARGS__.
-    if (equal(tok, ",") && equal(tok->next, "##")) {
-      MacroArg *arg = find_arg(args, tok->next->next);
-      if (arg && arg->is_va_args) {
-        if (arg->tok->kind == TK_EOF) {
-          tok = tok->next->next->next;
-        } else {
-          cur = cur->next = copy_token(tok);
-          tok = tok->next->next;
-        }
-        continue;
-      }
-    }
-
-    if (equal(tok, "##")) {
-      if (cur == &head)
-        error_tok(tok, "'##' cannot appear at start of macro expansion");
-
-      if (tok->next->kind == TK_EOF)
-        error_tok(tok, "'##' cannot appear at end of macro expansion");
-
-      MacroArg *arg = find_arg(args, tok->next);
-      if (arg) {
-        if (arg->tok->kind != TK_EOF) {
-          *cur = *paste(cur, arg->tok);
-          for (Token *t = arg->tok->next; t->kind != TK_EOF; t = t->next)
-            cur = cur->next = copy_token(t);
-        }
-        tok = tok->next->next;
-        continue;
-      }
-
-      *cur = *paste(cur, tok->next);
-      tok = tok->next->next;
-      continue;
-    }
-
-    MacroArg *arg = find_arg(args, tok);
-
-    if (arg && equal(tok->next, "##")) {
-      Token *rhs = tok->next->next;
-
-      if (arg->tok->kind == TK_EOF) {
-        MacroArg *arg2 = find_arg(args, rhs);
-        if (arg2) {
-          for (Token *t = arg2->tok; t->kind != TK_EOF; t = t->next)
-            cur = cur->next = copy_token(t);
-        } else {
-          cur = cur->next = copy_token(rhs);
-        }
-        tok = rhs->next;
-        continue;
-      }
-
-      for (Token *t = arg->tok; t->kind != TK_EOF; t = t->next)
-        cur = cur->next = copy_token(t);
-      tok = tok->next;
-      continue;
-    }
-
-    // If __VA_ARG__ is empty, __VA_OPT__(x) is expanded to the
-    // empty token list. Otherwise, __VA_OPT__(x) is expanded to x.
-    if (equal(tok, "__VA_OPT__") && equal(tok->next, "(")) {
-      MacroArg *arg = read_macro_arg_one(&tok, tok->next->next, true);
-      if (has_varargs(args))
-        for (Token *t = arg->tok; t->kind != TK_EOF; t = t->next)
-          cur = cur->next = t;
-      tok = skip(tok, ")");
-      continue;
-    }
-
-    // Handle a macro token. Macro arguments are completely macro-expanded
-    // before they are substituted into a macro body.
-    if (arg) {
-      Token *t = preprocess2(arg->tok);
-      t->at_bol = tok->at_bol;
-      t->has_space = tok->has_space;
-      for (; t->kind != TK_EOF; t = t->next)
-        cur = cur->next = copy_token(t);
-      tok = tok->next;
-      continue;
-    }
-
-    // Handle a non-macro token.
-    cur = cur->next = copy_token(tok);
-    tok = tok->next;
-    continue;
-  }
-
-  cur->next = tok;
-  return head.next;
-}
-
-// If tok is a macro, expand it and return true.
-// Otherwise, do nothing and return false.
-static bool expand_macro(Token **rest, Token *tok) {
-  if (hideset_contains(tok->hideset, tok->loc, tok->len))
-    return false;
-
-  Macro *m = find_macro(tok);
-  if (!m)
-    return false;
-
-  // Built-in dynamic macro application such as __LINE__
-  if (m->handler) {
-    *rest = m->handler(tok);
-    (*rest)->next = tok->next;
-    return true;
-  }
-
-  // Object-like macro application
-  if (m->is_objlike) {
-    Hideset *hs = hideset_union(tok->hideset, new_hideset(m->name));
-    Token *body = add_hideset(m->body, hs);
-    for (Token *t = body; t->kind != TK_EOF; t = t->next)
-      t->origin = tok;
-    *rest = append(body, tok->next);
-    (*rest)->at_bol = tok->at_bol;
-    (*rest)->has_space = tok->has_space;
-    return true;
-  }
-
-  // If a funclike macro token is not followed by an argument list,
-  // treat it as a normal identifier.
-  if (!equal(tok->next, "("))
-    return false;
-
-  // Function-like macro application
-  Token *macro_token = tok;
-  MacroArg *args = read_macro_args(&tok, tok, m->params, m->va_args_name);
-  Token *rparen = tok;
-
-  // Tokens that consist a func-like macro invocation may have different
-  // hidesets, and if that's the case, it's not clear what the hideset
-  // for the new tokens should be. We take the interesection of the
-  // macro token and the closing parenthesis and use it as a new hideset
-  // as explained in the Dave Prossor's algorithm.
-  Hideset *hs = hideset_intersection(macro_token->hideset, rparen->hideset);
-  hs = hideset_union(hs, new_hideset(m->name));
-
-  Token *body = subst(m->body, args);
-  body = add_hideset(body, hs);
-  for (Token *t = body; t->kind != TK_EOF; t = t->next)
-    t->origin = macro_token;
-  *rest = append(body, tok->next);
-  (*rest)->at_bol = macro_token->at_bol;
-  (*rest)->has_space = macro_token->has_space;
-  return true;
-}
-
-char *search_include_paths(char *filename) {
-  if (filename[0] == '/')
-    return filename;
-
-  static HashMap cache;
-  char *cached = hashmap_get(&cache, filename);
-  if (cached)
-    return cached;
-
-  // Search a file from the include paths.
-  for (int i = 0; i < include_paths.len; i++) {
-    char *path = format("%s/%s", include_paths.data[i], filename);
-    if (!file_exists(path))
-      continue;
-    hashmap_put(&cache, filename, path);
-    include_next_idx = i + 1;
-    return path;
-  }
-  return NULL;
-}
-
-static char *search_include_next(char *filename) {
-  for (; include_next_idx < include_paths.len; include_next_idx++) {
-    char *path = format("%s/%s", include_paths.data[include_next_idx], filename);
-    if (file_exists(path))
-      return path;
-  }
-  return NULL;
-}
-
-// Read an #include argument.
-static char *read_include_filename(Token **rest, Token *tok, bool *is_dquote) {
-  // Pattern 1: #include "foo.h"
-  if (tok->kind == TK_STR) {
-    // A double-quoted filename for #include is a special kind of
-    // token, and we don't want to interpret any escape sequences in it.
-    // For example, "\f" in "C:\foo" is not a formfeed character but
-    // just two non-control characters, backslash and f.
-    // So we don't want to use token->str.
-    *is_dquote = true;
-    *rest = skip_line(tok->next);
-    return strndup(tok->loc + 1, tok->len - 2);
-  }
-
-  // Pattern 2: #include <foo.h>
-  if (equal(tok, "<")) {
-    // Reconstruct a filename from a sequence of tokens between
-    // "<" and ">".
-    Token *start = tok;
-
-    // Find closing ">".
-    for (; !equal(tok, ">"); tok = tok->next)
-      if (tok->at_bol || tok->kind == TK_EOF)
-        error_tok(tok, "expected '>'");
-
-    *is_dquote = false;
-    *rest = skip_line(tok->next);
-    return join_tokens(start->next, tok);
-  }
-
-  // Pattern 3: #include FOO
-  // In this case FOO must be macro-expanded to either
-  // a single string token or a sequence of "<" ... ">".
-  if (tok->kind == TK_IDENT) {
-    Token *tok2 = preprocess2(copy_line(rest, tok));
-    return read_include_filename(&tok2, tok2, is_dquote);
-  }
-
-  error_tok(tok, "expected a filename");
-}
-
-// Detect the following "include guard" pattern.
-//
-//   #ifndef FOO_H
-//   #define FOO_H
-//   ...
-//   #endif
-static char *detect_include_guard(Token *tok) {
-  // Detect the first two lines.
-  if (!is_hash(tok) || !equal(tok->next, "ifndef"))
-    return NULL;
-  tok = tok->next->next;
-
-  if (tok->kind != TK_IDENT)
-    return NULL;
-
-  char *macro = strndup(tok->loc, tok->len);
-  tok = tok->next;
-
-  if (!is_hash(tok) || !equal(tok->next, "define") || !equal(tok->next->next, macro))
-    return NULL;
-
-  // Read until the end of the file.
-  while (tok->kind != TK_EOF) {
-    if (!is_hash(tok)) {
-      tok = tok->next;
-      continue;
-    }
-
-    if (equal(tok->next, "endif") && tok->next->next->kind == TK_EOF)
-      return macro;
-
-    if (equal(tok, "if") || equal(tok, "ifdef") || equal(tok, "ifndef"))
-      tok = skip_cond_incl(tok->next);
-    else
-      tok = tok->next;
-  }
-  return NULL;
-}
-
-static Token *include_file(Token *tok, char *path, Token *filename_tok) {
-  // Check for "#pragma once"
-  if (hashmap_get(&pragma_once, path))
-    return tok;
-
-  // If we read the same file before, and if the file was guarded
-  // by the usual #ifndef ... #endif pattern, we may be able to
-  // skip the file without opening it.
-  static HashMap include_guards;
-  char *guard_name = hashmap_get(&include_guards, path);
-  if (guard_name && hashmap_get(&macros, guard_name))
-    return tok;
-
-  Token *tok2 = tokenize_file(path);
-  if (!tok2)
-    error_tok(filename_tok, "%s: cannot open file: %s", path, strerror(errno));
-
-  guard_name = detect_include_guard(tok2);
-  if (guard_name)
-    hashmap_put(&include_guards, path, guard_name);
-
-  return append(tok2, tok);
-}
-
-// Read #line arguments
-static void read_line_marker(Token **rest, Token *tok) {
-  Token *start = tok;
-  tok = preprocess(copy_line(rest, tok));
-
-  if (tok->kind != TK_NUM || tok->ty->kind != TY_INT)
-    error_tok(tok, "invalid line marker");
-  start->file->line_delta = tok->val - start->line_no;
-
-  tok = tok->next;
-  if (tok->kind == TK_EOF)
-    return;
-
-  if (tok->kind != TK_STR)
-    error_tok(tok, "filename expected");
-  start->file->display_name = tok->str;
-}
-
-// Visit all tokens in `tok` while evaluating preprocessing
-// macros and directives.
-static Token *preprocess2(Token *tok) {
-  Token head = {};
-  Token *cur = &head;
-
-  while (tok->kind != TK_EOF) {
-    // If it is a macro, expand it.
-    if (expand_macro(&tok, tok))
-      continue;
-
-    // Pass through if it is not a "#".
-    if (!is_hash(tok)) {
-      tok->line_delta = tok->file->line_delta;
-      tok->filename = tok->file->display_name;
-      cur = cur->next = tok;
-      tok = tok->next;
-      continue;
-    }
-
-    Token *start = tok;
-    tok = tok->next;
-
-    if (equal(tok, "include")) {
-      bool is_dquote;
-      char *filename = read_include_filename(&tok, tok->next, &is_dquote);
-
-      if (filename[0] != '/' && is_dquote) {
-        char *path = format("%s/%s", dirname(strdup(start->file->name)), filename);
-        if (file_exists(path)) {
-          tok = include_file(tok, path, start->next->next);
-          continue;
-        }
-      }
-
-      char *path = search_include_paths(filename);
-      tok = include_file(tok, path ? path : filename, start->next->next);
-      continue;
-    }
-
-    if (equal(tok, "include_next")) {
-      bool ignore;
-      char *filename = read_include_filename(&tok, tok->next, &ignore);
-      char *path = search_include_next(filename);
-      tok = include_file(tok, path ? path : filename, start->next->next);
-      continue;
-    }
-
-    if (equal(tok, "define")) {
-      read_macro_definition(&tok, tok->next);
-      continue;
-    }
-
-    if (equal(tok, "undef")) {
-      tok = tok->next;
-      if (tok->kind != TK_IDENT)
-        error_tok(tok, "macro name must be an identifier");
-      undef_macro(strndup(tok->loc, tok->len));
-      tok = skip_line(tok->next);
-      continue;
-    }
-
-    if (equal(tok, "if")) {
-      long val = eval_const_expr(&tok, tok);
-      push_cond_incl(start, val);
-      if (!val)
-        tok = skip_cond_incl(tok);
-      continue;
-    }
-
-    if (equal(tok, "ifdef")) {
-      bool defined = find_macro(tok->next);
-      push_cond_incl(tok, defined);
-      tok = skip_line(tok->next->next);
-      if (!defined)
-        tok = skip_cond_incl(tok);
-      continue;
-    }
-
-    if (equal(tok, "ifndef")) {
-      bool defined = find_macro(tok->next);
-      push_cond_incl(tok, !defined);
-      tok = skip_line(tok->next->next);
-      if (defined)
-        tok = skip_cond_incl(tok);
-      continue;
-    }
-
-    if (equal(tok, "elif")) {
-      if (!cond_incl || cond_incl->ctx == IN_ELSE)
-        error_tok(start, "stray #elif");
-      cond_incl->ctx = IN_ELIF;
-
-      if (!cond_incl->included && eval_const_expr(&tok, tok))
-        cond_incl->included = true;
-      else
-        tok = skip_cond_incl(tok);
-      continue;
-    }
-
-    if (equal(tok, "else")) {
-      if (!cond_incl || cond_incl->ctx == IN_ELSE)
-        error_tok(start, "stray #else");
-      cond_incl->ctx = IN_ELSE;
-      tok = skip_line(tok->next);
-
-      if (cond_incl->included)
-        tok = skip_cond_incl(tok);
-      continue;
-    }
-
-    if (equal(tok, "endif")) {
-      if (!cond_incl)
-        error_tok(start, "stray #endif");
-      cond_incl = cond_incl->next;
-      tok = skip_line(tok->next);
-      continue;
-    }
-
-    if (equal(tok, "line")) {
-      read_line_marker(&tok, tok->next);
-      continue;
-    }
-
-    if (tok->kind == TK_PP_NUM) {
-      read_line_marker(&tok, tok);
-      continue;
-    }
-
-    if (equal(tok, "pragma") && equal(tok->next, "once")) {
-      hashmap_put(&pragma_once, tok->file->name, (void *)1);
-      tok = skip_line(tok->next->next);
-      continue;
-    }
-
-    if (equal(tok, "pragma")) {
-      do {
-        tok = tok->next;
-      } while (!tok->at_bol);
-      continue;
-    }
-
-    if (equal(tok, "error"))
-      error_tok(tok, "error");
-
-    // `#`-only line is legal. It's called a null directive.
-    if (tok->at_bol)
-      continue;
-
-    error_tok(tok, "invalid preprocessor directive");
-  }
-
-  cur->next = tok;
-  return head.next;
-}
-
-void define_macro(char *name, char *buf) {
-  Token *tok = tokenize(new_file("<built-in>", 1, buf));
-  add_macro(name, true, tok);
-}
-
-void undef_macro(char *name) {
-  hashmap_delete(&macros, name);
-}
-
-static Macro *add_builtin(char *name, macro_handler_fn *fn) {
-  Macro *m = add_macro(name, true, NULL);
-  m->handler = fn;
-  return m;
-}
-
-static Token *file_macro(Token *tmpl) {
-  while (tmpl->origin)
-    tmpl = tmpl->origin;
-  return new_str_token(tmpl->file->display_name, tmpl);
-}
-
-static Token *line_macro(Token *tmpl) {
-  while (tmpl->origin)
-    tmpl = tmpl->origin;
-  int i = tmpl->line_no + tmpl->file->line_delta;
-  return new_num_token(i, tmpl);
-}
-
-// __COUNTER__ is expanded to serial values starting from 0.
-static Token *counter_macro(Token *tmpl) {
-  static int i = 0;
-  return new_num_token(i++, tmpl);
-}
-
-// __TIMESTAMP__ is expanded to a string describing the last
-// modification time of the current file. E.g.
-// "Fri Jul 24 01:32:50 2020"
-static Token *timestamp_macro(Token *tmpl) {
-  struct stat st;
-  if (stat(tmpl->file->name, &st) != 0)
-    return new_str_token("??? ??? ?? ??:??:?? ????", tmpl);
-
-  char buf[30];
-  ctime_r(&st.st_mtime, buf);
-  buf[24] = '\0';
-  return new_str_token(buf, tmpl);
-}
-
-static Token *base_file_macro(Token *tmpl) {
-  return new_str_token(base_file, tmpl);
-}
-
-// __DATE__ is expanded to the current date, e.g. "May 17 2020".
-static char *format_date(struct tm *tm) {
-  static char mon[][4] = {
-    "Jan", "Feb", "Mar", "Apr", "May", "Jun",
-    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
-  };
-
-  return format("\"%s %2d %d\"", mon[tm->tm_mon], tm->tm_mday, tm->tm_year + 1900);
-}
-
-// __TIME__ is expanded to the current time, e.g. "13:34:03".
-static char *format_time(struct tm *tm) {
-  return format("\"%02d:%02d:%02d\"", tm->tm_hour, tm->tm_min, tm->tm_sec);
-}
-
-void init_macros(void) {
-  // Define predefined macros
-  define_macro("_LP64", "1");
-  define_macro("__C99_MACRO_WITH_VA_ARGS", "1");
-  define_macro("__ELF__", "1");
-  define_macro("__LP64__", "1");
-  define_macro("__SIZEOF_DOUBLE__", "8");
-  define_macro("__SIZEOF_FLOAT__", "4");
-  define_macro("__SIZEOF_INT__", "4");
-  define_macro("__SIZEOF_LONG_DOUBLE__", "8");
-  define_macro("__SIZEOF_LONG_LONG__", "8");
-  define_macro("__SIZEOF_LONG__", "8");
-  define_macro("__SIZEOF_POINTER__", "8");
-  define_macro("__SIZEOF_PTRDIFF_T__", "8");
-  define_macro("__SIZEOF_SHORT__", "2");
-  define_macro("__SIZEOF_SIZE_T__", "8");
-  define_macro("__SIZE_TYPE__", "unsigned long");
-  define_macro("__STDC_HOSTED__", "1");
-  define_macro("__STDC_NO_COMPLEX__", "1");
-  define_macro("__STDC_UTF_16__", "1");
-  define_macro("__STDC_UTF_32__", "1");
-  define_macro("__STDC_VERSION__", "201112L");
-  define_macro("__STDC__", "1");
-  define_macro("__USER_LABEL_PREFIX__", "");
-  define_macro("__alignof__", "_Alignof");
-  define_macro("__amd64", "1");
-  define_macro("__amd64__", "1");
-  define_macro("__chibicc__", "1");
-  define_macro("__const__", "const");
-  define_macro("__gnu_linux__", "1");
-  define_macro("__inline__", "inline");
-  define_macro("__linux", "1");
-  define_macro("__linux__", "1");
-  define_macro("__signed__", "signed");
-  define_macro("__typeof__", "typeof");
-  define_macro("__unix", "1");
-  define_macro("__unix__", "1");
-  define_macro("__volatile__", "volatile");
-  define_macro("__x86_64", "1");
-  define_macro("__x86_64__", "1");
-  define_macro("linux", "1");
-  define_macro("unix", "1");
-
-  add_builtin("__FILE__", file_macro);
-  add_builtin("__LINE__", line_macro);
-  add_builtin("__COUNTER__", counter_macro);
-  add_builtin("__TIMESTAMP__", timestamp_macro);
-  add_builtin("__BASE_FILE__", base_file_macro);
-
-  time_t now = time(NULL);
-  struct tm *tm = localtime(&now);
-  define_macro("__DATE__", format_date(tm));
-  define_macro("__TIME__", format_time(tm));
-}
-
-typedef enum {
-  STR_NONE, STR_UTF8, STR_UTF16, STR_UTF32, STR_WIDE,
-} StringKind;
-
-static StringKind getStringKind(Token *tok) {
-  if (!strcmp(tok->loc, "u8"))
-    return STR_UTF8;
-
-  switch (tok->loc[0]) {
-  case '"': return STR_NONE;
-  case 'u': return STR_UTF16;
-  case 'U': return STR_UTF32;
-  case 'L': return STR_WIDE;
-  }
-  unreachable();
-}
-
-// Concatenate adjacent string literals into a single string literal
-// as per the C spec.
-static void join_adjacent_string_literals(Token *tok) {
-  // First pass: If regular string literals are adjacent to wide
-  // string literals, regular string literals are converted to a wide
-  // type before concatenation. In this pass, we do the conversion.
-  for (Token *tok1 = tok; tok1->kind != TK_EOF;) {
-    if (tok1->kind != TK_STR || tok1->next->kind != TK_STR) {
-      tok1 = tok1->next;
-      continue;
-    }
-
-    StringKind kind = getStringKind(tok1);
-    Type *basety = tok1->ty->base;
-
-    for (Token *t = tok1->next; t->kind == TK_STR; t = t->next) {
-      StringKind k = getStringKind(t);
-      if (kind == STR_NONE) {
-        kind = k;
-        basety = t->ty->base;
-      } else if (k != STR_NONE && kind != k) {
-        error_tok(t, "unsupported non-standard concatenation of string literals");
-      }
-    }
-
-    if (basety->size > 1)
-      for (Token *t = tok1; t->kind == TK_STR; t = t->next)
-        if (t->ty->base->size == 1)
-          *t = *tokenize_string_literal(t, basety);
-
-    while (tok1->kind == TK_STR)
-      tok1 = tok1->next;
-  }
-
-  // Second pass: concatenate adjacent string literals.
-  for (Token *tok1 = tok; tok1->kind != TK_EOF;) {
-    if (tok1->kind != TK_STR || tok1->next->kind != TK_STR) {
-      tok1 = tok1->next;
-      continue;
-    }
-
-    Token *tok2 = tok1->next;
-    while (tok2->kind == TK_STR)
-      tok2 = tok2->next;
-
-    int len = tok1->ty->array_len;
-    for (Token *t = tok1->next; t != tok2; t = t->next)
-      len = len + t->ty->array_len - 1;
-
-    char *buf = calloc(tok1->ty->base->size, len);
-
-    int i = 0;
-    for (Token *t = tok1; t != tok2; t = t->next) {
-      memcpy(buf + i, t->str, t->ty->size);
-      i = i + t->ty->size - t->ty->base->size;
-    }
-
-    *tok1 = *copy_token(tok1);
-    tok1->ty = array_of(tok1->ty->base, len);
-    tok1->str = buf;
-    tok1->next = tok2;
-    tok1 = tok2;
-  }
-}
-
-// Entry point function of the preprocessor.
-Token *preprocess(Token *tok) {
-  tok = preprocess2(tok);
-  if (cond_incl)
-    error_tok(cond_incl->tok, "unterminated conditional directive");
-  convert_pp_tokens(tok);
-  join_adjacent_string_literals(tok);
-
-  for (Token *t = tok; t; t = t->next)
-    t->line_no += t->line_delta;
-  return tok;
-}
-- 
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