diff --git a/core/c/frontend/preprocessor/const_expr.odin b/core/c/frontend/preprocessor/const_expr.odin
new file mode 100644
index 000000000..5f52fff9c
--- /dev/null
+++ b/core/c/frontend/preprocessor/const_expr.odin
@@ -0,0 +1,25 @@
+package c_frontend_preprocess
+
+import "core:c/frontend/tokenizer"
+
+const_expr :: proc(rest: ^^Token, tok: ^Token) -> i64 {
+	// TODO(bill): Handle const_expr correctly
+	// This is effectively a mini-parser
+
+	assert(rest != nil);
+	assert(tok != nil);
+	rest^ = tokenizer.new_eof(tok);
+	switch v in tok.val {
+	case i64:
+		return v;
+	case f64:
+		return i64(v);
+	case string:
+		return 0;
+	case []u16:
+		// TODO
+	case []u32:
+		// TODO
+	}
+	return 0;
+}
diff --git a/core/c/frontend/preprocessor/preprocess.odin b/core/c/frontend/preprocessor/preprocess.odin
new file mode 100644
index 000000000..3af2c2339
--- /dev/null
+++ b/core/c/frontend/preprocessor/preprocess.odin
@@ -0,0 +1,1498 @@
+package c_frontend_preprocess
+
+import "../tokenizer"
+
+import "core:strings"
+import "core:strconv"
+import "core:path/filepath"
+import "core:unicode/utf8"
+import "core:unicode/utf16"
+import "core:os"
+
+@(private)
+Tokenizer :: tokenizer.Tokenizer;
+@(private)
+Token :: tokenizer.Token;
+
+Error_Handler :: tokenizer.Error_Handler;
+
+Macro_Param :: struct {
+	next: ^Macro_Param,
+	name: string,
+}
+
+Macro_Arg :: struct {
+	next: ^Macro_Arg,
+	name: string,
+	tok: ^Token,
+	is_va_args: bool,
+}
+
+Macro_Kind :: enum u8 {
+	Function_Like,
+	Value_Like,
+}
+
+Macro_Handler :: #type proc(^Preprocessor, ^Token) -> ^Token;
+
+Macro :: struct {
+	name: string,
+	kind: Macro_Kind,
+	params: ^Macro_Param,
+	va_args_name: string,
+	body: ^Token,
+	handler: Macro_Handler,
+}
+
+Cond_Incl_State :: enum u8 {
+	In_Then,
+	In_Elif,
+	In_Else,
+}
+
+Cond_Incl :: struct {
+	next: ^Cond_Incl,
+	tok:  ^Token,
+	state:    Cond_Incl_State,
+	included: bool,
+}
+
+Pragma_Handler :: #type proc(^Preprocessor, ^Token);
+
+Preprocessor :: struct {
+	// Lookup tables
+	macros:         map[string]^Macro,
+	pragma_once:    map[string]bool,
+	include_guards: map[string]string,
+	filepath_cache: map[string]string,
+
+	// Include path data
+	include_paths: []string,
+
+	// Counter for __COUNTER__ macro
+	counter: i64,
+
+	// Include information
+	cond_incl: ^Cond_Incl,
+	include_level: int,
+	include_next_index: int,
+
+	wide_char_size: int,
+
+	// Mutable data
+	err:  Error_Handler,
+	warn: Error_Handler,
+	pragma_handler: Pragma_Handler,
+	error_count:   int,
+	warning_count: int,
+}
+
+MAX_INCLUDE_LEVEL :: 1024;
+
+error :: proc(cpp: ^Preprocessor, tok: ^Token, msg: string, args: ..any) {
+	if cpp.err != nil {
+		cpp.err(tok.pos, msg, ..args);
+	}
+	cpp.error_count += 1;
+}
+
+warn :: proc(cpp: ^Preprocessor, tok: ^Token, msg: string, args: ..any) {
+	if cpp.warn != nil {
+		cpp.warn(tok.pos, msg, ..args);
+	}
+	cpp.warning_count += 1;
+}
+
+is_hash :: proc(tok: ^Token) -> bool {
+	return tok.at_bol && tok.lit == "#";
+}
+
+skip_line :: proc(cpp: ^Preprocessor, tok: ^Token) -> ^Token {
+	tok := tok;
+	if tok.at_bol {
+		return tok;
+	}
+	warn(cpp, tok, "extra token");
+	for tok.at_bol {
+		tok = tok.next;
+	}
+	return tok;
+}
+
+
+append_token :: proc(a, b: ^Token) -> ^Token {
+	if a.kind == .EOF {
+		return b;
+	}
+
+	head: Token;
+	curr := &head;
+
+	for tok := a; tok.kind != .EOF; tok = tok.next {
+		curr.next = tokenizer.copy_token(tok);
+		curr = curr.next;
+	}
+	curr.next = b;
+	return head.next;
+}
+
+
+is_hex_digit :: proc(x: byte) -> bool {
+	switch x {
+	case '0'..'9', 'a'..'f', 'A'..'F':
+		return true;
+	}
+	return false;
+}
+from_hex :: proc(x: byte) -> i32 {
+	switch x {
+	case '0'..'9':
+		return i32(x) - '0';
+	case 'a'..'f':
+		return i32(x) - 'a' + 10;
+	case 'A'..'F':
+		return i32(x) - 'A' + 10;
+	}
+	return 16;
+}
+
+
+convert_pp_number :: proc(tok: ^Token) {
+	convert_pp_int :: proc(tok: ^Token) -> bool {
+		p := tok.lit;
+		base := 10;
+		if len(p) > 2 {
+			if strings.equal_fold(p[:2], "0x") && is_hex_digit(p[2]) {
+				p = p[2:];
+				base = 16;
+			} else if strings.equal_fold(p[:2], "0b") && p[2] == '0' || p[2] == '1' {
+				p = p[2:];
+				base = 2;
+			}
+		}
+		if base == 10 && p[0] == '0' {
+			base = 8;
+		}
+
+
+		tok.val, _ = strconv.parse_i64_of_base(p, base);
+
+		l, u: int;
+
+		suf: [3]byte;
+		suf_n := 0;
+		i := len(p)-1;
+		for /**/; i >= 0 && suf_n < len(suf); i -= 1 {
+			switch p[i] {
+			case 'l', 'L':
+				suf[suf_n] = 'l';
+				l += 1;
+				suf_n += 1;
+			case 'u', 'U':
+				suf[suf_n] = 'u';
+				u += 1;
+				suf_n += 1;
+			}
+		}
+		if i < len(p) {
+			if !is_hex_digit(p[i]) && p[i] != '.' {
+				return false;
+			}
+		}
+		if u > 1 {
+			return false;
+		}
+
+		if l > 2 {
+			return false;
+		}
+
+		if u == 1 {
+			switch l {
+			case 0: tok.type_hint = .Unsigned_Int;
+			case 1: tok.type_hint = .Unsigned_Long;
+			case 2: tok.type_hint = .Unsigned_Long_Long;
+			}
+		} else {
+			switch l {
+			case 0: tok.type_hint = .Int;
+			case 1: tok.type_hint = .Long;
+			case 2: tok.type_hint = .Long_Long;
+			}
+		}
+		return true;
+	}
+
+	if convert_pp_int(tok) {
+		return;
+	}
+
+	fval, _ := strconv.parse_f64(tok.lit);
+	tok.val = fval;
+
+	end := tok.lit[len(tok.lit)-1];
+	switch end {
+	case 'f', 'F':
+		tok.type_hint = .Float;
+	case 'l', 'L':
+		tok.type_hint = .Long_Double;
+	case:
+		tok.type_hint = .Double;
+	}
+
+}
+
+convert_pp_char :: proc(tok: ^Token) {
+	assert(len(tok.lit) >= 2);
+	r, _, _, _ := unquote_char(tok.lit, tok.lit[0]);
+	tok.val = i64(r);
+
+	tok.type_hint = .Int;
+	switch tok.prefix {
+	case "u": tok.type_hint = .UTF_16;
+	case "U": tok.type_hint = .UTF_32;
+	case "L": tok.type_hint = .UTF_Wide;
+	}
+}
+
+wide_char_size :: proc(cpp: ^Preprocessor) -> int {
+	char_size := 4;
+	if cpp.wide_char_size > 0 {
+		char_size = clamp(cpp.wide_char_size, 1, 4);
+		assert(char_size & (char_size-1) == 0);
+	}
+	return char_size;
+}
+
+convert_pp_string :: proc(cpp: ^Preprocessor, tok: ^Token) {
+	assert(len(tok.lit) >= 2);
+	str, _, _ := unquote_string(tok.lit);
+	tok.val = str;
+
+	char_size := 1;
+
+	switch tok.prefix {
+	case "u8":
+		tok.type_hint = .UTF_8;
+		char_size = 1;
+	case "u":
+		tok.type_hint = .UTF_16;
+		char_size = 2;
+	case "U":
+		tok.type_hint = .UTF_32;
+		char_size = 4;
+	case "L":
+		tok.type_hint = .UTF_Wide;
+		char_size = wide_char_size(cpp);
+	}
+
+	switch char_size {
+	case 2:
+		n: int;
+		buf := make([]u16, len(str));
+		for c in str {
+			ch := c;
+			if ch < 0x10000 {
+				buf[n] = u16(ch);
+				n += 1;
+			} else {
+				ch -= 0x10000;
+				buf[n+0] = 0xd800 + u16((ch >> 10) & 0x3ff);
+				buf[n+1] = 0xdc00 + u16(ch & 0x3ff);
+				n += 2;
+			}
+		}
+		tok.val = buf[:n];
+	case 4:
+		n: int;
+		buf := make([]u32, len(str));
+		for ch in str {
+			buf[n] = u32(ch);
+			n += 1;
+		}
+		tok.val = buf[:n];
+	}
+
+}
+
+convert_pp_token :: proc(cpp: ^Preprocessor, t: ^Token, is_keyword: tokenizer.Is_Keyword_Proc) {
+	switch {
+	case t.kind == .Char:
+		convert_pp_char(t);
+	case t.kind == .String:
+		convert_pp_string(cpp, t);
+	case is_keyword != nil && is_keyword(t):
+		t.kind = .Keyword;
+	case t.kind == .PP_Number:
+		convert_pp_number(t);
+	}
+}
+convert_pp_tokens :: proc(cpp: ^Preprocessor, tok: ^Token, is_keyword: tokenizer.Is_Keyword_Proc) {
+	for t := tok; t != nil && t.kind != .EOF; t = t.next {
+		convert_pp_token(cpp, tok, is_keyword);
+	}
+}
+
+join_adjacent_string_literals :: proc(cpp: ^Preprocessor, initial_tok: ^Token) {
+	for tok1 := initial_tok; tok1.kind != .EOF; /**/ {
+		if tok1.kind != .String || tok1.next.kind != .String {
+			tok1 = tok1.next;
+			continue;
+		}
+
+		type_hint := tokenizer.Token_Type_Hint.None;
+		char_size := 1;
+
+		start := tok1;
+		for t := tok1; t != nil && t.kind == .String; t = t.next {
+			if t.val == nil {
+				convert_pp_string(cpp, t);
+			}
+			tok1 = t.next;
+			if type_hint != t.type_hint {
+				if t.type_hint != .None && type_hint != .None {
+					error(cpp, t, "unsupported non-standard concatenation of string literals of different types");
+				}
+				prev_char_size := char_size;
+
+				#partial switch type_hint {
+				case .UTF_8:    char_size = max(char_size, 1);
+				case .UTF_16:   char_size = max(char_size, 2);
+				case .UTF_32:   char_size = max(char_size, 4);
+				case .UTF_Wide: char_size = max(char_size, wide_char_size(cpp));
+				}
+
+				if type_hint == .None || prev_char_size < char_size {
+					type_hint = t.type_hint;
+				}
+			}
+		}
+
+		// NOTE(bill): Verbose logic in order to correctly concantenate strings, even if they different in type
+		max_len := 0;
+		switch char_size {
+		case 1:
+			for t := start; t != nil && t.kind == .String; t = t.next {
+				#partial switch v in t.val {
+				case string: max_len += len(v);
+				case []u16:  max_len += 2*len(v);
+				case []u32:  max_len += 4*len(v);
+				}
+			}
+			n := 0;
+			buf := make([]byte, max_len);
+			for t := start; t != nil && t.kind == .String; t = t.next {
+				#partial switch v in t.val {
+				case string:
+					n += copy(buf[n:], v);
+				case []u16:
+					for i := 0; i < len(v); /**/ {
+						c1 := v[i];
+						r: rune;
+						if !utf16.is_surrogate(rune(c1)) {
+							r = rune(c1);
+							i += 1;
+						} else if i+1 == len(v) {
+							r = utf16.REPLACEMENT_CHAR;
+							i += 1;
+						} else {
+							c2 := v[i+1];
+							i += 2;
+							r = utf16.decode_surrogate_pair(rune(c1), rune(c2));
+						}
+
+						b, w := utf8.encode_rune(r);
+						n += copy(buf[n:], b[:w]);
+					}
+				case []u32:
+					for r in v {
+						b, w := utf8.encode_rune(rune(r));
+						n += copy(buf[n:], b[:w]);
+					}
+				}
+			}
+
+			new_tok := tokenizer.copy_token(start);
+			new_tok.lit = "";
+			new_tok.val = string(buf[:n]);
+			new_tok.next = tok1;
+			new_tok.type_hint = type_hint;
+			start^ = new_tok^;
+		case 2:
+			for t := start; t != nil && t.kind == .String; t = t.next {
+				#partial switch v in t.val {
+				case string: max_len += len(v);
+				case []u16:  max_len += len(v);
+				case []u32:  max_len += 2*len(v);
+				}
+			}
+			n := 0;
+			buf := make([]u16, max_len);
+			for t := start; t != nil && t.kind == .String; t = t.next {
+				#partial switch v in t.val {
+				case string:
+					for r in v {
+						if r >= 0x10000 {
+							c1, c2 := utf16.encode_surrogate_pair(r);
+							buf[n+0] = u16(c1);
+							buf[n+1] = u16(c2);
+							n += 2;
+						} else {
+							buf[n] = u16(r);
+							n += 1;
+						}
+					}
+				case []u16:
+					n += copy(buf[n:], v);
+				case []u32:
+					for r in v {
+						if r >= 0x10000 {
+							c1, c2 := utf16.encode_surrogate_pair(rune(r));
+							buf[n+0] = u16(c1);
+							buf[n+1] = u16(c2);
+							n += 2;
+						} else {
+							buf[n] = u16(r);
+							n += 1;
+						}
+					}
+				}
+			}
+
+			new_tok := tokenizer.copy_token(start);
+			new_tok.lit = "";
+			new_tok.val = buf[:n];
+			new_tok.next = tok1;
+			new_tok.type_hint = type_hint;
+			start^ = new_tok^;
+		case 4:
+			for t := start; t != nil && t.kind == .String; t = t.next {
+				#partial switch v in t.val {
+				case string: max_len += len(v);
+				case []u16:  max_len += len(v);
+				case []u32:  max_len += len(v);
+				}
+			}
+			n := 0;
+			buf := make([]u32, max_len);
+			for t := start; t != nil && t.kind == .String; t = t.next {
+				#partial switch v in t.val {
+				case string:
+					for r in v {
+						buf[n] = u32(r);
+						n += 1;
+					}
+				case []u16:
+					for i := 0; i < len(v); /**/ {
+						c1 := v[i];
+						if !utf16.is_surrogate(rune(c1)) {
+							buf[n] = u32(c1);
+							n += 1;
+							i += 1;
+						} else if i+1 == len(v) {
+							buf[n] = utf16.REPLACEMENT_CHAR;
+							n += 1;
+							i += 1;
+						} else {
+							c2 := v[i+1];
+							i += 2;
+							r := utf16.decode_surrogate_pair(rune(c1), rune(c2));
+							buf[n] = u32(r);
+							n += 1;
+						}
+					}
+				case []u32:
+					n += copy(buf[n:], v);
+				}
+			}
+
+			new_tok := tokenizer.copy_token(start);
+			new_tok.lit = "";
+			new_tok.val = buf[:n];
+			new_tok.next = tok1;
+			new_tok.type_hint = type_hint;
+			start^ = new_tok^;
+		}
+	}
+}
+
+
+quote_string :: proc(s: string) -> []byte {
+	b := &strings.Builder{};
+	strings.init_builder(b, 0, len(s)+2);
+	strings.write_quoted_string(b, s, '"');
+	return b.buf[:];
+}
+
+
+_init_tokenizer_from_preprocessor :: proc(t: ^Tokenizer, cpp: ^Preprocessor) -> ^Tokenizer {
+	t.warn = cpp.warn;
+	t.err = cpp.err;
+	return t;
+}
+
+new_string_token :: proc(cpp: ^Preprocessor, str: string, tok: ^Token) -> ^Token {
+	assert(tok != nil);
+	assert(str != "");
+	t := _init_tokenizer_from_preprocessor(&Tokenizer{}, cpp);
+	src := quote_string(str);
+	return tokenizer.inline_tokenize(t, tok, src);
+}
+
+stringize :: proc(cpp: ^Preprocessor, hash, arg: ^Token) -> ^Token {
+	s := join_tokens(arg, nil);
+	return new_string_token(cpp, s, hash);
+}
+
+
+new_number_token :: proc(cpp: ^Preprocessor, i: i64, tok: ^Token) -> ^Token {
+	t := _init_tokenizer_from_preprocessor(&Tokenizer{}, cpp);
+	buf: [32]byte;
+	n := len(strconv.append_int(buf[:], i, 10));
+	src := make([]byte, n);
+	copy(src, buf[:n]);
+	return tokenizer.inline_tokenize(t, tok, src);
+}
+
+
+find_macro :: proc(cpp: ^Preprocessor, tok: ^Token) -> ^Macro {
+	if tok.kind != .Ident {
+		return nil;
+	}
+	return cpp.macros[tok.lit];
+}
+
+add_macro :: proc(cpp: ^Preprocessor, name: string, kind: Macro_Kind, body: ^Token) -> ^Macro {
+	m := new(Macro);
+	m.name = name;
+	m.kind = kind;
+	m.body = body;
+	cpp.macros[name] = m;
+	return m;
+}
+
+
+undef_macro :: proc(cpp: ^Preprocessor, name: string) {
+	delete_key(&cpp.macros, name);
+}
+
+add_builtin :: proc(cpp: ^Preprocessor, name: string, handler: Macro_Handler) -> ^Macro {
+	m := add_macro(cpp, name, .Value_Like, nil);
+	m.handler = handler;
+	return m;
+}
+
+
+skip :: proc(cpp: ^Preprocessor, tok: ^Token, op: string) -> ^Token {
+	if tok.lit != op {
+		error(cpp, tok, "expected '%q'", op);
+	}
+	return tok.next;
+}
+
+consume :: proc(rest: ^^Token, tok: ^Token, lit: string) -> bool {
+	if tok.lit == lit {
+		rest^ = tok.next;
+		return true;
+	}
+	rest^ = tok;
+	return false;
+}
+
+read_macro_params :: proc(cpp: ^Preprocessor, rest: ^^Token, tok: ^Token) -> (param: ^Macro_Param, va_args_name: string) {
+	head: Macro_Param;
+	curr := &head;
+
+	tok := tok;
+	for tok.lit != ")" && tok.kind != .EOF {
+		if curr != &head {
+			tok = skip(cpp, tok, ",");
+		}
+
+		if tok.lit == "..." {
+			va_args_name = "__VA_ARGS__";
+			rest^ = skip(cpp, tok.next, ")");
+			param = head.next;
+			return;
+		}
+
+		if tok.kind != .Ident {
+			error(cpp, tok, "expected an identifier");
+		}
+
+		if tok.next.lit == "..." {
+			va_args_name = tok.lit;
+			rest^ = skip(cpp, tok.next.next, ")");
+			param = head.next;
+			return;
+		}
+
+		m := new(Macro_Param);
+		m.name = tok.lit;
+		curr.next = m;
+		curr = curr.next;
+		tok = tok.next;
+	}
+
+
+	rest^ = tok.next;
+	param = head.next;
+	return;
+}
+
+copy_line :: proc(rest: ^^Token, tok: ^Token) -> ^Token {
+	head: Token;
+	curr := &head;
+
+	tok := tok;
+	for ; !tok.at_bol; tok = tok.next {
+		curr.next = tokenizer.copy_token(tok);
+		curr = curr.next;
+	}
+	curr.next = tokenizer.new_eof(tok);
+	rest^ = tok;
+	return head.next;
+}
+
+read_macro_definition :: proc(cpp: ^Preprocessor, rest: ^^Token, tok: ^Token) {
+	tok := tok;
+	if tok.kind != .Ident {
+		error(cpp, tok, "macro name must be an identifier");
+	}
+	name := tok.lit;
+	tok = tok.next;
+
+	if !tok.has_space && tok.lit == "(" {
+		params, va_args_name := read_macro_params(cpp, &tok, tok.next);
+
+		m := add_macro(cpp, name, .Function_Like, copy_line(rest, tok));
+		m.params = params;
+		m.va_args_name = va_args_name;
+	} else {
+		add_macro(cpp, name, .Value_Like, copy_line(rest, tok));
+	}
+}
+
+
+join_tokens :: proc(tok, end: ^Token) -> string {
+	n := 1;
+	for t := tok; t != end && t.kind != .EOF; t = t.next {
+		if t != tok && t.has_space {
+			n += 1;
+		}
+		n += len(t.lit);
+	}
+
+	buf := make([]byte, n);
+
+	pos := 0;
+	for t := tok; t != end && t.kind != .EOF; t = t.next {
+		if t != tok && t.has_space {
+			buf[pos] = ' ';
+			pos += 1;
+		}
+		copy(buf[pos:], t.lit);
+		pos += len(t.lit);
+	}
+
+	return string(buf[:pos]);
+}
+
+read_include_filename :: proc(cpp: ^Preprocessor, rest: ^^Token, tok: ^Token) -> (filename: string, is_quote: bool) {
+	tok := tok;
+
+	if tok.kind == .String {
+		rest^ = skip_line(cpp, tok.next);
+		filename = tok.lit[1:len(tok.lit)-1];
+		is_quote = true;
+		return;
+	}
+
+	if tok.lit == "<" {
+		start := tok;
+		for ; tok.kind != .EOF; tok = tok.next {
+			if tok.at_bol || tok.kind == .EOF {
+				error(cpp, tok, "expected '>'");
+			}
+			is_quote = false;
+			if tok.lit == ">" {
+				break;
+			}
+		}
+		rest^ = skip_line(cpp, tok.next);
+		filename = join_tokens(start.next, tok);
+		return;
+	}
+
+	if tok.kind == .Ident {
+		tok2 := preprocess_internal(cpp, copy_line(rest, tok));
+		return read_include_filename(cpp, &tok2, tok2);
+	}
+
+	error(cpp, tok, "expected a filename");
+	return;
+}
+
+skip_cond_incl :: proc(tok: ^Token) -> ^Token {
+	next_skip :: proc(tok: ^Token) -> ^Token {
+		tok := tok;
+		for tok.kind != .EOF {
+			if is_hash(tok) {
+				switch tok.next.lit {
+				case "if", "ifdef", "ifndef":
+					tok = next_skip(tok.next.next);
+					continue;
+
+				case "endif":
+					return tok.next.next;
+				}
+			}
+			tok = tok.next;
+		}
+		return tok;
+	}
+
+	tok := tok;
+
+	loop: for tok.kind != .EOF {
+		if is_hash(tok) {
+			switch tok.next.lit {
+			case "if", "ifdef", "ifndef":
+				tok = next_skip(tok.next.next);
+				continue loop;
+
+			case "elif", "else", "endif":
+				break loop;
+			}
+		}
+
+		tok = tok.next;
+	}
+	return tok;
+}
+
+check_for_include_guard :: proc(tok: ^Token) -> (guard: string, ok: bool) {
+	if !is_hash(tok) || tok.next.lit != "ifndef" {
+		return;
+	}
+	tok := tok;
+	tok = tok.next.next;
+
+	if tok.kind != .Ident {
+		return;
+	}
+
+	m := tok.lit;
+	tok = tok.next;
+
+	if !is_hash(tok) || tok.next.lit != "define" || tok.next.lit != "macro" {
+		return;
+	}
+
+	for tok.kind != .EOF {
+		if !is_hash(tok) {
+			tok = tok.next;
+			continue;
+		}
+
+		if tok.next.lit == "endif" && tok.next.next.kind == .EOF {
+			return m, true;
+		}
+
+		switch tok.lit {
+		case "if", "ifdef", "ifndef":
+			tok = skip_cond_incl(tok.next);
+		case:
+			tok = tok.next;
+		}
+	}
+	return;
+}
+
+include_file :: proc(cpp: ^Preprocessor, tok: ^Token, path: string, filename_tok: ^Token) -> ^Token {
+	if cpp.pragma_once[path] {
+		return tok;
+	}
+
+	guard_name, guard_name_found := cpp.include_guards[path];
+	if guard_name_found && cpp.macros[guard_name] != nil {
+		return tok;
+	}
+
+	if !os.exists(path) {
+		error(cpp, filename_tok, "%s: cannot open file", path);
+		return tok;
+	}
+
+	cpp.include_level += 1;
+	if cpp.include_level > MAX_INCLUDE_LEVEL {
+		error(cpp, tok, "exceeded maximum nest amount: %d", MAX_INCLUDE_LEVEL);
+		return tok;
+	}
+
+	t := _init_tokenizer_from_preprocessor(&Tokenizer{}, cpp);
+	tok2 := tokenizer.tokenize_file(t, path, /*file.id*/1);
+	if tok2 == nil {
+		error(cpp, filename_tok, "%s: cannot open file", path);
+	}
+	cpp.include_level -= 1;
+
+	guard_name, guard_name_found = check_for_include_guard(tok2);
+	if guard_name_found {
+		cpp.include_guards[path] = guard_name;
+	}
+
+	return append_token(tok2, tok);
+}
+
+find_arg :: proc(args: ^Macro_Arg, tok: ^Token) -> ^Macro_Arg {
+	for ap := args; ap != nil; ap = ap.next {
+		if tok.lit == ap.name {
+			return ap;
+		}
+	}
+	return nil;
+}
+
+paste :: proc(cpp: ^Preprocessor, lhs, rhs: ^Token) -> ^Token {
+	buf := strings.concatenate({lhs.lit, rhs.lit});
+	t := _init_tokenizer_from_preprocessor(&Tokenizer{}, cpp);
+	tok := tokenizer.inline_tokenize(t, lhs, transmute([]byte)buf);
+	if tok.next.kind != .EOF {
+		error(cpp, lhs, "pasting forms '%s', an invalid token", buf);
+	}
+	return tok;
+}
+
+has_varargs :: proc(args: ^Macro_Arg) -> bool {
+	for ap := args; ap != nil; ap = ap.next {
+		if ap.name == "__VA_ARGS__" {
+			return ap.tok.kind != .EOF;
+		}
+	}
+	return false;
+}
+
+substitute_token :: proc(cpp: ^Preprocessor, tok: ^Token, args: ^Macro_Arg) -> ^Token {
+	head: Token;
+	curr := &head;
+	tok := tok;
+	for tok.kind != .EOF {
+		if tok.lit == "#" {
+			arg := find_arg(args, tok.next);
+			if arg == nil {
+				error(cpp, tok.next, "'#' is not followed by a macro parameter");
+			}
+			arg_tok := arg.tok if arg != nil else tok.next;
+			curr.next = stringize(cpp, tok, arg_tok);
+			curr = curr.next;
+			tok = tok.next.next;
+			continue;
+		}
+
+		if tok.lit == "," && tok.next.lit == "##" {
+			if arg := find_arg(args, tok.next.next); arg != nil && arg.is_va_args {
+				if arg.tok.kind == .EOF {
+					tok = tok.next.next.next;
+				} else {
+					curr.next = tokenizer.copy_token(tok);
+					curr = curr.next;
+					tok = tok.next.next;
+				}
+				continue;
+			}
+		}
+
+		if tok.lit == "##" {
+			if curr == &head {
+				error(cpp, tok, "'##' cannot appear at start of macro expansion");
+			}
+			if tok.next.kind == .EOF {
+				error(cpp, tok, "'##' cannot appear at end of macro expansion");
+			}
+
+			if arg := find_arg(args, tok.next); arg != nil {
+				if arg.tok.kind != .EOF {
+					curr^ = paste(cpp, curr, arg.tok)^;
+					for t := arg.tok.next; t.kind != .EOF; t = t.next {
+						curr.next = tokenizer.copy_token(t);
+						curr = curr.next;
+					}
+				}
+				tok = tok.next.next;
+				continue;
+			}
+
+			curr^ = paste(cpp, curr, tok.next)^;
+			tok = tok.next.next;
+			continue;
+		}
+
+		arg := find_arg(args, tok);
+
+		if arg != nil && tok.next.lit == "##" {
+			rhs := tok.next.next;
+
+			if arg.tok.kind == .EOF {
+				args2 := find_arg(args, rhs);
+				if args2 != nil {
+					for t := args.tok; t.kind != .EOF; t = t.next {
+						curr.next = tokenizer.copy_token(t);
+						curr = curr.next;
+					}
+				} else {
+					curr.next = tokenizer.copy_token(rhs);
+					curr = curr.next;
+				}
+				tok = rhs.next;
+				continue;
+			}
+
+			for t := arg.tok; t.kind != .EOF; t = t.next {
+				curr.next = tokenizer.copy_token(t);
+				curr = curr.next;
+			}
+			tok = tok.next;
+			continue;
+		}
+
+		if tok.lit == "__VA__OPT__" && tok.next.lit == "(" {
+			opt_arg := read_macro_arg_one(cpp, &tok, tok.next.next, true);
+			if has_varargs(args) {
+				for t := opt_arg.tok; t.kind != .EOF; t = t.next {
+					curr.next = t;
+					curr = curr.next;
+				}
+			}
+			tok = skip(cpp, tok, ")");
+			continue;
+		}
+
+		if arg != nil {
+			t := preprocess_internal(cpp, arg.tok);
+			t.at_bol = tok.at_bol;
+			t.has_space = tok.has_space;
+			for ; t.kind != .EOF; t = t.next {
+				curr.next = tokenizer.copy_token(t);
+				curr = curr.next;
+			}
+			tok = tok.next;
+			continue;
+		}
+
+		curr.next = tokenizer.copy_token(tok);
+		curr = curr.next;
+		tok = tok.next;
+		continue;
+	}
+
+	curr.next = tok;
+	return head.next;
+}
+
+read_macro_arg_one :: proc(cpp: ^Preprocessor, rest: ^^Token, tok: ^Token, read_rest: bool) -> ^Macro_Arg {
+	tok := tok;
+	head: Token;
+	curr := &head;
+	level := 0;
+	for {
+		if level == 0 && tok.lit == ")" {
+			break;
+		}
+		if level == 0 && !read_rest && tok.lit == "," {
+			break;
+		}
+
+		if tok.kind == .EOF {
+			error(cpp, tok, "premature end of input");
+		}
+
+		switch tok.lit {
+		case "(": level += 1;
+		case ")": level -= 1;
+		}
+
+		curr.next = tokenizer.copy_token(tok);
+		curr = curr.next;
+		tok = tok.next;
+	}
+	curr.next = tokenizer.new_eof(tok);
+
+	arg := new(Macro_Arg);
+	arg.tok = head.next;
+	rest^ = tok;
+	return arg;
+}
+
+read_macro_args :: proc(cpp: ^Preprocessor, rest: ^^Token, tok: ^Token, params: ^Macro_Param, va_args_name: string) -> ^Macro_Arg {
+	tok := tok;
+	start := tok;
+	tok = tok.next.next;
+
+	head: Macro_Arg;
+	curr := &head;
+
+	pp := params;
+	for ; pp != nil; pp = pp.next {
+		if curr != &head {
+			tok = skip(cpp, tok, ",");
+		}
+		curr.next = read_macro_arg_one(cpp, &tok, tok, false);
+		curr = curr.next;
+		curr.name = pp.name;
+	}
+
+	if va_args_name != "" {
+		arg: ^Macro_Arg;
+		if tok.lit == ")" {
+			arg = new(Macro_Arg);
+			arg.tok = tokenizer.new_eof(tok);
+		} else {
+			if pp != params {
+				tok = skip(cpp, tok, ",");
+			}
+			arg = read_macro_arg_one(cpp, &tok, tok, true);
+		}
+		arg.name = va_args_name;
+		arg.is_va_args = true;
+		curr.next = arg;
+		curr = curr.next;
+	} else if pp != nil {
+		error(cpp, start, "too many arguments");
+	}
+
+	skip(cpp, tok, ")");
+	rest^ = tok;
+	return head.next;
+}
+
+expand_macro :: proc(cpp: ^Preprocessor, rest: ^^Token, tok: ^Token) -> bool {
+	if tokenizer.hide_set_contains(tok.hide_set, tok.lit) {
+		return false;
+	}
+	tok := tok;
+	m := find_macro(cpp, tok);
+	if m == nil {
+		return false;
+	}
+
+	if m.handler != nil {
+		rest^ = m.handler(cpp, tok);
+		rest^.next = tok.next;
+		return true;
+	}
+
+	if m.kind == .Value_Like {
+		hs := tokenizer.hide_set_union(tok.hide_set, tokenizer.new_hide_set(m.name));
+		body := tokenizer.add_hide_set(m.body, hs);
+		for t := body; t.kind != .EOF; t = t.next {
+			t.origin = tok;
+		}
+		rest^ = append_token(body, tok.next);
+		rest^.at_bol = tok.at_bol;
+		rest^.has_space = tok.has_space;
+		return true;
+	}
+
+	if tok.next.lit != "(" {
+		return false;
+	}
+
+	macro_token := tok;
+	args := read_macro_args(cpp, &tok, tok, m.params, m.va_args_name);
+	close_paren := tok;
+
+	hs := tokenizer.hide_set_intersection(macro_token.hide_set, close_paren.hide_set);
+	hs = tokenizer.hide_set_union(hs, tokenizer.new_hide_set(m.name));
+
+	body := substitute_token(cpp, m.body, args);
+	body = tokenizer.add_hide_set(body, hs);
+	for t := body; t.kind != .EOF; t = t.next {
+		t.origin = macro_token;
+	}
+	rest^ = append_token(body, tok.next);
+	rest^.at_bol = macro_token.at_bol;
+	rest^.has_space = macro_token.has_space;
+	return true;
+}
+
+search_include_next :: proc(cpp: ^Preprocessor, filename: string) -> (path: string, ok: bool) {
+	for ; cpp.include_next_index < len(cpp.include_paths); cpp.include_next_index += 1 {
+		tpath := filepath.join(elems={cpp.include_paths[cpp.include_next_index], filename}, allocator=context.temp_allocator);
+		if os.exists(tpath) {
+			return strings.clone(tpath), true;
+		}
+	}
+	return;
+}
+
+search_include_paths :: proc(cpp: ^Preprocessor, filename: string) -> (path: string, ok: bool) {
+	if filepath.is_abs(filename) {
+		return filename, true;
+	}
+
+	if path, ok = cpp.filepath_cache[filename]; ok {
+		return;
+	}
+
+	for include_path in cpp.include_paths {
+		tpath := filepath.join(elems={include_path, filename}, allocator=context.temp_allocator);
+		if os.exists(tpath) {
+			path, ok = strings.clone(tpath), true;
+			cpp.filepath_cache[filename] = path;
+			return;
+		}
+	}
+
+	return;
+}
+
+read_const_expr :: proc(cpp: ^Preprocessor, rest: ^^Token, tok: ^Token) -> ^Token {
+	tok := tok;
+	tok = copy_line(rest, tok);
+	head: Token;
+	curr := &head;
+	for tok.kind != .EOF {
+		if tok.lit == "defined" {
+			start := tok;
+			has_paren := consume(&tok, tok.next, "(");
+			if tok.kind != .Ident {
+				error(cpp, start, "macro name must be an identifier");
+			}
+			m := find_macro(cpp, tok);
+			tok = tok.next;
+
+			if has_paren {
+				tok = skip(cpp, tok, ")");
+			}
+
+			curr.next = new_number_token(cpp, 1 if m != nil else 0, start);
+			curr = curr.next;
+			continue;
+		}
+
+		curr.next = tok;
+		curr = curr.next;
+		tok = tok.next;
+	}
+
+	curr.next = tok;
+	return head.next;
+}
+
+eval_const_expr :: proc(cpp: ^Preprocessor, rest: ^^Token, tok: ^Token) -> (val: i64) {
+	tok := tok;
+	start := tok;
+	expr := read_const_expr(cpp, rest, tok.next);
+	expr = preprocess_internal(cpp, expr);
+
+	if expr.kind == .EOF {
+		error(cpp, start, "no expression");
+	}
+
+	for t := expr; t.kind != .EOF; t = t.next {
+		if t.kind == .Ident {
+			next := t.next;
+			t^ = new_number_token(cpp, 0, t)^;
+			t.next = next;
+		}
+	}
+
+	val = 1;
+	convert_pp_tokens(cpp, expr, tokenizer.default_is_keyword);
+
+	rest2: ^Token;
+	val = const_expr(&rest2, expr);
+	if rest2 != nil && rest2.kind != .EOF {
+		error(cpp, rest2, "extra token");
+	}
+	return;
+}
+
+push_cond_incl :: proc(cpp: ^Preprocessor, tok: ^Token, included: bool) -> ^Cond_Incl {
+	ci := new(Cond_Incl);
+	ci.next = cpp.cond_incl;
+	ci.state = .In_Then;
+	ci.tok = tok;
+	ci.included = included;
+	cpp.cond_incl = ci;
+	return ci;
+}
+
+read_line_marker:: proc(cpp: ^Preprocessor, rest: ^^Token, tok: ^Token) {
+	tok := tok;
+	start := tok;
+	tok = preprocess(cpp, copy_line(rest, tok));
+	if tok.kind != .Number {
+		error(cpp, tok, "invalid line marker");
+	}
+	ival, _ := tok.val.(i64);
+	start.file.line_delta = int(ival - i64(start.pos.line));
+	tok = tok.next;
+	if tok.kind == .EOF {
+		return;
+	}
+
+	if tok.kind != .String {
+		error(cpp, tok, "filename expected");
+	}
+	start.file.display_name = tok.lit;
+}
+
+preprocess_internal :: proc(cpp: ^Preprocessor, tok: ^Token) -> ^Token {
+	head: Token;
+	curr := &head;
+
+	tok := tok;
+	for tok != nil && tok.kind != .EOF {
+		if expand_macro(cpp, &tok, tok) {
+			continue;
+		}
+
+		if !is_hash(tok) {
+			if tok.file != nil {
+				tok.line_delta = tok.file.line_delta;
+			}
+			curr.next = tok;
+			curr = curr.next;
+			tok = tok.next;
+			continue;
+		}
+
+		start := tok;
+		tok = tok.next;
+
+		switch tok.lit {
+		case "include":
+			filename, is_quote := read_include_filename(cpp, &tok, tok.next);
+			is_absolute := filepath.is_abs(filename);
+			if is_absolute {
+				tok = include_file(cpp, tok, filename, start.next.next);
+				continue;
+			}
+
+			if is_quote {
+				dir := "";
+				if start.file != nil {
+					dir = filepath.dir(start.file.name);
+				}
+				path := filepath.join(dir, filename);
+				if os.exists(path) {
+					tok = include_file(cpp, tok, path, start.next.next);
+					continue;
+				}
+			}
+
+			path, ok := search_include_paths(cpp, filename);
+			if !ok {
+				path = filename;
+			}
+			tok = include_file(cpp, tok, path, start.next.next);
+			continue;
+
+		case "include_next":
+			filename, _ := read_include_filename(cpp, &tok, tok.next);
+			path, ok := search_include_next(cpp, filename);
+			if !ok {
+				path = filename;
+			}
+			tok = include_file(cpp, tok, path, start.next.next);
+			continue;
+
+		case "define":
+			read_macro_definition(cpp, &tok, tok.next);
+			continue;
+
+		case "undef":
+			tok = tok.next;
+			if tok.kind != .Ident {
+				error(cpp, tok, "macro name must be an identifier");
+			}
+			undef_macro(cpp, tok.lit);
+			tok = skip_line(cpp, tok.next);
+			continue;
+
+		case "if":
+			val := eval_const_expr(cpp, &tok, tok);
+			push_cond_incl(cpp, start, val != 0);
+			if val == 0 {
+				tok = skip_cond_incl(tok);
+			}
+			continue;
+
+		case "ifdef":
+			defined := find_macro(cpp, tok.next);
+			push_cond_incl(cpp, tok, defined != nil);
+			tok = skip_line(cpp, tok.next.next);
+			if defined == nil {
+				tok = skip_cond_incl(tok);
+			}
+			continue;
+
+		case "ifndef":
+			defined := find_macro(cpp, tok.next);
+			push_cond_incl(cpp, tok, defined != nil);
+			tok = skip_line(cpp, tok.next.next);
+			if !(defined == nil) {
+				tok = skip_cond_incl(tok);
+			}
+			continue;
+
+		case "elif":
+			if cpp.cond_incl == nil || cpp.cond_incl.state == .In_Else {
+				error(cpp, start, "stray #elif");
+			}
+			if cpp.cond_incl != nil {
+				cpp.cond_incl.state = .In_Elif;
+			}
+
+			if (cpp.cond_incl != nil && !cpp.cond_incl.included) && eval_const_expr(cpp, &tok, tok) != 0 {
+				cpp.cond_incl.included = true;
+			} else {
+				tok = skip_cond_incl(tok);
+			}
+			continue;
+
+		case "else":
+			if cpp.cond_incl == nil || cpp.cond_incl.state == .In_Else {
+				error(cpp, start, "stray #else");
+			}
+			if cpp.cond_incl != nil {
+				cpp.cond_incl.state = .In_Else;
+			}
+			tok = skip_line(cpp, tok.next);
+
+			if cpp.cond_incl != nil {
+				tok = skip_cond_incl(tok);
+			}
+			continue;
+
+		case "endif":
+			if cpp.cond_incl == nil {
+				error(cpp, start, "stray #endif");
+			} else {
+				cpp.cond_incl = cpp.cond_incl.next;
+			}
+			tok = skip_line(cpp, tok.next);
+			continue;
+
+		case "line":
+			read_line_marker(cpp, &tok, tok.next);
+			continue;
+
+		case "pragma":
+			if tok.next.lit == "once" {
+				cpp.pragma_once[tok.pos.file] = true;
+				tok = skip_line(cpp, tok.next.next);
+				continue;
+			}
+
+			pragma_tok, pragma_end := tok, tok;
+
+			for tok != nil && tok.kind != .EOF {
+				pragma_end = tok;
+				tok = tok.next;
+				if tok.at_bol {
+					break;
+				}
+			}
+			pragma_end.next = tokenizer.new_eof(tok);
+			if cpp.pragma_handler != nil {
+				cpp.pragma_handler(cpp, pragma_tok.next);
+				continue;
+			}
+
+			continue;
+
+		case "error":
+			error(cpp, tok, "error");
+		}
+
+		if tok.kind == .PP_Number {
+			read_line_marker(cpp, &tok, tok);
+			continue;
+		}
+
+		if !tok.at_bol {
+			error(cpp, tok, "invalid preprocessor directive");
+		}
+	}
+
+	curr.next = tok;
+	return head.next;
+}
+
+
+preprocess :: proc(cpp: ^Preprocessor, tok: ^Token) -> ^Token {
+	tok := tok;
+	tok = preprocess_internal(cpp, tok);
+	if cpp.cond_incl != nil {
+		error(cpp, tok, "unterminated conditional directive");
+	}
+	convert_pp_tokens(cpp, tok, tokenizer.default_is_keyword);
+	join_adjacent_string_literals(cpp, tok);
+	for t := tok; t != nil; t = t.next {
+		t.pos.line += t.line_delta;
+	}
+	return tok;
+}
+
+
+define_macro :: proc(cpp: ^Preprocessor, name, def: string) {
+	src := transmute([]byte)def;
+
+	file := new(tokenizer.File);
+	file.id = -1;
+	file.src = src;
+	file.name = "<built-in>";
+	file.display_name = file.name;
+
+
+	t := _init_tokenizer_from_preprocessor(&Tokenizer{}, cpp);
+	tok := tokenizer.tokenize(t, file);
+	add_macro(cpp, name, .Value_Like, tok);
+}
+
+
+file_macro :: proc(cpp: ^Preprocessor, tok: ^Token) -> ^Token {
+	tok := tok;
+	for tok.origin != nil {
+		tok = tok.origin;
+	}
+	i := i64(tok.pos.line + tok.file.line_delta);
+	return new_number_token(cpp, i, tok);
+}
+line_macro :: proc(cpp: ^Preprocessor, tok: ^Token) -> ^Token {
+	tok := tok;
+	for tok.origin != nil {
+		tok = tok.origin;
+	}
+	return new_string_token(cpp, tok.file.display_name, tok);
+}
+counter_macro :: proc(cpp: ^Preprocessor, tok: ^Token) -> ^Token {
+	i := cpp.counter;
+	cpp.counter += 1;
+	return new_number_token(cpp, i, tok);
+}
+
+init_default_macros :: proc(cpp: ^Preprocessor) {
+	define_macro(cpp, "__C99_MACRO_WITH_VA_ARGS", "1");
+	define_macro(cpp, "__alignof__", "_Alignof");
+	define_macro(cpp, "__const__", "const");
+	define_macro(cpp, "__inline__", "inline");
+	define_macro(cpp, "__signed__", "signed");
+	define_macro(cpp, "__typeof__", "typeof");
+	define_macro(cpp, "__volatile__", "volatile");
+
+	add_builtin(cpp, "__FILE__", file_macro);
+	add_builtin(cpp, "__LINE__", line_macro);
+	add_builtin(cpp, "__COUNTER__", counter_macro);
+}
+
+init_lookup_tables :: proc(cpp: ^Preprocessor, allocator := context.allocator) {
+	context.allocator = allocator;
+	reserve(&cpp.macros,         max(16, cap(cpp.macros)));
+	reserve(&cpp.pragma_once,    max(16, cap(cpp.pragma_once)));
+	reserve(&cpp.include_guards, max(16, cap(cpp.include_guards)));
+	reserve(&cpp.filepath_cache, max(16, cap(cpp.filepath_cache)));
+}
diff --git a/core/c/frontend/preprocessor/unquote.odin b/core/c/frontend/preprocessor/unquote.odin
new file mode 100644
index 000000000..4aa4926e7
--- /dev/null
+++ b/core/c/frontend/preprocessor/unquote.odin
@@ -0,0 +1,154 @@
+package c_frontend_preprocess
+
+import "core:unicode/utf8"
+
+unquote_char :: proc(str: string, quote: byte) -> (r: rune, multiple_bytes: bool, tail_string: string, success: bool) {
+	hex_to_int :: proc(c: byte) -> int {
+		switch c {
+		case '0'..'9': return int(c-'0');
+		case 'a'..'f': return int(c-'a')+10;
+		case 'A'..'F': return int(c-'A')+10;
+		}
+		return -1;
+	}
+	w: int;
+
+	if str[0] == quote && quote == '"' {
+		return;
+	} else if str[0] >= 0x80 {
+		r, w = utf8.decode_rune_in_string(str);
+		return r, true, str[w:], true;
+	} else if str[0] != '\\' {
+		return rune(str[0]), false, str[1:], true;
+	}
+
+	if len(str) <= 1 {
+		return;
+	}
+	s := str;
+	c := s[1];
+	s = s[2:];
+
+	switch c {
+	case: r = rune(c);
+
+	case 'a':  r = '\a';
+	case 'b':  r = '\b';
+	case 'e':  r = '\e';
+	case 'f':  r = '\f';
+	case 'n':  r = '\n';
+	case 'r':  r = '\r';
+	case 't':  r = '\t';
+	case 'v':  r = '\v';
+	case '\\': r = '\\';
+
+	case '"':  r = '"';
+	case '\'': r = '\'';
+
+	case '0'..'7':
+		v := int(c-'0');
+		if len(s) < 2 {
+			return;
+		}
+		for i in 0..<len(s) {
+			d := int(s[i]-'0');
+			if d < 0 || d > 7 {
+				return;
+			}
+			v = (v<<3) | d;
+		}
+		s = s[2:];
+		if v > 0xff {
+			return;
+		}
+		r = rune(v);
+
+	case 'x', 'u', 'U':
+		count: int;
+		switch c {
+		case 'x': count = 2;
+		case 'u': count = 4;
+		case 'U': count = 8;
+		}
+
+		if len(s) < count {
+			return;
+		}
+
+		for i in 0..<count {
+			d := hex_to_int(s[i]);
+			if d < 0 {
+				return;
+			}
+			r = (r<<4) | rune(d);
+		}
+		s = s[count:];
+		if c == 'x' {
+			break;
+		}
+		if r > utf8.MAX_RUNE {
+			return;
+		}
+		multiple_bytes = true;
+	}
+
+	success = true;
+	tail_string = s;
+	return;
+}
+
+unquote_string :: proc(lit: string, allocator := context.allocator) -> (res: string, allocated, success: bool) {
+	contains_rune :: proc(s: string, r: rune) -> int {
+		for c, offset in s {
+			if c == r {
+				return offset;
+			}
+		}
+		return -1;
+	}
+
+	assert(len(lit) >= 2);
+
+	s := lit;
+	quote := '"';
+
+	if s == `""` {
+		return "", false, true;
+	}
+
+	if contains_rune(s, '\n') >= 0 {
+		return s, false, false;
+	}
+
+	if contains_rune(s, '\\') < 0 && contains_rune(s, quote) < 0 {
+		if quote == '"' {
+			return s, false, true;
+		}
+	}
+	s = s[1:len(s)-1];
+
+
+	buf_len := 3*len(s) / 2;
+	buf := make([]byte, buf_len, allocator);
+	offset := 0;
+	for len(s) > 0 {
+		r, multiple_bytes, tail_string, ok := unquote_char(s, byte(quote));
+		if !ok {
+			delete(buf);
+			return s, false, false;
+		}
+		s = tail_string;
+		if r < 0x80 || !multiple_bytes {
+			buf[offset] = byte(r);
+			offset += 1;
+		} else {
+			b, w := utf8.encode_rune(r);
+			copy(buf[offset:], b[:w]);
+			offset += w;
+		}
+	}
+
+	new_string := string(buf[:offset]);
+
+	return new_string, true, true;
+}
diff --git a/core/c/frontend/tokenizer/doc.odin b/core/c/frontend/tokenizer/doc.odin
new file mode 100644
index 000000000..bfac6e6fa
--- /dev/null
+++ b/core/c/frontend/tokenizer/doc.odin
@@ -0,0 +1,35 @@
+/*
+package demo
+
+import tokenizer "core:c/frontend/tokenizer"
+import preprocessor "core:c/frontend/preprocessor"
+import "core:fmt"
+import "core:path/filepath"
+
+main :: proc() {
+	t := &tokenizer.Tokenizer{};
+	tokenizer.init_defaults(t);
+
+	cpp := &preprocessor.Preprocessor{};
+	cpp.warn, cpp.err = t.warn, t.err;
+	preprocessor.init_lookup_tables(cpp);
+	preprocessor.init_default_macros(cpp);
+	cpp.include_paths = {"W:/Odin/core/c/frontend/include"};
+
+	tok := tokenizer.tokenize_file(t, match_path, 1);
+
+	tok = preprocessor.preprocess(cpp, tok);
+	if tok != nil {
+		for t := tok; t.kind != .EOF; t = t.next {
+			fmt.println(t.lit);
+		}
+	}
+
+	fmt.println("[Done]");
+}
+*/
+
+
+package c_frontend_tokenizer
+
+
diff --git a/core/c/frontend/tokenizer/hide_set.odin b/core/c/frontend/tokenizer/hide_set.odin
new file mode 100644
index 000000000..9cf3b4aea
--- /dev/null
+++ b/core/c/frontend/tokenizer/hide_set.odin
@@ -0,0 +1,68 @@
+package c_frontend_tokenizer
+
+// NOTE(bill): This is a really dumb approach for a hide set,
+// but it's really simple and probably fast enough in practice
+
+
+Hide_Set :: struct {
+	next: ^Hide_Set,
+	name: string,
+}
+
+
+new_hide_set :: proc(name: string) -> ^Hide_Set {
+	hs := new(Hide_Set);
+	hs.name = name;
+	return hs;
+}
+
+hide_set_contains :: proc(hs: ^Hide_Set, name: string) -> bool {
+	for h := hs; h != nil; h = h.next {
+		if h.name == name {
+			return true;
+		}
+	}
+	return false;
+}
+
+
+hide_set_union :: proc(a, b: ^Hide_Set) -> ^Hide_Set {
+	head: Hide_Set;
+	curr := &head;
+
+	for h := a; h != nil; h = h.next {
+		curr.next = new_hide_set(h.name);
+		curr = curr.next;
+	}
+	curr.next = b;
+	return head.next;
+}
+
+
+hide_set_intersection :: proc(a, b: ^Hide_Set) -> ^Hide_Set {
+	head: Hide_Set;
+	curr := &head;
+
+	for h := a; h != nil; h = h.next {
+		if hide_set_contains(b, h.name) {
+			curr.next = new_hide_set(h.name);
+			curr = curr.next;
+		}
+	}
+	return head.next;
+}
+
+
+add_hide_set :: proc(tok: ^Token, hs: ^Hide_Set) -> ^Token {
+	head: Token;
+	curr := &head;
+
+	tok := tok;
+	for ; tok != nil; tok = tok.next {
+		t := copy_token(tok);
+		t.hide_set = hide_set_union(t.hide_set, hs);
+		curr.next = t;
+		curr = curr.next;
+	}
+	return head.next;
+}
diff --git a/core/c/frontend/tokenizer/token.odin b/core/c/frontend/tokenizer/token.odin
new file mode 100644
index 000000000..a85468e6a
--- /dev/null
+++ b/core/c/frontend/tokenizer/token.odin
@@ -0,0 +1,169 @@
+package c_frontend_tokenizer
+
+
+Pos :: struct {
+	file:   string,
+	line:   int,
+	column: int,
+	offset: int,
+}
+
+Token_Kind :: enum {
+	Invalid,
+	Ident,
+	Punct,
+	Keyword,
+	Char,
+	String,
+	Number,
+	PP_Number,
+	Comment,
+	EOF,
+}
+
+File :: struct {
+	name: string,
+	id:   int,
+	src:  []byte,
+
+	display_name: string,
+	line_delta:   int,
+}
+
+
+Token_Type_Hint :: enum u8 {
+	None,
+
+	Int,
+	Long,
+	Long_Long,
+
+	Unsigned_Int,
+	Unsigned_Long,
+	Unsigned_Long_Long,
+
+	Float,
+	Double,
+	Long_Double,
+
+	UTF_8,
+	UTF_16,
+	UTF_32,
+	UTF_Wide,
+}
+
+Token_Value :: union {
+	i64,
+	f64,
+	string,
+	[]u16,
+	[]u32,
+}
+
+Token :: struct {
+	kind: Token_Kind,
+	next: ^Token,
+	lit: string,
+
+	pos:   Pos,
+	file:  ^File,
+	line_delta: int,
+	at_bol:     bool,
+	has_space:  bool,
+
+	type_hint: Token_Type_Hint,
+	val: Token_Value,
+	prefix: string,
+
+	// Preprocessor values
+	hide_set: ^Hide_Set,
+	origin:   ^Token,
+}
+
+Is_Keyword_Proc :: #type proc(tok: ^Token) -> bool;
+
+copy_token :: proc(tok: ^Token) -> ^Token {
+	t := new_clone(tok^);
+	t.next = nil;
+	return t;
+}
+
+new_eof :: proc(tok: ^Token) -> ^Token {
+	t := new_clone(tok^);
+	t.kind = .EOF;
+	t.lit = "";
+	return t;
+}
+
+default_is_keyword :: proc(tok: ^Token) -> bool {
+	if tok.kind == .Keyword {
+		return true;
+	}
+	if len(tok.lit) > 0 {
+		return default_keyword_set[tok.lit];
+	}
+	return false;
+}
+
+
+token_name := [Token_Kind]string {
+	.Invalid   = "invalid",
+	.Ident     = "ident",
+	.Punct     = "punct",
+	.Keyword   = "keyword",
+	.Char      = "char",
+	.String    = "string",
+	.Number    = "number",
+	.PP_Number = "preprocessor number",
+	.Comment   = "comment",
+	.EOF       = "eof",
+};
+
+default_keyword_set := map[string]bool{
+	"auto"          = true,
+	"break"         = true,
+	"case"          = true,
+	"char"          = true,
+	"const"         = true,
+	"continue"      = true,
+	"default"       = true,
+	"do"            = true,
+	"double"        = true,
+	"else"          = true,
+	"enum"          = true,
+	"extern"        = true,
+	"float"         = true,
+	"for"           = true,
+	"goto"          = true,
+	"if"            = true,
+	"int"           = true,
+	"long"          = true,
+	"register"      = true,
+	"restrict"      = true,
+	"return"        = true,
+	"short"         = true,
+	"signed"        = true,
+	"sizeof"        = true,
+	"static"        = true,
+	"struct"        = true,
+	"switch"        = true,
+	"typedef"       = true,
+	"union"         = true,
+	"unsigned"      = true,
+	"void"          = true,
+	"volatile"      = true,
+	"while"         = true,
+	"_Alignas"      = true,
+	"_Alignof"      = true,
+	"_Atomic"       = true,
+	"_Bool"         = true,
+	"_Generic"      = true,
+	"_Noreturn"     = true,
+	"_Thread_local" = true,
+	"__restrict"    = true,
+	"typeof"        = true,
+	"asm"           = true,
+	"__restrict__"  = true,
+	"__thread"      = true,
+	"__attribute__" = true,
+};
diff --git a/core/c/frontend/tokenizer/tokenizer.odin b/core/c/frontend/tokenizer/tokenizer.odin
new file mode 100644
index 000000000..d65a8cd4e
--- /dev/null
+++ b/core/c/frontend/tokenizer/tokenizer.odin
@@ -0,0 +1,667 @@
+package c_frontend_tokenizer
+
+import "core:fmt"
+import "core:os"
+import "core:strings"
+import "core:unicode/utf8"
+
+
+Error_Handler :: #type proc(pos: Pos, fmt: string, args: ..any);
+
+
+Tokenizer :: struct {
+	// Immutable data
+	path: string,
+	src:  []byte,
+
+
+	// Tokenizing state
+	ch:          rune,
+	offset:      int,
+	read_offset: int,
+	line_offset: int,
+	line_count:  int,
+
+	// Extra information for tokens
+	at_bol:    bool,
+	has_space: bool,
+
+	// Mutable data
+	err:  Error_Handler,
+	warn: Error_Handler,
+	error_count:   int,
+	warning_count: int,
+}
+
+init_defaults :: proc(t: ^Tokenizer, err: Error_Handler = default_error_handler, warn: Error_Handler = default_warn_handler) {
+	t.err = err;
+	t.warn = warn;
+}
+
+
+@(private)
+offset_to_pos :: proc(t: ^Tokenizer, offset: int) -> (pos: Pos) {
+	pos.file = t.path;
+	pos.offset = offset;
+	pos.line = t.line_count;
+	pos.column = offset - t.line_offset + 1;
+	return;
+}
+
+default_error_handler :: proc(pos: Pos, msg: string, args: ..any) {
+	fmt.eprintf("%s(%d:%d) ", pos.file, pos.line, pos.column);
+	fmt.eprintf(msg, ..args);
+	fmt.eprintf("\n");
+}
+
+default_warn_handler :: proc(pos: Pos, msg: string, args: ..any) {
+	fmt.eprintf("%s(%d:%d) warning: ", pos.file, pos.line, pos.column);
+	fmt.eprintf(msg, ..args);
+	fmt.eprintf("\n");
+}
+
+error_offset :: proc(t: ^Tokenizer, offset: int, msg: string, args: ..any) {
+	pos := offset_to_pos(t, offset);
+	if t.err != nil {
+		t.err(pos, msg, ..args);
+	}
+	t.error_count += 1;
+}
+
+warn_offset :: proc(t: ^Tokenizer, offset: int, msg: string, args: ..any) {
+	pos := offset_to_pos(t, offset);
+	if t.warn != nil {
+		t.warn(pos, msg, ..args);
+	}
+	t.warning_count += 1;
+}
+
+error :: proc(t: ^Tokenizer, tok: ^Token, msg: string, args: ..any) {
+	pos := tok.pos;
+	if t.err != nil {
+		t.err(pos, msg, ..args);
+	}
+	t.error_count += 1;
+}
+
+warn :: proc(t: ^Tokenizer, tok: ^Token, msg: string, args: ..any) {
+	pos := tok.pos;
+	if t.warn != nil {
+		t.warn(pos, msg, ..args);
+	}
+	t.warning_count += 1;
+}
+
+
+advance_rune :: proc(t: ^Tokenizer) {
+	if t.read_offset < len(t.src) {
+		t.offset = t.read_offset;
+		if t.ch == '\n' {
+			t.at_bol = true;
+			t.line_offset = t.offset;
+			t.line_count += 1;
+		}
+		r, w := rune(t.src[t.read_offset]), 1;
+		switch {
+		case r == 0:
+			error_offset(t, t.offset, "illegal character NUL");
+		case r >= utf8.RUNE_SELF:
+			r, w = utf8.decode_rune(t.src[t.read_offset:]);
+			if r == utf8.RUNE_ERROR && w == 1 {
+				error_offset(t, t.offset, "illegal UTF-8 encoding");
+			} else if r == utf8.RUNE_BOM && t.offset > 0 {
+				error_offset(t, t.offset, "illegal byte order mark");
+			}
+		}
+		t.read_offset += w;
+		t.ch = r;
+	} else {
+		t.offset = len(t.src);
+		if t.ch == '\n' {
+			t.at_bol = true;
+			t.line_offset = t.offset;
+			t.line_count += 1;
+		}
+		t.ch = -1;
+	}
+}
+
+advance_rune_n :: proc(t: ^Tokenizer, n: int) {
+	for in 0..<n {
+		advance_rune(t);
+	}
+}
+
+is_digit :: proc(r: rune) -> bool {
+	return '0' <= r && r <= '9';
+}
+
+skip_whitespace :: proc(t: ^Tokenizer) {
+	for {
+		switch t.ch {
+		case ' ', '\t', '\r', '\v', '\f', '\n':
+			t.has_space = true;
+			advance_rune(t);
+		case:
+			return;
+		}
+	}
+}
+
+scan_comment :: proc(t: ^Tokenizer) -> string {
+	offset := t.offset-1;
+	next := -1;
+	general: {
+		if t.ch == '/'{ // line comments
+			advance_rune(t);
+			for t.ch != '\n' && t.ch >= 0 {
+				advance_rune(t);
+			}
+
+			next = t.offset;
+			if t.ch == '\n' {
+				next += 1;
+			}
+			break general;
+		}
+
+		/* style comment */
+		advance_rune(t);
+		for t.ch >= 0 {
+			ch := t.ch;
+			advance_rune(t);
+			if ch == '*' && t.ch == '/' {
+				advance_rune(t);
+				next = t.offset;
+				break general;
+			}
+		}
+
+		error_offset(t, offset, "comment not terminated");
+	}
+
+	lit := t.src[offset : t.offset];
+
+	// NOTE(bill): Strip CR for line comments
+	for len(lit) > 2 && lit[1] == '/' && lit[len(lit)-1] == '\r' {
+		lit = lit[:len(lit)-1];
+	}
+
+
+	return string(lit);
+}
+
+scan_identifier :: proc(t: ^Tokenizer) -> string {
+	offset := t.offset;
+
+	for is_ident1(t.ch) {
+		advance_rune(t);
+	}
+
+	return string(t.src[offset : t.offset]);
+}
+
+scan_string :: proc(t: ^Tokenizer) -> string {
+	offset := t.offset-1;
+
+	for {
+		ch := t.ch;
+		if ch == '\n' || ch < 0 {
+			error_offset(t, offset, "string literal was not terminated");
+			break;
+		}
+		advance_rune(t);
+		if ch == '"' {
+			break;
+		}
+		if ch == '\\' {
+			scan_escape(t);
+		}
+	}
+
+	return string(t.src[offset : t.offset]);
+}
+
+digit_val :: proc(r: rune) -> int {
+	switch r {
+	case '0'..'9':
+		return int(r-'0');
+	case 'A'..'F':
+		return int(r-'A' + 10);
+	case 'a'..'f':
+		return int(r-'a' + 10);
+	}
+	return 16;
+}
+
+scan_escape :: proc(t: ^Tokenizer) -> bool {
+	offset := t.offset;
+
+	esc := t.ch;
+	n: int;
+	base, max: u32;
+	switch esc {
+	case 'a', 'b', 'e', 'f', 'n', 't', 'v', 'r', '\\', '\'', '\"':
+		advance_rune(t);
+		return true;
+
+	case '0'..'7':
+		for digit_val(t.ch) < 8 {
+			advance_rune(t);
+		}
+		return true;
+	case 'x':
+		advance_rune(t);
+		for digit_val(t.ch) < 16 {
+			advance_rune(t);
+		}
+		return true;
+	case 'u':
+		advance_rune(t);
+		n, base, max = 4, 16, utf8.MAX_RUNE;
+	case 'U':
+		advance_rune(t);
+		n, base, max = 8, 16, utf8.MAX_RUNE;
+	case:
+		if t.ch < 0 {
+			error_offset(t, offset, "escape sequence was not terminated");
+		} else {
+			break;
+		}
+		return false;
+	}
+
+	x: u32;
+	main_loop: for n > 0 {
+		d := u32(digit_val(t.ch));
+		if d >= base {
+			if t.ch == '"' || t.ch == '\'' {
+				break main_loop;
+			}
+			if t.ch < 0 {
+				error_offset(t, t.offset, "escape sequence was not terminated");
+			} else {
+				error_offset(t, t.offset, "illegal character '%r' : %d in escape sequence", t.ch, t.ch);
+			}
+			return false;
+		}
+
+		x = x*base + d;
+		advance_rune(t);
+		n -= 1;
+	}
+
+	if x > max || 0xd800 <= x && x <= 0xe000 {
+		error_offset(t, offset, "escape sequence is an invalid Unicode code point");
+		return false;
+	}
+	return true;
+}
+
+scan_rune :: proc(t: ^Tokenizer) -> string {
+	offset := t.offset-1;
+	valid := true;
+	n := 0;
+	for {
+		ch := t.ch;
+		if ch == '\n' || ch < 0 {
+			if valid {
+				error_offset(t, offset, "rune literal not terminated");
+				valid = false;
+			}
+			break;
+		}
+		advance_rune(t);
+		if ch == '\'' {
+			break;
+		}
+		n += 1;
+		if ch == '\\' {
+			if !scan_escape(t)  {
+				valid = false;
+			}
+		}
+	}
+
+	if valid && n != 1 {
+		error_offset(t, offset, "illegal rune literal");
+	}
+
+	return string(t.src[offset : t.offset]);
+}
+
+scan_number :: proc(t: ^Tokenizer, seen_decimal_point: bool) -> (Token_Kind, string) {
+	scan_mantissa :: proc(t: ^Tokenizer, base: int) {
+		for digit_val(t.ch) < base {
+			advance_rune(t);
+		}
+	}
+	scan_exponent :: proc(t: ^Tokenizer) {
+		if t.ch == 'e' || t.ch == 'E' || t.ch == 'p' || t.ch == 'P' {
+			advance_rune(t);
+			if t.ch == '-' || t.ch == '+' {
+				advance_rune(t);
+			}
+			if digit_val(t.ch) < 10 {
+				scan_mantissa(t, 10);
+			} else {
+				error_offset(t, t.offset, "illegal floating-point exponent");
+			}
+		}
+	}
+	scan_fraction :: proc(t: ^Tokenizer) -> (early_exit: bool) {
+		if t.ch == '.' && peek(t) == '.' {
+			return true;
+		}
+		if t.ch == '.' {
+			advance_rune(t);
+			scan_mantissa(t, 10);
+		}
+		return false;
+	}
+
+	check_end := true;
+
+
+	offset := t.offset;
+	seen_point := seen_decimal_point;
+
+	if seen_point {
+		offset -= 1;
+		scan_mantissa(t, 10);
+		scan_exponent(t);
+	} else {
+		if t.ch == '0' {
+			int_base :: inline proc(t: ^Tokenizer, base: int, msg: string) {
+				prev := t.offset;
+				advance_rune(t);
+				scan_mantissa(t, base);
+				if t.offset - prev <= 1 {
+					error_offset(t, t.offset, msg);
+				}
+			}
+
+			advance_rune(t);
+			switch t.ch {
+			case 'b', 'B':
+				int_base(t, 2, "illegal binary integer");
+			case 'x', 'X':
+				int_base(t, 16, "illegal hexadecimal integer");
+			case:
+				seen_point = false;
+				scan_mantissa(t, 10);
+				if t.ch == '.' {
+					seen_point = true;
+					if scan_fraction(t) {
+						check_end = false;
+					}
+				}
+				if check_end {
+					scan_exponent(t);
+					check_end = false;
+				}
+			}
+		}
+	}
+
+	if check_end {
+		scan_mantissa(t, 10);
+
+		if !scan_fraction(t) {
+			scan_exponent(t);
+		}
+	}
+
+	return .Number, string(t.src[offset : t.offset]);
+}
+
+scan_punct :: proc(t: ^Tokenizer, ch: rune) -> (kind: Token_Kind) {
+	kind = .Punct;
+	switch ch {
+	case:
+		kind = .Invalid;
+
+	case '<', '>':
+		if t.ch == ch {
+			advance_rune(t);
+		}
+		if t.ch == '=' {
+			advance_rune(t);
+		}
+	case '!', '+', '-', '*', '/', '%', '^', '=':
+		if t.ch == '=' {
+			advance_rune(t);
+		}
+	case '#':
+		if t.ch == '#' {
+			advance_rune(t);
+		}
+	case '&':
+		if t.ch == '=' || t.ch == '&' {
+			advance_rune(t);
+		}
+	case '|':
+		if t.ch == '=' || t.ch == '|' {
+			advance_rune(t);
+		}
+	case '(', ')', '[', ']', '{', '}':
+		// okay
+	case '~', ',', ':', ';', '?':
+		// okay
+	case '`':
+		// okay
+	case '.':
+		if t.ch == '.' && peek(t) == '.' {
+			advance_rune(t);
+			advance_rune(t); // consume last '.'
+		}
+	}
+	return;
+}
+
+peek :: proc(t: ^Tokenizer) -> byte {
+	if t.read_offset < len(t.src) {
+		return t.src[t.read_offset];
+	}
+	return 0;
+}
+peek_str :: proc(t: ^Tokenizer, str: string) -> bool {
+	if t.read_offset < len(t.src) {
+		return strings.has_prefix(string(t.src[t.offset:]), str);
+	}
+	return false;
+}
+
+scan_literal_prefix :: proc(t: ^Tokenizer, str: string, prefix: ^string) -> bool {
+	if peek_str(t, str) {
+		offset := t.offset;
+		for _ in str {
+			advance_rune(t);
+		}
+		prefix^ = string(t.src[offset:][:len(str)-1]);
+		return true;
+	}
+	return false;
+}
+
+
+allow_next_to_be_newline :: proc(t: ^Tokenizer) -> bool {
+	if t.ch == '\n' {
+		advance_rune(t);
+		return true;
+	} else if t.ch == '\r' && peek(t) == '\n' { // allow for MS-DOS style line endings
+		advance_rune(t); // \r
+		advance_rune(t); // \n
+		return true;
+	}
+	return false;
+}
+
+scan :: proc(t: ^Tokenizer, f: ^File) -> ^Token {
+	skip_whitespace(t);
+
+	offset := t.offset;
+
+	kind: Token_Kind;
+	lit: string;
+	prefix: string;
+
+	switch ch := t.ch; {
+	case scan_literal_prefix(t, `u8"`, &prefix):
+		kind = .String;
+		lit = scan_string(t);
+	case scan_literal_prefix(t, `u"`, &prefix):
+		kind = .String;
+		lit = scan_string(t);
+	case scan_literal_prefix(t, `L"`, &prefix):
+		kind = .String;
+		lit = scan_string(t);
+	case scan_literal_prefix(t, `U"`, &prefix):
+		kind = .String;
+		lit = scan_string(t);
+	case scan_literal_prefix(t, `u'`, &prefix):
+		kind = .Char;
+		lit = scan_rune(t);
+	case scan_literal_prefix(t, `L'`, &prefix):
+		kind = .Char;
+		lit = scan_rune(t);
+	case scan_literal_prefix(t, `U'`, &prefix):
+		kind = .Char;
+		lit = scan_rune(t);
+
+	case is_ident0(ch):
+		lit = scan_identifier(t);
+		kind = .Ident;
+	case '0' <= ch && ch <= '9':
+		kind, lit = scan_number(t, false);
+	case:
+		advance_rune(t);
+		switch ch {
+		case -1:
+			kind = .EOF;
+		case '\\':
+			kind = .Punct;
+			if allow_next_to_be_newline(t) {
+				t.at_bol = true;
+				t.has_space = false;
+				return scan(t, f);
+			}
+
+		case '.':
+			if is_digit(t.ch) {
+				kind, lit = scan_number(t, true);
+			} else {
+				kind = scan_punct(t, ch);
+			}
+		case '"':
+			kind = .String;
+			lit = scan_string(t);
+		case '\'':
+			kind = .Char;
+			lit = scan_rune(t);
+		case '/':
+			if t.ch == '/' || t.ch == '*' {
+				kind = .Comment;
+				lit = scan_comment(t);
+				t.has_space = true;
+				break;
+			}
+			fallthrough;
+		case:
+			kind = scan_punct(t, ch);
+			if kind == .Invalid && ch != utf8.RUNE_BOM {
+				error_offset(t, t.offset, "illegal character '%r': %d", ch, ch);
+			}
+		}
+	}
+
+	if lit == "" {
+		lit = string(t.src[offset : t.offset]);
+	}
+
+	if kind == .Comment {
+		return scan(t, f);
+	}
+
+	tok := new(Token);
+	tok.kind = kind;
+	tok.lit = lit;
+	tok.pos = offset_to_pos(t, offset);
+	tok.file = f;
+	tok.prefix = prefix;
+	tok.at_bol = t.at_bol;
+	tok.has_space = t.has_space;
+
+	t.at_bol, t.has_space = false, false;
+
+	return tok;
+}
+
+tokenize :: proc(t: ^Tokenizer, f: ^File) -> ^Token {
+	setup_tokenizer: {
+		t.src = f.src;
+		t.ch = ' ';
+		t.offset = 0;
+		t.read_offset = 0;
+		t.line_offset = 0;
+		t.line_count = len(t.src) > 0 ? 1 : 0;
+		t.error_count = 0;
+		t.path = f.name;
+
+
+		advance_rune(t);
+		if t.ch == utf8.RUNE_BOM {
+			advance_rune(t);
+		}
+	}
+
+
+	t.at_bol = true;
+	t.has_space = false;
+
+	head: Token;
+	curr := &head;
+	for {
+		tok := scan(t, f);
+		if tok == nil {
+			break;
+		}
+		curr.next = tok;
+		curr = curr.next;
+		if tok.kind == .EOF {
+			break;
+		}
+	}
+
+	return head.next;
+}
+
+add_new_file :: proc(t: ^Tokenizer, name: string, src: []byte, id: int) -> ^File {
+	file := new(File);
+	file.id = id;
+	file.src = src;
+	file.name = name;
+	file.display_name = name;
+	return file;
+}
+
+tokenize_file :: proc(t: ^Tokenizer, path: string, id: int, loc := #caller_location) -> ^Token {
+	src, ok := os.read_entire_file(path);
+	if !ok {
+		return nil;
+	}
+	return tokenize(t, add_new_file(t, path, src, id));
+}
+
+
+inline_tokenize :: proc(t: ^Tokenizer, tok: ^Token, src: []byte) -> ^Token {
+	file := new(File);
+	file.src = src;
+	if tok.file != nil {
+		file.id = tok.file.id;
+		file.name = tok.file.name;
+		file.display_name = tok.file.name;
+	}
+
+	return tokenize(t, file);
+}
diff --git a/core/c/frontend/tokenizer/unicode.odin b/core/c/frontend/tokenizer/unicode.odin
new file mode 100644
index 000000000..41c48eb73
--- /dev/null
+++ b/core/c/frontend/tokenizer/unicode.odin
@@ -0,0 +1,116 @@
+package c_frontend_tokenizer
+
+
+in_range :: proc(range: []rune, c: rune) -> bool #no_bounds_check {
+	for i := 0; range[i] != -1; i += 2 {
+		if range[i] <= c && c <= range[i+1] {
+			return true;
+		}
+	}
+	return false;
+}
+
+
+// [https://www.sigbus.info/n1570#D] C11 allows ASCII and some multibyte characters in certan Unicode ranges to be used in an identifier.
+//
+// is_ident0 returns true if a given character is acceptable as the first character of an identifier.
+is_ident0 :: proc(c: rune) -> bool {
+	return in_range(_range_ident0, c);
+}
+// is_ident0 returns true if a given character is acceptable as a non-first character of an identifier.
+is_ident1 :: proc(c: rune) -> bool {
+	return is_ident0(c) || in_range(_range_ident1, c);
+}
+
+// Returns the number of columns needed to display a given character in a fixed-width font.
+// Based on https://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
+char_width :: proc(c: rune) -> int {
+	switch {
+	case in_range(_range_width0, c):
+		return 0;
+	case in_range(_range_width2, c):
+		return 2;
+	}
+	return 1;
+}
+
+display_width :: proc(str: string) -> (w: int) {
+	for c in str {
+		w += char_width(c);
+	}
+	return;
+}
+
+
+
+_range_ident0 := []rune{
+	'_', '_', 'a', 'z', 'A', 'Z', '$', '$',
+	0x00A8, 0x00A8, 0x00AA, 0x00AA, 0x00AD, 0x00AD, 0x00AF, 0x00AF,
+	0x00B2, 0x00B5, 0x00B7, 0x00BA, 0x00BC, 0x00BE, 0x00C0, 0x00D6,
+	0x00D8, 0x00F6, 0x00F8, 0x00FF, 0x0100, 0x02FF, 0x0370, 0x167F,
+	0x1681, 0x180D, 0x180F, 0x1DBF, 0x1E00, 0x1FFF, 0x200B, 0x200D,
+	0x202A, 0x202E, 0x203F, 0x2040, 0x2054, 0x2054, 0x2060, 0x206F,
+	0x2070, 0x20CF, 0x2100, 0x218F, 0x2460, 0x24FF, 0x2776, 0x2793,
+	0x2C00, 0x2DFF, 0x2E80, 0x2FFF, 0x3004, 0x3007, 0x3021, 0x302F,
+	0x3031, 0x303F, 0x3040, 0xD7FF, 0xF900, 0xFD3D, 0xFD40, 0xFDCF,
+	0xFDF0, 0xFE1F, 0xFE30, 0xFE44, 0xFE47, 0xFFFD,
+	0x10000, 0x1FFFD, 0x20000, 0x2FFFD, 0x30000, 0x3FFFD, 0x40000, 0x4FFFD,
+	0x50000, 0x5FFFD, 0x60000, 0x6FFFD, 0x70000, 0x7FFFD, 0x80000, 0x8FFFD,
+	0x90000, 0x9FFFD, 0xA0000, 0xAFFFD, 0xB0000, 0xBFFFD, 0xC0000, 0xCFFFD,
+	0xD0000, 0xDFFFD, 0xE0000, 0xEFFFD,
+	-1,
+};
+
+_range_ident1 := []rune{
+	'0', '9', '$', '$', 0x0300, 0x036F, 0x1DC0, 0x1DFF, 0x20D0, 0x20FF, 0xFE20, 0xFE2F,
+	-1,
+};
+
+
+_range_width0 := []rune{
+	0x0000, 0x001F, 0x007f, 0x00a0, 0x0300, 0x036F, 0x0483, 0x0486,
+	0x0488, 0x0489, 0x0591, 0x05BD, 0x05BF, 0x05BF, 0x05C1, 0x05C2,
+	0x05C4, 0x05C5, 0x05C7, 0x05C7, 0x0600, 0x0603, 0x0610, 0x0615,
+	0x064B, 0x065E, 0x0670, 0x0670, 0x06D6, 0x06E4, 0x06E7, 0x06E8,
+	0x06EA, 0x06ED, 0x070F, 0x070F, 0x0711, 0x0711, 0x0730, 0x074A,
+	0x07A6, 0x07B0, 0x07EB, 0x07F3, 0x0901, 0x0902, 0x093C, 0x093C,
+	0x0941, 0x0948, 0x094D, 0x094D, 0x0951, 0x0954, 0x0962, 0x0963,
+	0x0981, 0x0981, 0x09BC, 0x09BC, 0x09C1, 0x09C4, 0x09CD, 0x09CD,
+	0x09E2, 0x09E3, 0x0A01, 0x0A02, 0x0A3C, 0x0A3C, 0x0A41, 0x0A42,
+	0x0A47, 0x0A48, 0x0A4B, 0x0A4D, 0x0A70, 0x0A71, 0x0A81, 0x0A82,
+	0x0ABC, 0x0ABC, 0x0AC1, 0x0AC5, 0x0AC7, 0x0AC8, 0x0ACD, 0x0ACD,
+	0x0AE2, 0x0AE3, 0x0B01, 0x0B01, 0x0B3C, 0x0B3C, 0x0B3F, 0x0B3F,
+	0x0B41, 0x0B43, 0x0B4D, 0x0B4D, 0x0B56, 0x0B56, 0x0B82, 0x0B82,
+	0x0BC0, 0x0BC0, 0x0BCD, 0x0BCD, 0x0C3E, 0x0C40, 0x0C46, 0x0C48,
+	0x0C4A, 0x0C4D, 0x0C55, 0x0C56, 0x0CBC, 0x0CBC, 0x0CBF, 0x0CBF,
+	0x0CC6, 0x0CC6, 0x0CCC, 0x0CCD, 0x0CE2, 0x0CE3, 0x0D41, 0x0D43,
+	0x0D4D, 0x0D4D, 0x0DCA, 0x0DCA, 0x0DD2, 0x0DD4, 0x0DD6, 0x0DD6,
+	0x0E31, 0x0E31, 0x0E34, 0x0E3A, 0x0E47, 0x0E4E, 0x0EB1, 0x0EB1,
+	0x0EB4, 0x0EB9, 0x0EBB, 0x0EBC, 0x0EC8, 0x0ECD, 0x0F18, 0x0F19,
+	0x0F35, 0x0F35, 0x0F37, 0x0F37, 0x0F39, 0x0F39, 0x0F71, 0x0F7E,
+	0x0F80, 0x0F84, 0x0F86, 0x0F87, 0x0F90, 0x0F97, 0x0F99, 0x0FBC,
+	0x0FC6, 0x0FC6, 0x102D, 0x1030, 0x1032, 0x1032, 0x1036, 0x1037,
+	0x1039, 0x1039, 0x1058, 0x1059, 0x1160, 0x11FF, 0x135F, 0x135F,
+	0x1712, 0x1714, 0x1732, 0x1734, 0x1752, 0x1753, 0x1772, 0x1773,
+	0x17B4, 0x17B5, 0x17B7, 0x17BD, 0x17C6, 0x17C6, 0x17C9, 0x17D3,
+	0x17DD, 0x17DD, 0x180B, 0x180D, 0x18A9, 0x18A9, 0x1920, 0x1922,
+	0x1927, 0x1928, 0x1932, 0x1932, 0x1939, 0x193B, 0x1A17, 0x1A18,
+	0x1B00, 0x1B03, 0x1B34, 0x1B34, 0x1B36, 0x1B3A, 0x1B3C, 0x1B3C,
+	0x1B42, 0x1B42, 0x1B6B, 0x1B73, 0x1DC0, 0x1DCA, 0x1DFE, 0x1DFF,
+	0x200B, 0x200F, 0x202A, 0x202E, 0x2060, 0x2063, 0x206A, 0x206F,
+	0x20D0, 0x20EF, 0x302A, 0x302F, 0x3099, 0x309A, 0xA806, 0xA806,
+	0xA80B, 0xA80B, 0xA825, 0xA826, 0xFB1E, 0xFB1E, 0xFE00, 0xFE0F,
+	0xFE20, 0xFE23, 0xFEFF, 0xFEFF, 0xFFF9, 0xFFFB, 0x10A01, 0x10A03,
+	0x10A05, 0x10A06, 0x10A0C, 0x10A0F, 0x10A38, 0x10A3A, 0x10A3F, 0x10A3F,
+	0x1D167, 0x1D169, 0x1D173, 0x1D182, 0x1D185, 0x1D18B, 0x1D1AA, 0x1D1AD,
+	0x1D242, 0x1D244, 0xE0001, 0xE0001, 0xE0020, 0xE007F, 0xE0100, 0xE01EF,
+	-1,
+};
+
+_range_width2 := []rune{
+	0x1100, 0x115F, 0x2329, 0x2329, 0x232A, 0x232A, 0x2E80, 0x303E,
+	0x3040, 0xA4CF, 0xAC00, 0xD7A3, 0xF900, 0xFAFF, 0xFE10, 0xFE19,
+	0xFE30, 0xFE6F, 0xFF00, 0xFF60, 0xFFE0, 0xFFE6, 0x1F000, 0x1F644,
+	0x20000, 0x2FFFD, 0x30000, 0x3FFFD,
+	-1,
+};