copy universal character parsing from lexer
[cparser] / lexer.c
diff --git a/lexer.c b/lexer.c
index 6bafd8b..1f0c23d 100644 (file)
--- a/lexer.c
+++ b/lexer.c
@@ -108,16 +108,17 @@ static inline void put_back(utf32 const pc)
 
 static inline void next_char(void);
 
-#define MATCH_NEWLINE(code)  \
-       case '\r':               \
-               next_char();         \
-               if (c == '\n') {     \
-       case '\n':               \
-                       next_char();     \
-               }                    \
-               lexer_pos.lineno++;  \
+#define NEWLINE  \
+       '\r': \
+               next_char(); \
+               if (c == '\n') { \
+       case '\n': \
+                       next_char(); \
+               } \
+               lexer_pos.lineno++; \
                lexer_pos.colno = 1; \
-               code
+               goto newline; \
+               newline // Let it look like an ordinary case label.
 
 #define eat(c_type) (assert(c == c_type), next_char())
 
@@ -126,7 +127,8 @@ static void maybe_concat_lines(void)
        eat('\\');
 
        switch (c) {
-       MATCH_NEWLINE(return;)
+       case NEWLINE:
+               return;
 
        default:
                break;
@@ -179,13 +181,12 @@ static inline void next_char(void)
        }
 }
 
-#define SYMBOL_CHARS  \
-       case '$': if (!allow_dollar_in_symbol) goto dollar_sign; \
+#define SYMBOL_CHARS_WITHOUT_E_P \
+            '$': if (!allow_dollar_in_symbol) goto dollar_sign; \
        case 'a':         \
        case 'b':         \
        case 'c':         \
        case 'd':         \
-       case 'e':         \
        case 'f':         \
        case 'g':         \
        case 'h':         \
@@ -196,7 +197,6 @@ static inline void next_char(void)
        case 'm':         \
        case 'n':         \
        case 'o':         \
-       case 'p':         \
        case 'q':         \
        case 'r':         \
        case 's':         \
@@ -211,7 +211,6 @@ static inline void next_char(void)
        case 'B':         \
        case 'C':         \
        case 'D':         \
-       case 'E':         \
        case 'F':         \
        case 'G':         \
        case 'H':         \
@@ -222,7 +221,6 @@ static inline void next_char(void)
        case 'M':         \
        case 'N':         \
        case 'O':         \
-       case 'P':         \
        case 'Q':         \
        case 'R':         \
        case 'S':         \
@@ -233,10 +231,20 @@ static inline void next_char(void)
        case 'X':         \
        case 'Y':         \
        case 'Z':         \
-       case '_':
+       case '_'
+
+#define SYMBOL_CHARS_E_P \
+            'E': \
+       case 'P': \
+       case 'e': \
+       case 'p'
+
+#define SYMBOL_CHARS  \
+            SYMBOL_CHARS_WITHOUT_E_P: \
+       case SYMBOL_CHARS_E_P
 
 #define DIGITS        \
-       case '0':         \
+            '0':         \
        case '1':         \
        case '2':         \
        case '3':         \
@@ -245,7 +253,98 @@ static inline void next_char(void)
        case '6':         \
        case '7':         \
        case '8':         \
-       case '9':
+       case '9'
+
+static bool is_universal_char_valid(utf32 const v)
+{
+       /* C11 ยง6.4.3:2 */
+       if (v < 0xA0U && v != 0x24 && v != 0x40 && v != 0x60)
+               return false;
+       if (0xD800 <= v && v <= 0xDFFF)
+               return false;
+       return true;
+}
+
+static int digit_value(utf32 digit);
+
+static utf32 parse_universal_char(unsigned const n_digits)
+{
+       utf32 v = 0;
+       for (unsigned k = n_digits; k != 0; --k) {
+               if (isxdigit(c)) {
+                       v = 16 * v + digit_value(c);
+                       next_char();
+               } else {
+                       errorf(&lexer_pos, "short universal character name, expected %u more digits", k);
+                       break;
+               }
+       }
+       if (!is_universal_char_valid(v)) {
+               errorf(&lexer_pos, "\\%c%0*X is not a valid universal character name", n_digits == 4 ? 'u' : 'U', (int)n_digits, v);
+       }
+       return v;
+}
+
+static bool is_universal_char_valid_identifier(utf32 const v)
+{
+       /* C11 Annex D.1 */
+       if (                v == 0x000A8) return true;
+       if (                v == 0x000AA) return true;
+       if (                v == 0x000AD) return true;
+       if (                v == 0x000AF) return true;
+       if (0x000B2 <= v && v <= 0x000B5) return true;
+       if (0x000B7 <= v && v <= 0x000BA) return true;
+       if (0x000BC <= v && v <= 0x000BE) return true;
+       if (0x000C0 <= v && v <= 0x000D6) return true;
+       if (0x000D8 <= v && v <= 0x000F6) return true;
+       if (0x000F8 <= v && v <= 0x000FF) return true;
+       if (0x00100 <= v && v <= 0x0167F) return true;
+       if (0x01681 <= v && v <= 0x0180D) return true;
+       if (0x0180F <= v && v <= 0x01FFF) return true;
+       if (0x0200B <= v && v <= 0x0200D) return true;
+       if (0x0202A <= v && v <= 0x0202E) return true;
+       if (0x0203F <= v && v <= 0x02040) return true;
+       if (                v == 0x02054) return true;
+       if (0x02060 <= v && v <= 0x0206F) return true;
+       if (0x02070 <= v && v <= 0x0218F) return true;
+       if (0x02460 <= v && v <= 0x024FF) return true;
+       if (0x02776 <= v && v <= 0x02793) return true;
+       if (0x02C00 <= v && v <= 0x02DFF) return true;
+       if (0x02E80 <= v && v <= 0x02FFF) return true;
+       if (0x03004 <= v && v <= 0x03007) return true;
+       if (0x03021 <= v && v <= 0x0302F) return true;
+       if (0x03031 <= v && v <= 0x0303F) return true;
+       if (0x03040 <= v && v <= 0x0D7FF) return true;
+       if (0x0F900 <= v && v <= 0x0FD3D) return true;
+       if (0x0FD40 <= v && v <= 0x0FDCF) return true;
+       if (0x0FDF0 <= v && v <= 0x0FE44) return true;
+       if (0x0FE47 <= v && v <= 0x0FFFD) return true;
+       if (0x10000 <= v && v <= 0x1FFFD) return true;
+       if (0x20000 <= v && v <= 0x2FFFD) return true;
+       if (0x30000 <= v && v <= 0x3FFFD) return true;
+       if (0x40000 <= v && v <= 0x4FFFD) return true;
+       if (0x50000 <= v && v <= 0x5FFFD) return true;
+       if (0x60000 <= v && v <= 0x6FFFD) return true;
+       if (0x70000 <= v && v <= 0x7FFFD) return true;
+       if (0x80000 <= v && v <= 0x8FFFD) return true;
+       if (0x90000 <= v && v <= 0x9FFFD) return true;
+       if (0xA0000 <= v && v <= 0xAFFFD) return true;
+       if (0xB0000 <= v && v <= 0xBFFFD) return true;
+       if (0xC0000 <= v && v <= 0xCFFFD) return true;
+       if (0xD0000 <= v && v <= 0xDFFFD) return true;
+       if (0xE0000 <= v && v <= 0xEFFFD) return true;
+       return false;
+}
+
+static bool is_universal_char_valid_identifier_start(utf32 const v)
+{
+       /* C11 Annex D.2 */
+       if (0x0300 <= v && v <= 0x036F) return false;
+       if (0x1DC0 <= v && v <= 0x1DFF) return false;
+       if (0x20D0 <= v && v <= 0x20FF) return false;
+       if (0xFE20 <= v && v <= 0xFE2F) return false;
+       return true;
+}
 
 /**
  * Read a symbol from the input and build
@@ -253,17 +352,42 @@ static inline void next_char(void)
  */
 static void parse_symbol(void)
 {
-       obstack_1grow(&symbol_obstack, (char) c);
-       next_char();
-
        while (true) {
                switch (c) {
-               DIGITS
-               SYMBOL_CHARS
+               case DIGITS:
+               case SYMBOL_CHARS:
                        obstack_1grow(&symbol_obstack, (char) c);
                        next_char();
                        break;
 
+               case '\\':
+                       next_char();
+                       switch (c) {
+                       {
+                               unsigned n;
+                       case 'U': n = 8; goto universal;
+                       case 'u': n = 4; goto universal;
+universal:
+                               next_char();
+                               utf32 const v = parse_universal_char(n);
+                               if (!is_universal_char_valid_identifier(v)) {
+                                       if (is_universal_char_valid(v)) {
+                                               errorf(&lexer_pos, "universal character \\%c%0*X is not valid in an identifier", n == 4 ? 'u' : 'U', (int)n, v);
+                                       }
+                               } else if (obstack_object_size(&symbol_obstack) == 0 && !is_universal_char_valid_identifier_start(v)) {
+                                       errorf(&lexer_pos, "universal character \\%c%0*X is not valid as start of an identifier", n == 4 ? 'u' : 'U', (int)n, v);
+                               } else {
+                                       obstack_grow_utf8(&symbol_obstack, v);
+                               }
+                               break;
+                       }
+
+                       default:
+                               put_back(c);
+                               c = '\\';
+                               goto end_symbol;
+                       }
+
                default:
 dollar_sign:
                        goto end_symbol;
@@ -284,8 +408,12 @@ end_symbol:
        }
 }
 
-static string_t identify_string(char *string, size_t len)
+static string_t sym_make_string(string_encoding_t const enc)
 {
+       obstack_1grow(&symbol_obstack, '\0');
+       size_t const len    = obstack_object_size(&symbol_obstack) - 1;
+       char  *const string = obstack_finish(&symbol_obstack);
+
        /* TODO hash */
 #if 0
        const char *result = strset_insert(&stringset, concat);
@@ -295,132 +423,32 @@ static string_t identify_string(char *string, size_t len)
 #else
        const char *result = string;
 #endif
-       return (string_t) {result, len};
+       return (string_t){ result, len, enc };
 }
 
-/**
- * parse suffixes like 'LU' or 'f' after numbers
- */
-static void parse_number_suffix(void)
+static void parse_pp_number(void)
 {
-       assert(obstack_object_size(&symbol_obstack) == 0);
-       while (true) {
+       for (;;) {
                switch (c) {
-               SYMBOL_CHARS
-                       obstack_1grow(&symbol_obstack, (char) c);
-                       next_char();
-                       break;
-               default:
-               dollar_sign:
-                       goto finish_suffix;
-               }
-       }
-finish_suffix:
-       if (obstack_object_size(&symbol_obstack) == 0) {
-               lexer_token.number.suffix.begin = NULL;
-               lexer_token.number.suffix.size  = 0;
-               return;
-       }
-
-       obstack_1grow(&symbol_obstack, '\0');
-       size_t size   = obstack_object_size(&symbol_obstack) - 1;
-       char  *string = obstack_finish(&symbol_obstack);
-
-       lexer_token.number.suffix = identify_string(string, size);
-}
-
-static void parse_exponent(void)
-{
-       if (c == '-' || c == '+') {
-               obstack_1grow(&symbol_obstack, (char)c);
-               next_char();
-       }
-
-       if (isdigit(c)) {
-               do {
+               case SYMBOL_CHARS_E_P:
                        obstack_1grow(&symbol_obstack, (char)c);
                        next_char();
-               } while (isdigit(c));
-       } else {
-               errorf(&lexer_token.base.source_position, "exponent has no digits");
-       }
-}
-
-/**
- * Parses a hex number including hex floats and set the
- * lexer_token.
- */
-static void parse_number_hex(void)
-{
-       bool is_float   = false;
-       bool has_digits = false;
-
-       while (isxdigit(c)) {
-               has_digits = true;
-               obstack_1grow(&symbol_obstack, (char) c);
-               next_char();
-       }
-
-       if (c == '.') {
-               is_float = true;
-               obstack_1grow(&symbol_obstack, (char) c);
-               next_char();
+                       if (c == '+' || c == '-') {
+               case '.':
+               case DIGITS:
+               case SYMBOL_CHARS_WITHOUT_E_P:
+                               obstack_1grow(&symbol_obstack, (char)c);
+                               next_char();
+                       }
+                       break;
 
-               while (isxdigit(c)) {
-                       has_digits = true;
-                       obstack_1grow(&symbol_obstack, (char) c);
-                       next_char();
+               default:
+dollar_sign:
+                       lexer_token.kind           = T_NUMBER;
+                       lexer_token.literal.string = sym_make_string(STRING_ENCODING_CHAR);
+                       return;
                }
        }
-       if (c == 'p' || c == 'P') {
-               is_float = true;
-               obstack_1grow(&symbol_obstack, (char) c);
-               next_char();
-               parse_exponent();
-       } else if (is_float) {
-               errorf(&lexer_token.base.source_position,
-                      "hexadecimal floatingpoint constant requires an exponent");
-       }
-       obstack_1grow(&symbol_obstack, '\0');
-
-       size_t  size   = obstack_object_size(&symbol_obstack) - 1;
-       char   *string = obstack_finish(&symbol_obstack);
-       lexer_token.number.number = identify_string(string, size);
-
-       lexer_token.kind = is_float ? T_FLOATINGPOINT : T_INTEGER;
-
-       if (!has_digits) {
-               errorf(&lexer_token.base.source_position, "invalid number literal '%S'", &lexer_token.number.number);
-               lexer_token.number.number.begin = "0";
-               lexer_token.number.number.size  = 1;
-       }
-
-       parse_number_suffix();
-}
-
-static void parse_number_bin(void)
-{
-       bool has_digits = false;
-
-       while (c == '0' || c == '1') {
-               has_digits = true;
-               obstack_1grow(&symbol_obstack, (char)c);
-               next_char();
-       }
-       obstack_1grow(&symbol_obstack, '\0');
-
-       size_t  const size   = obstack_object_size(&symbol_obstack) - 1;
-       char   *const string = obstack_finish(&symbol_obstack);
-       lexer_token.number.number = identify_string(string, size);
-       lexer_token.kind          = T_INTEGER;
-
-       if (!has_digits) {
-               errorf(&lexer_token.base.source_position, "invalid number literal '%S'", &lexer_token.number.number);
-               lexer_token.number.number.begin = "0";
-               lexer_token.number.number.size  = 1;
-       }
-
-       parse_number_suffix();
 }
 
 /**
@@ -433,85 +461,6 @@ static bool is_octal_digit(utf32 chr)
        return '0' <= chr && chr <= '7';
 }
 
-/**
- * Parses a number and sets the lexer_token.
- */
-static void parse_number(void)
-{
-       bool is_float   = false;
-       bool has_digits = false;
-
-       assert(obstack_object_size(&symbol_obstack) == 0);
-       if (c == '0') {
-               obstack_1grow(&symbol_obstack, (char)c);
-               next_char();
-               if (c == 'x' || c == 'X') {
-                       obstack_1grow(&symbol_obstack, (char)c);
-                       next_char();
-                       parse_number_hex();
-                       return;
-               } else if (c == 'b' || c == 'B') {
-                       /* GCC extension: binary constant 0x[bB][01]+.  */
-                       obstack_1grow(&symbol_obstack, (char)c);
-                       next_char();
-                       parse_number_bin();
-                       return;
-               }
-               has_digits = true;
-       }
-
-       while (isdigit(c)) {
-               has_digits = true;
-               obstack_1grow(&symbol_obstack, (char) c);
-               next_char();
-       }
-
-       if (c == '.') {
-               is_float = true;
-               obstack_1grow(&symbol_obstack, '.');
-               next_char();
-
-               while (isdigit(c)) {
-                       has_digits = true;
-                       obstack_1grow(&symbol_obstack, (char) c);
-                       next_char();
-               }
-       }
-       if (c == 'e' || c == 'E') {
-               is_float = true;
-               obstack_1grow(&symbol_obstack, 'e');
-               next_char();
-               parse_exponent();
-       }
-
-       obstack_1grow(&symbol_obstack, '\0');
-       size_t  size   = obstack_object_size(&symbol_obstack) - 1;
-       char   *string = obstack_finish(&symbol_obstack);
-       lexer_token.number.number = identify_string(string, size);
-
-       if (is_float) {
-               lexer_token.kind = T_FLOATINGPOINT;
-       } else {
-               lexer_token.kind = T_INTEGER;
-
-               if (string[0] == '0') {
-                       /* check for invalid octal digits */
-                       for (size_t i= 0; i < size; ++i) {
-                               char t = string[i];
-                               if (t >= '8')
-                                       errorf(&lexer_token.base.source_position, "invalid digit '%c' in octal number", t);
-                       }
-               }
-       }
-
-       if (!has_digits) {
-               errorf(&lexer_token.base.source_position, "invalid number literal '%S'",
-                      &lexer_token.number.number);
-       }
-
-       parse_number_suffix();
-}
-
 /**
  * Returns the value of a digit.
  * The only portable way to do it ...
@@ -620,10 +569,10 @@ static utf32 parse_escape_sequence(void)
                if (c_mode & _GNUC)
                        return 27;   /* hopefully 27 is ALWAYS the code for ESCAPE */
                break;
-       case 'u':
-       case 'U':
-               parse_error("universal character parsing not implemented yet");
-               return EOF;
+
+       case 'U': return parse_universal_char(8);
+       case 'u': return parse_universal_char(4);
+
        default:
                break;
        }
@@ -634,66 +583,13 @@ static utf32 parse_escape_sequence(void)
 
 string_t make_string(const char *string)
 {
-       size_t      len   = strlen(string) + 1;
-       char *const space = obstack_alloc(&symbol_obstack, len);
-       memcpy(space, string, len);
-
-       return identify_string(space, len);
+       obstack_grow(&symbol_obstack, string, strlen(string));
+       return sym_make_string(STRING_ENCODING_CHAR);
 }
 
-/**
- * Parse a string literal and set lexer_token.
- */
-static void parse_string_literal(string_encoding_t const enc)
+static void parse_string(utf32 const delim, token_kind_t const kind, string_encoding_t const enc, char const *const context)
 {
-       eat('"');
-
-       while (true) {
-               switch (c) {
-               case '\\': {
-                       utf32 const tc = parse_escape_sequence();
-                       if (tc >= 0x100) {
-                               warningf(WARN_OTHER, &lexer_pos, "escape sequence out of range");
-                       }
-                       obstack_1grow(&symbol_obstack, tc);
-                       break;
-               }
-
-               case EOF:
-                       errorf(&lexer_token.base.source_position, "string has no end");
-                       goto end_of_string;
-
-               case '"':
-                       next_char();
-                       goto end_of_string;
-
-               default:
-                       obstack_grow_symbol(&symbol_obstack, c);
-                       next_char();
-                       break;
-               }
-       }
-
-end_of_string:
-
-       /* TODO: concatenate multiple strings separated by whitespace... */
-
-       /* add finishing 0 to the string */
-       obstack_1grow(&symbol_obstack, '\0');
-       size_t const size   = (size_t)obstack_object_size(&symbol_obstack) - 1;
-       char        *string = obstack_finish(&symbol_obstack);
-
-       lexer_token.kind            = T_STRING_LITERAL;
-       lexer_token.string.encoding = enc;
-       lexer_token.string.string   = identify_string(string, size);
-}
-
-/**
- * Parse a character constant and set lexer_token.
- */
-static void parse_character_constant(string_encoding_t const enc)
-{
-       eat('\'');
+       eat(delim);
 
        while (true) {
                switch (c) {
@@ -705,42 +601,51 @@ static void parse_character_constant(string_encoding_t const enc)
                                }
                                obstack_1grow(&symbol_obstack, tc);
                        } else {
-                               obstack_grow_symbol(&symbol_obstack, tc);
+                               obstack_grow_utf8(&symbol_obstack, tc);
                        }
                        break;
                }
 
-               MATCH_NEWLINE(
-                       parse_error("newline while parsing character constant");
+               case NEWLINE:
+                       errorf(&lexer_pos, "newline while parsing %s", context);
                        break;
-               )
-
-               case '\'':
-                       next_char();
-                       goto end_of_char_constant;
 
                case EOF:
-                       errorf(&lexer_token.base.source_position, "EOF while parsing character constant");
-                       goto end_of_char_constant;
+                       errorf(&lexer_token.base.source_position, "EOF while parsing %s", context);
+                       goto end_of_string;
 
                default:
-                       obstack_grow_symbol(&symbol_obstack, c);
-                       next_char();
-                       break;
-
+                       if (c == delim) {
+                               next_char();
+                               goto end_of_string;
+                       } else {
+                               obstack_grow_utf8(&symbol_obstack, c);
+                               next_char();
+                               break;
+                       }
                }
        }
 
-end_of_char_constant:;
-       obstack_1grow(&symbol_obstack, '\0');
-       const size_t        size   = (size_t)obstack_object_size(&symbol_obstack)-1;
-       char         *const string = obstack_finish(&symbol_obstack);
+end_of_string:
+       lexer_token.kind           = kind;
+       lexer_token.literal.string = sym_make_string(enc);
+}
 
-       lexer_token.kind            = T_CHARACTER_CONSTANT;
-       lexer_token.string.encoding = enc;
-       lexer_token.string.string   = identify_string(string, size);
+/**
+ * Parse a string literal and set lexer_token.
+ */
+static void parse_string_literal(string_encoding_t const enc)
+{
+       parse_string('"', T_STRING_LITERAL, enc, "string literal");
+}
 
-       if (size == 0) {
+/**
+ * Parse a character constant and set lexer_token.
+ */
+static void parse_character_constant(string_encoding_t const enc)
+{
+       parse_string('\'', T_CHARACTER_CONSTANT, enc, "character constant");
+       if (lexer_token.literal.string.size == 0) {
                errorf(&lexer_token.base.source_position, "empty character constant");
        }
 }
@@ -767,7 +672,8 @@ static void skip_multiline_comment(void)
                        }
                        break;
 
-               MATCH_NEWLINE(break;)
+               case NEWLINE:
+                       break;
 
                case EOF: {
                        errorf(&lexer_token.base.source_position,
@@ -838,20 +744,26 @@ static void eat_until_newline(void)
  */
 static void parse_line_directive(void)
 {
-       if (pp_token.kind != T_INTEGER) {
+       if (pp_token.kind != T_NUMBER) {
                parse_error("expected integer");
        } else {
                /* use offset -1 as this is about the next line */
-               lexer_pos.lineno = atoi(pp_token.number.number.begin) - 1;
+               char      *end;
+               long const line = strtol(pp_token.literal.string.begin, &end, 0);
+               if (*end == '\0') {
+                       lexer_pos.lineno = line - 1;
+               } else {
+                       errorf(&lexer_pos, "'%S' is not a valid line number", &pp_token.literal.string);
+               }
                next_pp_token();
        }
-       if (pp_token.kind == T_STRING_LITERAL && pp_token.string.encoding == STRING_ENCODING_CHAR) {
-               lexer_pos.input_name = pp_token.string.string.begin;
+       if (pp_token.kind == T_STRING_LITERAL && pp_token.literal.string.encoding == STRING_ENCODING_CHAR) {
+               lexer_pos.input_name       = pp_token.literal.string.begin;
                lexer_pos.is_system_header = false;
                next_pp_token();
 
                /* attempt to parse numeric flags as outputted by gcc preprocessor */
-               while (pp_token.kind == T_INTEGER) {
+               while (pp_token.kind == T_NUMBER) {
                        /* flags:
                         * 1 - indicates start of a new file
                         * 2 - indicates return from a file
@@ -860,7 +772,7 @@ static void parse_line_directive(void)
                         *
                         * currently we're only interested in "3"
                         */
-                       if (streq(pp_token.number.number.begin, "3")) {
+                       if (streq(pp_token.literal.string.begin, "3")) {
                                lexer_pos.is_system_header = true;
                        }
                        next_pp_token();
@@ -968,7 +880,7 @@ static void parse_preprocessor_directive(void)
        case T_IDENTIFIER:
                parse_preprocessor_identifier();
                break;
-       case T_INTEGER:
+       case T_NUMBER:
                parse_line_directive();
                break;
        case '\n':
@@ -1026,12 +938,11 @@ void lexer_next_preprocessing_token(void)
                        next_char();
                        break;
 
-               MATCH_NEWLINE(
+               case NEWLINE:
                        lexer_token.kind = '\n';
                        return;
-               )
 
-               SYMBOL_CHARS {
+               case SYMBOL_CHARS: {
                        parse_symbol();
                        /* might be a wide string ( L"string" ) */
                        string_encoding_t const enc = STRING_ENCODING_WIDE;
@@ -1044,8 +955,8 @@ void lexer_next_preprocessing_token(void)
                        return;
                }
 
-               DIGITS
-                       parse_number();
+               case DIGITS:
+                       parse_pp_number();
                        return;
 
                case '"':
@@ -1058,10 +969,10 @@ void lexer_next_preprocessing_token(void)
 
                case '.':
                        MAYBE_PROLOG
-                               DIGITS
+                               case DIGITS:
                                        put_back(c);
                                        c = '.';
-                                       parse_number();
+                                       parse_pp_number();
                                        return;
 
                                case '.':
@@ -1168,6 +1079,17 @@ void lexer_next_preprocessing_token(void)
                        MAYBE('#', T_HASHHASH)
                        ELSE('#')
 
+               case '\\':
+                       next_char();
+                       if (c == 'U' || c == 'u') {
+                               put_back(c);
+                               c = '\\';
+                               parse_symbol();
+                       } else {
+                               lexer_token.kind = '\\';
+                       }
+                       return;
+
                case '?':
                case '[':
                case ']':
@@ -1178,7 +1100,6 @@ void lexer_next_preprocessing_token(void)
                case '~':
                case ';':
                case ',':
-               case '\\':
                        lexer_token.kind = c;
                        next_char();
                        return;
@@ -1189,7 +1110,7 @@ void lexer_next_preprocessing_token(void)
 
                default:
 dollar_sign:
-                       errorf(&lexer_pos, "unknown character '%c' found", c);
+                       errorf(&lexer_pos, "unknown character '%lc' found", c);
                        next_char();
                        break;
                }