[PATCH 1/3] char.c: Fix parsing of escapes

[PATCH 1/3] char.c: Fix parsing of escapes

[Ramsay Jones]

When parsing a string or character constant, the parse_escape()
function returns a pointer to the character at which to resume
parsing. However, in the case of an hex or octal escape, it was
returning a one-past-the-end pointer. Thus, a string like:

    char str[3] = "\x61\x62\x63";

was being parsed as:

    '\x61', 'x', '6', '2', '\x63'

which, in turn, provokes an 'too long initializer' warning.

Also, fix an off-by-one error in get_char_constant() when setting
the 'end' pointer for a TOKEN_CHAR or TOKEN_WIDE_CHAR. Despite the
name, the string->length of the token is actually the size of the
allocated memory (ie len+1), so we need to compensate by using
'token->string->length - 1'.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
---
 char.c               |  9 ++++++---
 validation/escapes.c | 12 ++++++++++++
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/char.c b/char.c
index 6a46a11..08ca223 100644
--- a/char.c
+++ b/char.c
@@ -27,9 +27,10 @@ static const char *parse_escape(const char *p, unsigned *val, const char *end, i
 	case 'x': {
 		unsigned mask = -(1U << (bits - 4));
 		for (c = 0; p < end; c = (c << 4) + d) {
-			d = hexval(*p++);
+			d = hexval(*p);
 			if (d > 16)
 				break;
+			p++;
 			if (c & mask) {
 				warning(pos,
 					"hex escape sequence out of range");
@@ -42,8 +43,10 @@ static const char *parse_escape(const char *p, unsigned *val, const char *end, i
 		if (p + 2 < end)
 			end = p + 2;
 		c -= '0';
-		while (p < end && (d = *p++ - '0') < 8)
+		while (p < end && (d = *p - '0') < 8) {
 			c = (c << 3) + d;
+			p++;
+		}
 		if ((c & 0400) && bits < 9)
 			warning(pos,
 				"octal escape sequence out of range");
@@ -65,7 +68,7 @@ void get_char_constant(struct token *token, unsigned long long *val)
 	case TOKEN_CHAR:
 	case TOKEN_WIDE_CHAR:
 		p = token->string->data;
-		end = p + token->string->length;
+		end = p + token->string->length - 1;
 		break;
 	case TOKEN_CHAR_EMBEDDED_0 ... TOKEN_CHAR_EMBEDDED_3:
 		end = p + type - TOKEN_CHAR;
diff --git a/validation/escapes.c b/validation/escapes.c
index 4a1b030..5f526b9 100644
--- a/validation/escapes.c
+++ b/validation/escapes.c
@@ -4,6 +4,16 @@ static int e[] = { '\'', '\"', '\?', '\\',
 static char *s = "\'\"\?\\ \a\b\f\n\r\t\v \377\xcafe";
 
 static int bad_e[] = { '\c', '\0123', '\789', '\xdefg' };
+
+static char a_hex[3] = "\x61\x62\x63";
+static char b_hex[3] = "\x61\x62\x63\x64";
+static char c_hex[3] = "\x61\x62";
+static char d_hex[3] = "\x61";
+
+static char a_oct[3] = "\141\142\143";
+static char b_oct[3] = "\141\142\143\144";
+static char c_oct[3] = "\141\142";
+static char d_oct[3] = "\141";
 /*
  * check-name: Character escape sequences
  *
@@ -16,5 +26,7 @@ escapes.c:6:30: warning: multi-character character constant
 escapes.c:6:39: warning: multi-character character constant
 escapes.c:6:47: warning: hex escape sequence out of range
 escapes.c:6:47: warning: multi-character character constant
+escapes.c:9:24: warning: too long initializer-string for array of char
+escapes.c:14:24: warning: too long initializer-string for array of char
  * check-error-end
  */
-- 
1.8.2

Re: [PATCH 1/3] char.c: Fix parsing of escapes

[Christopher Li]

On 05/16/2013 12:41 PM, Ramsay Jones wrote:
> 
> When parsing a string or character constant, the parse_escape()
> function returns a pointer to the character at which to resume
> parsing. However, in the case of an hex or octal escape, it was
> returning a one-past-the-end pointer. Thus, a string like:
> 
>     char str[3] = "\x61\x62\x63";
> 
> was being parsed as:
> 
>     '\x61', 'x', '6', '2', '\x63'
> 
> which, in turn, provokes an 'too long initializer' warning.
> 
> Also, fix an off-by-one error in get_char_constant() when setting
> the 'end' pointer for a TOKEN_CHAR or TOKEN_WIDE_CHAR. Despite the
> name, the string->length of the token is actually the size of the
> allocated memory (ie len+1), so we need to compensate by using
> 'token->string->length - 1'.

Great patch. Applied.

Chris