I have been told that the flex scanner won't return empty strings, so
strlen(data) should always be greater 0. To avoid a hard to debug issue
though, add an assert() to make sure this is always the case before
risking an unsigned variable underrun.
A real issue though is the check for 'datalen - 1 >= 0', which will
never fail due to datalen being unsigned. Fix this by incrementing both
sides by one, hence checking 'datalen >= 1'.
Signed-off-by: Phil Sutter <phil@xxxxxx>
---
Changes since v1:
- Based on the assumption that strlen(data) should never be less than 1,
just add an assert() to be on the safe side.
- By modifying the '>= 0' check a bit, we can get by without making
datalen a signed variable.
---
src/evaluate.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/src/evaluate.c b/src/evaluate.c
index 7eb28f2c4b72d..fb9b82534d520 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -221,6 +221,7 @@ static int expr_evaluate_string(struct eval_ctx *ctx, struct expr **exprp)
memset(data + len, 0, data_len - len);
mpz_export_data(data, expr->value, BYTEORDER_HOST_ENDIAN, len);
+ assert(strlen(data) > 0);
datalen = strlen(data) - 1;
if (data[datalen] != '*') {
/* We need to reallocate the constant expression with the right
@@ -234,7 +235,7 @@ static int expr_evaluate_string(struct eval_ctx *ctx, struct expr **exprp)
return 0;
}
- if (datalen - 1 >= 0 &&
+ if (datalen >= 1 &&
data[datalen - 1] == '\\') {
char unescaped_str[data_len];
--
2.8.2
--
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