[PATCH] config.c: fix potential number truncation in git_parse_signed()

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

clang -Wabsolute-value on IA-32 architecture complains that "absolute
value function 'labs' given an argument of type 'intmax_t' (aka 'long
long') but has parameter of type 'long' which may cause truncation of
value". Very unlikely for this code though. Nevertheless, add an
explicit check for truncation to shut clang up and error out.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 config.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/config.c b/config.c
index d7ce34b..880bd4a 100644
--- a/config.c
+++ b/config.c
@@ -503,6 +503,7 @@ static int git_parse_signed(const char *value, intmax_t *ret, intmax_t max)
 		intmax_t val;
 		uintmax_t uval;
 		uintmax_t factor = 1;
+		long int lival;
 
 		errno = 0;
 		val = strtoimax(value, &end, 0);
@@ -512,9 +513,14 @@ static int git_parse_signed(const char *value, intmax_t *ret, intmax_t max)
 			errno = EINVAL;
 			return 0;
 		}
-		uval = labs(val);
+		lival = (long int)val;
+		if (lival != val) {
+			errno = ERANGE;
+			return 0;
+		}
+		uval = labs(lival);
 		uval *= factor;
-		if (uval > max || labs(val) > uval) {
+		if (uval > max || labs(lival) > uval) {
 			errno = ERANGE;
 			return 0;
 		}
-- 
2.8.2.532.g6dfa503.dirty