[Tarantool-patches] [PATCH v4 02/16] sql: fix possible undefined behavior during cast

[imeevma at tarantool.org]

This patch fixes possible undefined behavior during the implicit cast of
INTEGER to DOUBLE. The problem is, if the INTEGER is close enough to
2^64, it will be cast to 2^64 when it is cast to DOUBLE. Since we have a
check for loss of precision, this will cause this DOUBLE to be cast to
an INTEGER, which will result in undefined behavior since this DOUBLE is
outside the range of INTEGER.
---
 src/box/sql/mem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
index 89b99a183..99ac4d8e7 100644
--- a/src/box/sql/mem.c
+++ b/src/box/sql/mem.c
@@ -682,7 +682,7 @@ uint_to_double_precise(struct Mem *mem)
 	assert(mem->type == MEM_TYPE_UINT);
 	double d;
 	d = (double)mem->u.u;
-	if (mem->u.u != (uint64_t)d)
+	if (d == (double)UINT64_MAX || mem->u.u != (uint64_t)d)
 		return -1;
 	mem->u.r = d;
 	mem->flags = 0;
-- 
2.25.1