add commets to mulOverflow

Signed-off-by: fzhedu <fzhedu@gmail.com>
pingcap · May 19, 2022 · 6448bdc · 6448bdc
1 parent 8944eaf
commit 6448bdc
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/libs/libcommon/include/common/arithmeticOverflow.h b/libs/libcommon/include/common/arithmeticOverflow.h
@@ -116,6 +116,8 @@ inline bool mulOverflow(__int128 x, __int128 y, __int128 & res)
     return res/x != y; /// whether overflow int128
 }
 
+/// Int256 doesn't use the complement representation to express negative values, but uses an extra bit to express the sign flag,
+/// the actual range of Int256 is from -(2^256 - 1) to 2^256 - 1, so 2^255 ~ 2^256-1 do not overflow Int256.
 template <>
 inline bool mulOverflow(Int256 x, Int256 y, Int256 & res)
 {