Hi
I find the conditional expression, "long NSOTLimit = (AbsPosLimit < LONG_MIN) ? (long)LONG_MIN : (long)AbsPosLimit;" could cause incorrect results.
AbsPosLimit is composed of AbsoluteCounter and IncPosLimit.
long long AbsPosLimit = (long long)AbsoluteCounter + (long long)IncPosLimit;
There are two cases to discuss :
Case 1
There are the calculation results of below codes :
AbsPosLimit = 8426644
NSOTLimit = LONG_MIN = -2147483648 (not expected)
AbsPosLimit is greater than LONG_MIN, so the value of NSOTLimit shouldn't be LONG_MIN. NSOTLimit is expected to be equal to AbsPosLimit.
#define LONG_MIN 0xFFFFFFFF80000000 //-2147483648
long AbsoluteCounter = 108397879;
long IncPosLimit = -99971235;
// calculate absolute position limit. use LL to check overflow
long long AbsPosLimit = (long long)AbsoluteCounter + (long long)IncPosLimit;
// if AbsPosLimit < LONG_MIN means overflow
long NSOTLimit = (AbsPosLimit < LONG_MIN) ? (long)LONG_MIN : (long)AbsPosLimit;
Case 2
To figure out the problem in Case 1, I try to set
long AbsoluteCounter = 99971234;
long IncPosLimit = -99971235;
Then I get the results :
AbsPosLimit = -1
NSOTLimit = -1 (expected)
The testing results show the correct value of NSOTLimit.
How can I explain why I can't get correct NSOTLimit result in Case 1 by executing the same conditional expression?
Thank you!
