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ros::Time and ros::Duration don't respect TIME_MAX and DURATION_MAX in arethmetic operators #120

Closed fabmene closed 4 years ago

fabmene commented 4 years ago

roscpp_core/rostime/src/time.cpp defines TIME_MIN, TIME_MAX, DURATION_MIN and DURATION_MAX with std::numeric_limits. Performing arithmetic operations on them throws an exception due to causing an overflow.

From a user's standpoint however, I would expect ros::Time::now() + ros::DURATION_MAX == ros::TIME_MAX

Is there a design reason why this is not implemented?

dirk-thomas commented 4 years ago

From a user's standpoint however, I would expect ros::Time::now() + ros::DURATION_MAX == ros::TIME_MAX

I am not sure I share this expectation. For now() being zero I might agree but for anything else I would consider this to be an overflow which an exception seems appropriate for.

fabmene commented 4 years ago

Maybe I misunderstand the use of these constants. I intended to use DURATION_MAX as resembling an infinite duration and understood TIME_MAX to represent a point of time infinitely far into the future.

Basically I expected a representation for an infinite duration that works with the ros::Time and ros::Duration arithmetics and doesn't require me to check for overflows in the process.

dirk-thomas commented 4 years ago

As other constants ending in _MAX these values describe the largest value which can be stored in the data type. They certainly do not represent infinity.

So in order to check overflows you have to catch exceptions.

Assuming this answered your question I will go ahead and close this ticket.