[adrian_b]

One should always measure to see if there is a noticeable slowdown or not.

That is what I have meant by "an extremely serious reason to do otherwise".

For many programs the speed is determined by things like the throughput or latency of accessing the main memory, or by I/O operations, or by interaction with an user, in which case the sanitize options have negligible influence on speed.

When necessary, they should be turned off only for specific well tested functions whose performance is limited by CPU computation in registers or in cache memory, and they should remain on for the rest of the program.

[jeffbee]

ASAN can easily slow your program by 100x or worse. Your bias should always be that its impact would not be acceptable in production. If you were willing to accept the cost of ASAN you should have simply chose a slower, safer language in the first place.