testing: benchmark timeout when benchtime set too long

[lkxiaolou]

What version of Go are you using (go version)?

go1.15

Does this issue reproduce with the latest release?

yes

What did you do?

When benchmark function execute time is very short, set benchtime=5s / 10s / 20s is ok.

BenchmarkNewObject-2            1000000000               0.279 ns/op

But set benchtime=120s will execute time out.

*** Test killed with quit: ran too long (11m0s).

What did you expect to see?

Do not timeout

What did you see instead?

*** Test killed with quit: ran too long (11m0s).

[gopherbot]

Change https://golang.org/cl/369294 mentions this issue: Fix #49973 benchmark timeout when benchtime set too long

[seankhliao]

Duplicate of #12446

[lkxiaolou]

Duplicate of #12446

Not the same, see #49974, int64 overflow, may be a bug

[mvdan]

I agree that this might not be a duplicate - the code doesn't seem to be safe against overflows.

That said, the fix doesn't seem complete. Not all overflows will result in negative numbers.

[lkxiaolou]

I agree that this might not be a duplicate - the code doesn't seem to be safe against overflows.

That said, the fix doesn't seem complete. Not all overflows will result in negative numbers.

Sorry, Is there any other cases?

[mvdan]

https://go.dev/play/p/MBFpdZOOSgx

That example also has some better overflow detection that you can enable and try for yourself.

Note that there are multiple operations involved in testing/benchmark.go, including multiplications and additions. Proper overflow checking won't be as trivial as in my example.

[mvdan]

Also, a fix would need to come with a test :)