testing: report allocations in the BenchmarkResult struct Stringer

[titpetric]

Please answer these questions before submitting your issue. Thanks!

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

1.10

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

Not applicable

What did you do?

Call testing.Benchmark when using b.ReportAllocs() in the benchmark function.

What did you expect to see?

New  1000000          1232 ns/op        0 B/op         0 allocs/op
A.New  1000000        1169 ns/op        0 B/op         0 allocs/op

What did you see instead?

New  1000000          1171 ns/op
A.New  1000000        1115 ns/op

[davecheney]

This is not the expected behaviour. Can you please provide the code sample that produced the output above.

[titpetric]

Sure, here is the playground link, crippled a bit to give you some output (ie, doesn't use b.N).

The sources for the func (r BenchmarkResult) String() string here basically don't give a call to r.MemString(), or have access to B.showAllocResult, because the *B or showAllocResult isn't copied into the struct (ie, there isn't a property for it, yet).

[davecheney]

Can you demonstrate this failure with a normal _test.go test? You don't need to use the playground.

…

On 7 March 2018 at 23:18, Tit Petric ***@***.***> wrote: Sure, here is the playground link <https://play.golang.org/p/xKnapThDcui>, crippled a bit to give you some output (ie, doesn't use b.N). The sources for the func (r BenchmarkResult) String() string here <https://golang.org/src/testing/benchmark.go?s=9060:9100#L324> basically don't give a call to r.MemString(), or have access to B.showAllocResult, because the *B or showAllocResult isn't copied into the struct. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#24296 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAcAz2JbxlLZ1zL_vqqVONsVzY0tyvUks5tb9AggaJpZM4SgVFJ> .

[davecheney]

Sorry, ignore my last request. This isn't a bug, this is a feature request.

…

On 7 March 2018 at 23:19, Dave Cheney ***@***.***> wrote: Can you demonstrate this failure with a normal _test.go test? You don't need to use the playground. On 7 March 2018 at 23:18, Tit Petric ***@***.***> wrote: > Sure, here is the playground link <https://play.golang.org/p/xKnapThDcui>, > crippled a bit to give you some output (ie, doesn't use b.N). > > The sources for the func (r BenchmarkResult) String() string here > <https://golang.org/src/testing/benchmark.go?s=9060:9100#L324> basically > don't give a call to r.MemString(), or have access to B.showAllocResult, > because the *B or showAllocResult isn't copied into the struct. > > — > You are receiving this because you commented. > Reply to this email directly, view it on GitHub > <#24296 (comment)>, or mute > the thread > <https://github.com/notifications/unsubscribe-auth/AAAcAz2JbxlLZ1zL_vqqVONsVzY0tyvUks5tb9AggaJpZM4SgVFJ> > . >

[titpetric]

Yes, feature request. It's an inconvenience with a work-around. Thanks for taking the time to understand it however :)

[andybons]

Yes, feature request. It's an inconvenience with a work-around.

Can you outline what your workaround is? I’m having trouble seeing it :)

[titpetric]

@andybons it's fmt.Println(result, result.MemString()) instead of just fmt.Println(result).

[ianlancetaylor]

I don't think we should always print the memory results, and I don't think we should add a new field to BenchmarkResult, a struct that currently has only exported fields. It's already possible to call MemString; adding the results to String would be a minor convenience in a few cases. So all in all I don't think this is worth doing. Sorry.