Selected changes:
- This release improves the performance of most uses of defer to incur almost zero overhead compared to calling the deferred function directly. As a result, defer can now be used in performance-critical code without overhead concerns.
- Goroutines are now asynchronously preemptible. As a result, loops without function calls no longer potentially deadlock the scheduler or significantly delay garbage collection.
- Per the overlapping interfaces proposal, Go 1.14 now permits embedding of interfaces with overlapping method sets: methods from an embedded interface may have the same names and identical signatures as methods already present in the (embedding) interface. This solves problems that typically (but not exclusively) occur with diamond-shaped embedding graphs. Explicitly declared methods in an interface must remain unique, as before.
What does that mean in practice? Can I perform expensive calculations in parallel exhausting all cores?
package main
import (
"time"
"runtime"
)
func main(){
for i := runtime.NumCPU(); i > 0; i-- {
go func() {
for {}
}()
}
time.Sleep(time.Second)
println("bye")
}For example, as of now, the standard release note url for 1.14 currently 404s: https://golang.org/doc/go1.14
Anyone happen to know why there used to be overhead here/what changed?
From my comfortable sofa, it seems that there should be little difference between a defer-ed and direct call?
The full design doc is here: https://github.com/golang/proposal/blob/master/design/34481-...
> Go 1.13 implements the defer statement by calling into the runtime to push a "defer object" onto the defer chain. Then, in any function that contains defer statements, the compiler inserts a call to runtime.deferreturn at every function exit point to unwind that function's defers.
> We propose optimizing deferred calls in functions where every defer is executed at most once (specifically, a defer may be on a conditional path, but is never in a loop in the control-flow graph). In this optimization, the compiler assigns a bit for every defer site to indicate whether that defer had been reached or not. The defer statement itself simply sets the corresponding bit and stores all necessary arguments in specific stack slots. Then, at every exit point of the function, the compiler open-codes each deferred call, protected by (and clearing) each corresponding bit.
The more I use it, the more I enjoy Go. Having grown up with the healthy dose of Pascal and later Modula 2, I appreciate many traits of Go which let me just focus on the tasks at hand. With very little "magic" going on, some parts of the code might be a bit tedious, but you also always have the feeling of being in control, as everything is very explicit. Add to that a few underapreciated dynamic features. I am first of all a professional Lisp/Scheme programmer and a lot of Scheme concepts translate surprisingly well into Go due to having first class functions and a garbage collector.
It is very nice to see how the Go releases are very careful to add new features while continuosly improve on the "quality" side. Enhancing the performance of "defer" is a great example. Like unwind-protect in Lisp, it is a very elegant way to ensure that cleanup code is run under any circumstance. Removing its overhead is a big thing.
The warning flag patch allows you to do:
go build -gcflags=-warnunused
go test -gcflags=-warnunused
$ go test -gcflags=-warnunused
# github.com/kstenerud/go-describe
./describe_unsafe.go:8:2: Warning: imported and not used: "fmt"
./describe.go:329:2: Warning: isInUnsignedArray declared but not used
...
PASS
ok github.com/kstenerud/go-describe 0.002s
Thank you! Modules and vendoring has been a royal pain. This should help a lot.
I feel like it's generally possible to work around this by creating a wrapper struct with an overridden MarshalJSON method? But maybe that's infeasible for deeply nested structs.
That's the crux of my issue. If it was only for a single, un-nested field then it would be trivial.
I am currently solving it by walking through the whole struct, but that is not-ideal.
To argue in its favor tho, file-hosting and site-serving may be handled by different systems with different security characteristics, and potentially even different datacenters (e.g. a CDN). If you only have to compromise one system, it's generally easier to do so than when you have to compromise N and make them all agree with each other.
This is a legitimate case as it's happened to other projects in the past.
That's pretty aggressive. Dropping support for a major OS that is only 1 year old.