If you have a loop like:
for i := range slice {
f(&i)
}
There's no way to know whether f launches a goroutine that captures the
loop variable without also evaluating the body of f and potentially every
function directly or indirectly called by f. If i escapes into a global
variable, you also have to evaluate the entire program to see if a
goroutine is ever launched which could access i by way of that
variable. This is what they mean by whole program analysis.
However, I feel like only catching a go or defer statement which is the
last statement in the loop body is very far from a best effort. I also
wonder if the analysis could take advantage of the existing escape analysis
in the compiler to flag likely misuses of loop variables. There are
certainly valid use cases for loop variables escaping (such as when this
coincides with returning from the function or otherwise breaking the loop),
so I'm not sure how easy it would be to discriminate, even if it's feasible
to begin with.
On Thu, Aug 10, 2017 at 1:18 PM <spen...@justin.tv> wrote:
> I've noticed that cmd/vet's rangeloop check, which warns you about binding
> to range loop variables in function literals which are launched with 'go'
> or 'defer', is more limited than I thought:
>
>
> https://github.com/golang/go/blob/d5ad7793d610bddfb3e7e09b8dafa0b0837f0cb2/src/cmd/vet/rangeloop.go#L6-L9
>
>
> <https://github.com/golang/go/blob/d5ad7793d610bddfb3e7e09b8dafa0b0837f0cb2/src/cmd/vet/rangeloop.go#L6-L9>
>
>> This file contains the code to check range loop variables bound inside
>> function literals that are deferred or launched in new goroutines. We only
>> check instances where the defer or go statement is the last statement in
>> the loop body, as otherwise we would need whole program analysis.
>>
>
> I don't understand why whole program analysis is necessary here. Why can't
> cmd/vet check each function literal declared within the loop's braces?
>
> --
> You received this message because you are subscribed to the Google Groups
> "golang-nuts" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to golang-nuts+unsubscr...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.
>
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
