proposal: cmd/vet: magic comment to check that variable is stack allocated

[earthboundkid]

Go doesn't directly allow for heap vs. stack allocation, but this is critical to ensuring high performance. You can check that variables are properly stack allocated by asking Go to report what escapes to the heap with -gcflags "-m" but this is a manual process. I propose adding a magic comment that go vet will use to check whether the variable ought to be stack allocated.

The comment should have no actual effect on escape analysis. It will merely create a visible error if something is not allocated as intended.

[randall77]

You can write a test using AllocsPerRun in the testing package, to ensure that some function doesn't allocate more than you expect. Is that insufficient somehow?

[earthboundkid]

That’s a good question. I see this mostly as a convenience feature to make it more simple.

This would also be per variable rather than per function.

[rsc]

Go vet is about detecting common mistakes.
It is out of scope to start designing vet-specific annotations and/or type-checking,
and it is also out of scope to tie anything in vet to a single compiler.

[rsc]

Based on the discussion above, this seems like a likely decline.

[rsc]

No change in consensus, so declined.