Summary

Escape analysis incorrectly skips instrumentation for pointer dereferences when the pointer variable itself doesn't escape, but the memory it points to can be shared.

Reported by

@thepudds in golang/go#6508 (comment)

Reproduction

//go:noinline
func update(ptr *int) { // -gcflags=-m: "ptr does not escape"
    *ptr++
}

func main() {
    var shared int
    var wg sync.WaitGroup
    for range 2 {
        wg.Go(func() {
            for range 100 {
                update(&shared)
            }
        })
    }
    wg.Wait()
}

Expected

Race detected on *ptr++ (TSAN reports correctly)

Actual

No race reported (v0.8.1)

Root Cause

Our escape analysis skips instrumentation when a variable "doesn't escape", but:

• ptr is a local parameter (doesn't escape)
• *ptr dereferences to shared which IS accessed by multiple goroutines

Fix

Only skip direct local variable access (x = 5), NOT pointer dereferences (*ptr = 5).

Pointer dereferences must always be instrumented regardless of escape analysis.

Priority

P0 - Critical regression in v0.8.0