[go] runtime: add a test for issue 78081

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Keith Randall (Gerrit)

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12:19 PM (6 hours ago) 12:19 PM

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Keith Randall submitted the change

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Commit message:

runtime: add a test for issue 78081

Contrive to have a bunch of stack shrinking going on during
memclrNoHeapPointersPreemptible calls.

Fails at tip with this patch:

--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -2184,6 +2184,7 @@ func reusableSize(size uintptr) bool {
 // Use this with care; if the data being cleared is tagged to contain
 // pointers, this allows the GC to run before it is all cleared.
 func memclrNoHeapPointersChunked(size uintptr, x unsafe.Pointer) {
+       y := uintptr(x)
        if getg().preempt {
                // TODO: no need for this, except to test that
                // the preemption point is ok for small zeroings.
@@ -2193,6 +2194,7 @@ func memclrNoHeapPointersChunked(size uintptr, x unsafe.Pointer) {
                // may hold locks, e.g., profiling
                goschedguarded()
        }
+       x = unsafe.Pointer(y)
        // got this from benchmarking. 128k is too small, 512k is too large.
        const chunkBytes = 256 * 1024
        for size > chunkBytes {

Update #78081