runtime: zero freed memory

aykevl · aykevl · commit 8d929ada3c07 · 2023-01-10T21:02:59.000+01:00
This helps to find bugs in the GC. It does have a performance impact so
it's only enabled when asserts are enabled.
diff --git a/src/runtime/gc_blocks.go b/src/runtime/gc_blocks.go
@@ -168,6 +168,9 @@ func (b gcBlock) markFree() {
 	if gcAsserts && b.state() != blockStateFree {
 		runtimePanic("gc: markFree() was not successful")
 	}
+	if gcAsserts {
+		*(*[wordsPerBlock]uintptr)(unsafe.Pointer(b.address())) = [wordsPerBlock]uintptr{}
+	}
 }
 
 // unmark changes the state of the block from mark to head. It must be marked

Original file line number	Diff line number	Diff line change
`@@ -168,6 +168,9 @@ func (b gcBlock) markFree() {`
`168`	`168`	`if gcAsserts && b.state() != blockStateFree {`
`169`	`169`	`runtimePanic("gc: markFree() was not successful")`
`170`	`170`	`}`
	`171`	`+ if gcAsserts {`
	`172`	`+ ([wordsPerBlock]uintptr)(unsafe.Pointer(b.address())) = [wordsPerBlock]uintptr{}`
	`173`	`+ }`
`171`	`174`	`}`
`172`	`175`
`173`	`176`	`// unmark changes the state of the block from mark to head. It must be marked`