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on freeze, unmap mapped containers

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It turns out that calling syscall.Munmap() is a thing which
can change any container holding a pointer into the mapped space,
but which wouldn't detect frozen containers. So we need to
copy storage for such things. This negates some of the memory
wins of the rowcache code, but makes it not crashy.
This commit is contained in:
Seebs 2019-05-31 16:17:06 -05:00
parent 636f132564
commit 973579e662
1 changed files with 10 additions and 1 deletions
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11
roaring/container_stash.go
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@ -256,11 +256,20 @@ func (c *Container) setMapped(mapped bool) {
}
// Freeze returns an unmodifiable container identical to c. This might
// be c, now marked unmodifiable, or might be a new container.
// be c, now marked unmodifiable, or might be a new container. If c
// is currently marked as "mapped", referring to a backing store that's
// not a conventional Go pointer, the storage may be copied.
func (c *Container) Freeze() *Container {
if c == nil {
return nil
}
// don't need to freeze
if c.flags&flagFrozen != 0 {
return c
}
// unmapOrClone should unmap-in-place because the existing
// container isn't frozen (or we'd already have returned it).
c = c.unmapOrClone()
c.flags |= flagFrozen
return c
}