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ptrguard: simplify pointer size assert 

Signed-off-by: Sven Anderson <sven@redhat.com>
This commit is contained in:
Sven Anderson 2021-10-02 14:17:55 +09:00 committed by mergify[bot]
parent a451da9e8e
commit 3210885d21
1 changed files with 4 additions and 4 deletions
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8
internal/cutil/ptrguard.go
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@ -60,10 +60,10 @@ func (v *PtrGuard) Release() {
// The uintptrPtr() helper function below assumes that uintptr has the same size
// as a pointer, although in theory it could be larger. Therefore we use this
// constant expression to assert size equality as a safeguard at compile time.
// How it works: the difference of both sizes is converted into an 8 bit value
// and left-bit-shifted by 8. This always creates an overflow error at compile
// time, if the difference of the sizes is not 0.
const _ = uint8(unsafe.Sizeof(uintptr(0))-PtrSize) << 8 // size assert
// How it works: if sizes are different, either the inner or outer expression is
// negative, which always fails with "constant ... overflows uintptr", because
// unsafe.Sizeof() is a uintptr typed constant.
const _ = -(unsafe.Sizeof(uintptr(0)) - PtrSize) // size assert
func uintptrPtr(p *CPtr) *uintptr {
return (*uintptr)(unsafe.Pointer(p))
}