SE-0107 states that UnsafePointer.withMemoryRebound(to:capacity:) should produce
a const UnsafePointer, but the implementation that I committed in Whitney
produces an UnsafeMutablePointer.
As a result Swift 3 accepts code, that we would like to reject:
func takesUInt(_: UnsafeMutablePointer<UInt>) {}
func takesConstUInt(_: UnsafePointer<UInt>) {}
func foo(p: UnsafePointer<Int>) {
p.withMemoryRebound(to: UInt.self, capacity: 1) {
takesUInt($0) // <========= implicitly converts to a mutable pointer
takesConstUInt($0)
}
}
We would like to reject this in favor of:
func takesUInt(_: UnsafeMutablePointer<UInt>) {}
func takesConstUInt(_: UnsafePointer<UInt>) {}
func foo(p: UnsafePointer<Int>) {
p.withMemoryRebound(to: UInt.self, capacity: 1) {
takesUInt(UnsafeMutablePointer(mutating: $0))
takesConstUInt($0)
}
}
This looks to me like an experimental change accidentally creeped onto my branch
and it was hard to spot in .gyb code. I needed to write the unit test
in terms of UnsafeMutablePointer in order to use expectType, so didn't
catch this.
rdar://28409842 UnsafePointer.withMemoryRebound(to:capacity:) incorrectly produces a mutable pointer argument
This decreases total testing time by over a minute on my old Mac Pro.
It probably has much less effect on systems with fewer cores, but shouldn't
be any worse there.
Swift SVN r22745
The syntax being reverted added busywork and noise to the common case
where you want to say "I have the right address, but the wrong type,"
without adding any real safety.
Also it eliminated the ability to write UnsafePointer<T>(otherPointer),
without adding ".self" to T. Overall, it was not a win.
This reverts commits r21324 and r21342
Swift SVN r21424
Previously, it was possible to write Unsafe[Mutable]Pointer(x) and have
Swift deduce the pointee type based on context. Since reinterpreting
memory is a fundamentally type-unsafe operation, it's better to be
explicit about conversions from Unsafe[Mutable]Pointer<T> to
Unsafe[Mutable]Pointer<U>. This change is consistent with the move from
reinterpretCast(x) to unsafeBitCast(x, T.self).
Also, we've encoded the operations of explicitly adding or removing
mutability as properties, so that adding mutability can be separated
from wild reinterpretCast'ing, a much more severe form of unsafety.
Swift SVN r21324
The test harness now can recover after test crashes, allowing:
- check for crashes themselves (without reporting them to the Python lit driver,
which is about 10x slower -- even if CrashTracer is disabled);
- recover from unexpected test crashes and run the rest of the tests;
- this lays the groundwork for assertions that end the test execution, but
allow the rest of the tests to run (rdar://17906801).
Note that we don't spawn a fresh process for every test. We create a child
process and reuse it until it crashes.
Swift SVN r21090
