Cannot pass immutable value as inout argument

JetForMe · 2018-01-16T21:10:00.000Z

Is it not possible for Swift to treat C API const pointers as something that can take let arguments?

LGS_EXPORT bool lgs_notify(struct lgs_context_t* ctx, const lgs_notify_params_t* params);
.
.
.
let p = lgs_notify_params_t(...)
lgs_notify(self.ctx, &p)
^Cannot pass immutable value as inout argument: 'p' is a 'let' constant

Why isn't the "const" in the C declaration enough to let Swift know it's const and just allow it to be a let?

···

--
Rick Mann
rmann@latencyzero.com

jrose · 2018-01-16T21:22:34.000Z

You can do this if you don't write '&', which incorporates the caveat that you're not passing a stable address. But please file a bug anyway, because the diagnostic should tell you that!

Jordan

···

On Jan 16, 2018, at 13:10, Rick Mann via swift-users <swift-users@swift.org> wrote:

Is it not possible for Swift to treat C API const pointers as something that can take let arguments?

LGS_EXPORT bool lgs_notify(struct lgs_context_t* ctx, const lgs_notify_params_t* params);
.
.
.
let p = lgs_notify_params_t(...)
lgs_notify(self.ctx, &p)
^Cannot pass immutable value as inout argument: 'p' is a 'let' constant

Why isn't the "const" in the C declaration enough to let Swift know it's const and just allow it to be a let?

--
Rick Mann
rmann@latencyzero.com

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swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

DevAndArtist · 2018-01-16T21:20:00.000Z

I don’t know how C API is imported, btus INOUT parameter must be mutable, this is a language artifact.

···

Am 16. Januar 2018 um 22:10:13, Rick Mann via swift-users (swift-users@swift.org) schrieb:

Is it not possible for Swift to treat C API const pointers as something that can take let arguments?

LGS_EXPORT bool lgs_notify(struct lgs_context_t* ctx, const lgs_notify_params_t* params);
.
.
.
let p = lgs_notify_params_t(...)
lgs_notify(self.ctx, &p)
^Cannot pass immutable value as inout argument: 'p' is a 'let' constant

Why isn't the "const" in the C declaration enough to let Swift know it's const and just allow it to be a let?

--
Rick Mann
rmann@latencyzero.com

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

JetForMe · 2018-01-17T00:37:28.000Z

Xcode can't properly parse the C header to show me the Swift signature, but if I try calling it like this:

let p = lgs_notify_params_t(notify: lgs_notify_did_enter_background)
lgs_notify(self.ctx, p)

I get this error:

Cannot convert value of type 'lgs_notify_params_t' to expected argument type 'UnsafePointer<lgs_notify_params_t>!'

···

On Jan 16, 2018, at 13:22 , Jordan Rose <jordan_rose@apple.com> wrote:

You can do this if you don't write '&', which incorporates the caveat that you're not passing a stable address. But please file a bug anyway, because the diagnostic should tell you that!

Jordan

On Jan 16, 2018, at 13:10, Rick Mann via swift-users <swift-users@swift.org> wrote:

Is it not possible for Swift to treat C API const pointers as something that can take let arguments?

LGS_EXPORT bool lgs_notify(struct lgs_context_t* ctx, const lgs_notify_params_t* params);
.
.
.
let p = lgs_notify_params_t(...)
lgs_notify(self.ctx, &p)
^Cannot pass immutable value as inout argument: 'p' is a 'let' constant

Why isn't the "const" in the C declaration enough to let Swift know it's const and just allow it to be a let?

--
Rick Mann
rmann@latencyzero.com

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

--
Rick Mann
rmann@latencyzero.com

jrose · 2018-01-17T00:38:35.000Z

Oh no, you're right, I'm sorry. You can only do that with arrays at the moment. We do have a bug for this already.

Jordan

···

On Jan 16, 2018, at 16:37, Roderick Mann <rmann@latencyzero.com> wrote:

Xcode can't properly parse the C header to show me the Swift signature, but if I try calling it like this:

   let p = lgs_notify_params_t(notify: lgs_notify_did_enter_background)
   lgs_notify(self.ctx, p)

I get this error:

Cannot convert value of type 'lgs_notify_params_t' to expected argument type 'UnsafePointer<lgs_notify_params_t>!'

On Jan 16, 2018, at 13:22 , Jordan Rose <jordan_rose@apple.com> wrote:

You can do this if you don't write '&', which incorporates the caveat that you're not passing a stable address. But please file a bug anyway, because the diagnostic should tell you that!

Jordan

On Jan 16, 2018, at 13:10, Rick Mann via swift-users <swift-users@swift.org> wrote:

Is it not possible for Swift to treat C API const pointers as something that can take let arguments?

LGS_EXPORT bool lgs_notify(struct lgs_context_t* ctx, const lgs_notify_params_t* params);
.
.
.
let p = lgs_notify_params_t(...)
lgs_notify(self.ctx, &p)
                   ^Cannot pass immutable value as inout argument: 'p' is a 'let' constant

Why isn't the "const" in the C declaration enough to let Swift know it's const and just allow it to be a let?

--
Rick Mann
rmann@latencyzero.com

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

--
Rick Mann
rmann@latencyzero.com <mailto:rmann@latencyzero.com>

Geordie_J · 2018-01-18T00:18:30.000Z

Oh no, you're right, I'm sorry. You can only do that with arrays at the
moment. We do have a bug for this already.

Jordan

But couldn’t you call it like this:

lgs_notify_params_t(notify: [lgs_notify_did_enter_background])

For exactly that reason?

- Geordie

···

Jordan Rose via swift-users <swift-users@swift.org> schrieb am Mi. 17. Jan. 2018 um 01:38:

On Jan 16, 2018, at 16:37, Roderick Mann <rmann@latencyzero.com> wrote:

Xcode can't properly parse the C header to show me the Swift signature,
but if I try calling it like this:

   let p = lgs_notify_params_t(notify: lgs_notify_did_enter_background)
   lgs_notify(self.ctx, p)

I get this error:

Cannot convert value of type 'lgs_notify_params_t' to expected argument
type 'UnsafePointer<lgs_notify_params_t>!'

On Jan 16, 2018, at 13:22 , Jordan Rose <jordan_rose@apple.com> wrote:

You can do this if you don't write '&', which incorporates the caveat that
you're not passing a stable address. But please file a bug anyway, because
the diagnostic should tell you that!

Jordan

On Jan 16, 2018, at 13:10, Rick Mann via swift-users < > swift-users@swift.org> wrote:

Is it not possible for Swift to treat C API const pointers as something
that can take let arguments?

LGS_EXPORT bool lgs_notify(struct lgs_context_t* ctx, const
lgs_notify_params_t* params);
.
.
.
let p = lgs_notify_params_t(...)
lgs_notify(self.ctx, &p)
                   ^Cannot pass immutable value as inout argument: 'p' is
a 'let' constant

Why isn't the "const" in the C declaration enough to let Swift know it's
const and just allow it to be a let?

--
Rick Mann
rmann@latencyzero.com

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

--
Rick Mann
rmann@latencyzero.com

_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users