Add GATT Peripheral example for Pico W

ColemanCDA · November 18, 2024, 4:25pm

I've added a PR that demo the usage of Bluetooth for Embedded Swift. Adds a Pico W example to enable Bluetooth advertisements and GATT Peripheral functionality, advertising as an iBeacon in addition to its name and Bluetooth address. A custom GATT service and characteristic is exposed as read and write which toggles the GPIO LED state.

github.com/apple/swift-embedded-examples

Add GATT Peripheral example for Pico W

apple:main ← MillerTechnologyPeru:feature/pico-w-ble-peripheral

opened 04:22PM - 18 Nov 24 UTC

colemancda

+38609 -0

Updates the Pico W example to enable Bluetooth advertisements and GATT Periphera…l functionality, advertising as an iBeacon in addition to its name and Bluetooth address. A custom GATT service and characteristic is exposed as read and write which toggles the GPIO LED state. <img width="519" alt="Screenshot 2024-11-18 at 11 12 30 AM" src="https://github.com/user-attachments/assets/88054252-d2b7-405c-9f22-4279f834a5f4"> <img width="519" alt="Screenshot 2024-11-18 at 11 12 11 AM" src="https://github.com/user-attachments/assets/9c2c2227-2350-4b7c-b02e-3bde837dde2a">

ColemanCDA · November 18, 2024, 4:38pm

I had to deal with multiple obscure Swift compiler crashes and errors to get this working on the Pico W.

Synthesized Equatable conformance for enum with associated values (e.g. BluetoothUUID) somehow relies on String comparison and Unicode data tables. I made sure my code was not relying on Unicode and it turns out the synthesized code was emitting those dependencies. An explicit Equatable implementation or removing the protocol conformance fixes this.
A mutating subscript with private(set) just crashes the compiler at hasValidSignatureForEmbedded(). I had to change my subscript to a method.

When I have time I'll file the appropriate Swift bugs for these. @rauhul

rauhul · November 18, 2024, 4:40pm

Please do file issues for these 2 bugs! They are both extremely unexpected. cc @kubamracek

ColemanCDA · November 18, 2024, 5:03pm

github.com/swiftlang/swift

Synthesized `Equatable` conformance for enum with associated values uses String comparison

opened 04:52PM - 18 Nov 24 UTC

colemancda

bug triage needed

### Description While developing a Bluetooth LE peripheral for Embedded Swift o…n the Pico W, I came across unexpected compiler behavior. The compiler was emitting calls to `_stringCompareFastUTF8()`, which in turn relies on the Unicode data which I did not want to link due to code size. Adding an [explicit `Equatable` implementation](https://github.com/apple/swift-embedded-examples/pull/74/commits/e0e8857c2f662fb6a2f3fea5cc82d0d49f9486a9) for my enum solved this issue. ### Reproduction ```swift @frozen public enum BluetoothUUID: Hashable, Sendable { case bit16(UInt16) case bit32(UInt32) case bit128(UInt128) } ``` Links against `_stringCompareFastUTF8` and `_swift_stdlib_getNormData` Adding an explicit Equatable implementation removes the dependency on String. ``` extension BluetoothUUID: Equatable { public static func == (lhs: BluetoothUUID, rhs: BluetoothUUID) -> Bool { switch (lhs, rhs) { case let (.bit16(lhsValue), .bit16(rhsValue)): return lhsValue == rhsValue case let (.bit32(lhsValue), .bit32(rhsValue)): return lhsValue == rhsValue case let (.bit128(lhsValue), .bit128(rhsValue)): return lhsValue == rhsValue default: return false } } } ``` ### Expected behavior `Equatable` conformance for enums with associated values should not rely on any `String` or Unicode functions. ### Environment ``` Apple Swift version 6.1-dev (LLVM 9d655fdc6103926, Swift 0d16cbf5d5ef6f9) Target: arm64-apple-macosx14.0 ``` Targeting the Pico W with the following flags: ``` -target armv6m-none-none-eabi -Xcc -mfloat-abi=soft -Xcc -fshort-enums -Xfrontend -function-sections -enable-experimental-feature Embedded -wmo -parse-as-library ``` ### Additional information _No response_

github.com/swiftlang/swift

Compiler crashes for `mutating subscript` when in Embedded language mode

opened 05:03PM - 18 Nov 24 UTC

colemancda

bug crash triage needed

### Description While developing a Bluetooth LE peripheral for Embedded Swift o…n the Pico W, I came across unexpected compiler behavior. A` mutating subscript` with `private(set)` crashes the compiler at `hasEmbeddedSignature(f)`. I had to change my subscript to a [method](https://github.com/apple/swift-embedded-examples/pull/74/commits/7148f4c4ea86e2275350d620d05792cf3ec3d719). ### Reproduction ```swift struct GATTDatabase { public private(set) subscript(handle handle: UInt16) -> GATTDatabase.Attribute { get { for group in attributeGroups { for attribute in group.attributes { guard attribute.handle != handle else { return attribute } } } fatalError("Invalid handle") } mutating set { for (groupIndex, group) in attributeGroups.enumerated() { for (attributeIndex, attribute) in group.attributes.enumerated() { guard attribute.handle != handle else { attributeGroups[groupIndex].attributes[attributeIndex] = newValue return } } } fatalError("Invalid handle") } } } ``` Crashes the compiler at `hasEmbeddedSignature(f)`, the fix was the move the `mutating set` subscript to a separate method. ```swift struct GATTDatabase { public subscript(handle handle: UInt16) -> GATTDatabase.Attribute { get { guard let attribute = attribute(for: handle) else { fatalError("Invalid handle") } return attribute } } @discardableResult private mutating func setAttribute(_ newValue: Self.Attribute, for handle: UInt16) -> Bool { for (groupIndex, group) in attributeGroups.enumerated() { for (attributeIndex, attribute) in group.attributes.enumerated() { guard attribute.handle != handle else { attributeGroups[groupIndex].attributes[attributeIndex] = newValue return true } } } return false } } ``` ### Stack dump ```text 1. Apple Swift version 6.1-dev (LLVM 9d655fdc6103926, Swift 0d16cbf5d5ef6f9) 2. Compiling with effective version 5.10 3. While evaluating request IRGenRequest(IR Generation for module _swiftcode) Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it): 0 swift-frontend 0x0000000108300e0c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56 1 swift-frontend 0x00000001082ff4f0 llvm::sys::RunSignalHandlers() + 112 2 swift-frontend 0x0000000108301468 SignalHandler(int) + 304 3 libsystem_platform.dylib 0x0000000192a3e584 _sigtramp + 56 4 libsystem_pthread.dylib 0x0000000192a0dc20 pthread_kill + 288 5 libsystem_c.dylib 0x000000019291aa30 abort + 180 6 swift-frontend 0x00000001041d2b60 ASSERT_help() + 0 7 swift-frontend 0x0000000102c23b54 swift::irgen::IRGenerator::addLazyFunction(swift::SILFunction*) + 376 8 swift-frontend 0x0000000102c26660 swift::irgen::IRGenModule::getAddrOfSILFunction(swift::SILFunction*, swift::ForDefinition_t, bool, bool) + 1300 9 swift-frontend 0x0000000102c1fae0 swift::irgen::IRGenModule::getAddrOfLLVMVariableOrGOTEquivalent(swift::irgen::LinkEntity) + 84 10 swift-frontend 0x0000000102c9f264 emitKeyPathComponent(swift::irgen::IRGenModule&, swift::irgen::ConstantStructBuilder&, swift::KeyPathPatternComponent const&, bool, swift::GenericEnvironment*, llvm::ArrayRef<swift::GenericRequirement>, swift::CanType, llvm::ArrayRef<KeyPathIndexOperand>, bool) + 1344 11 swift-frontend 0x0000000102ca31fc swift::irgen::IRGenModule::emitSILProperty(swift::SILProperty*) + 624 12 swift-frontend 0x0000000102c21a28 swift::irgen::IRGenerator::emitGlobalTopLevel(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>> const&) + 992 13 swift-frontend 0x0000000102d3c9c4 swift::IRGenRequest::evaluate(swift::Evaluator&, swift::IRGenDescriptor) const + 2364 14 swift-frontend 0x0000000102d8b848 swift::GeneratedModule swift::SimpleRequest<swift::IRGenRequest, swift::GeneratedModule (swift::IRGenDescriptor), (swift::RequestFlags)17>::callDerived<0ul>(swift::Evaluator&, std::__1::integer_sequence<unsigned long, 0ul>) const + 200 15 swift-frontend 0x0000000102d45120 swift::IRGenRequest::OutputType swift::Evaluator::getResultUncached<swift::IRGenRequest, swift::IRGenRequest::OutputType swift::evaluateOrFatal<swift::IRGenRequest>(swift::Evaluator&, swift::IRGenRequest)::'lambda'()>(swift::IRGenRequest const&, swift::IRGenRequest::OutputType swift::evaluateOrFatal<swift::IRGenRequest>(swift::Evaluator&, swift::IRGenRequest)::'lambda'()) + 212 16 swift-frontend 0x0000000102d3da80 swift::performIRGeneration(swift::ModuleDecl*, swift::IRGenOptions const&, swift::TBDGenOptions const&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>>, llvm::StringRef, swift::PrimarySpecificPaths const&, llvm::ArrayRef<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>, llvm::GlobalVariable**) + 1440 17 swift-frontend 0x00000001028185a4 generateIR(swift::IRGenOptions const&, swift::TBDGenOptions const&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>>, swift::PrimarySpecificPaths const&, llvm::StringRef, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, llvm::GlobalVariable*&, llvm::ArrayRef<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>) + 272 18 swift-frontend 0x0000000102814e54 performCompileStepsPostSILGen(swift::CompilerInstance&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>>, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::PrimarySpecificPaths const&, int&, swift::FrontendObserver*) + 1364 19 swift-frontend 0x00000001028144ec swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1224 20 swift-frontend 0x0000000102820788 withSemanticAnalysis(swift::CompilerInstance&, swift::FrontendObserver*, llvm::function_ref<bool (swift::CompilerInstance&)>, bool) + 160 21 swift-frontend 0x0000000102816180 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 716 22 swift-frontend 0x000000010281584c swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 2328 23 swift-frontend 0x00000001025f125c swift::mainEntry(int, char const**) + 3100 24 dyld 0x0000000192683154 start + 2476 ``` ### Expected behavior The compiler should not crash. ### Environment ``` Apple Swift version 6.1-dev (LLVM 9d655fdc6103926, Swift 0d16cbf5d5ef6f9) Target: arm64-apple-macosx14.0 ``` Targeting the Pico W with the following flags: ``` -target armv6m-none-none-eabi -Xcc -mfloat-abi=soft -Xcc -fshort-enums -Xfrontend -function-sections -enable-experimental-feature Embedded -wmo -parse-as-library ``` ### Additional information _No response_

@rauhul @kubamracek

ColemanCDA · November 26, 2024, 3:12am