Add basic platform support for Android. (#653)

This PR seeks out all the nooks and crannies where we have
platform-specific code or logic and adds Android. In most cases, it's as
simple as changing `os(Linux)` to `os(Linux) || os(Android)` but there
are a few spots where they diverge. The PR should be _mostly_
self-explanatory.

### Checklist:

- [x] Code and documentation should follow the style of the [Style
Guide](https://github.com/apple/swift-testing/blob/main/Documentation/StyleGuide.md).
- [x] If public symbols are renamed or modified, DocC references should
be updated.


Co-authored-by: Saleem Abdulrasool <[email protected]>

Package.swift

@@ -130,7 +130,7 @@ extension Array where Element == PackageDescription.SwiftSetting {
 
       .define("SWT_TARGET_OS_APPLE", .when(platforms: [.macOS, .iOS, .macCatalyst, .watchOS, .tvOS, .visionOS])),
 
-      .define("SWT_NO_EXIT_TESTS", .when(platforms: [.iOS, .watchOS, .tvOS, .visionOS, .wasi])),
+      .define("SWT_NO_EXIT_TESTS", .when(platforms: [.iOS, .watchOS, .tvOS, .visionOS, .wasi, .android])),
       .define("SWT_NO_SNAPSHOT_TYPES", .when(platforms: [.linux, .windows, .wasi])),
       .define("SWT_NO_DYNAMIC_LINKING", .when(platforms: [.wasi])),
     ]

Sources/Testing/ABI/EntryPoints/EntryPoint.swift

@@ -651,7 +651,7 @@ extension Event.ConsoleOutputRecorder.Options {
   /// Whether or not the system terminal claims to support 16-color ANSI escape
   /// codes.
   private static var _terminalSupports16ColorANSIEscapeCodes: Bool {
-#if SWT_TARGET_OS_APPLE || os(Linux)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android)
     if let termVariable = Environment.variable(named: "TERM") {
       return termVariable != "dumb"
     }
@@ -673,7 +673,7 @@ extension Event.ConsoleOutputRecorder.Options {
   /// Whether or not the system terminal claims to support 256-color ANSI escape
   /// codes.
   private static var _terminalSupports256ColorANSIEscapeCodes: Bool {
-#if SWT_TARGET_OS_APPLE || os(Linux)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android)
     if let termVariable = Environment.variable(named: "TERM") {
       return strstr(termVariable, "256") != nil
     }
@@ -695,7 +695,7 @@ extension Event.ConsoleOutputRecorder.Options {
   /// Whether or not the system terminal claims to support true-color ANSI
   /// escape codes.
   private static var _terminalSupportsTrueColorANSIEscapeCodes: Bool {
-#if SWT_TARGET_OS_APPLE || os(Linux)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android)
     if let colortermVariable = Environment.variable(named: "COLORTERM") {
       return strstr(colortermVariable, "truecolor") != nil
     }

Sources/Testing/ABI/EntryPoints/SwiftPMEntryPoint.swift

@@ -24,7 +24,7 @@ private import _TestingInternals
 ///
 /// This constant is not part of the public interface of the testing library.
 var EXIT_NO_TESTS_FOUND: CInt {
-#if SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || os(WASI)
   EX_UNAVAILABLE
 #elseif os(Windows)
   CInt(ERROR_NOT_FOUND)

Sources/Testing/Events/Recorder/Event.Symbol.swift

@@ -100,7 +100,7 @@ extension Event.Symbol {
   /// be used to represent it in text-based output. The value of this property
   /// is platform-dependent.
   public var unicodeCharacter: Character {
-#if SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || os(WASI)
     switch self {
     case .default:
       // Unicode: WHITE DIAMOND

Sources/Testing/SourceAttribution/Backtrace.swift

@@ -71,6 +71,10 @@ public struct Backtrace: Sendable {
         }
 #elseif os(Linux)
         initializedCount = .init(backtrace(addresses.baseAddress!, .init(addresses.count)))
+#elseif os(Android)
+        addresses.withMemoryRebound(to: UnsafeMutableRawPointer.self) { addresses in
+          initializedCount = .init(backtrace(addresses.baseAddress!, .init(addresses.count)))
+        }
 #elseif os(Windows)
         initializedCount = Int(RtlCaptureStackBackTrace(0, ULONG(addresses.count), addresses.baseAddress!, nil))
 #elseif os(WASI)

Sources/Testing/Support/Additions/CommandLineAdditions.swift

@@ -29,9 +29,9 @@ extension CommandLine {
         }
       }
       return result!
-#elseif os(Linux)
+#elseif os(Linux) || os(Android)
       return try withUnsafeTemporaryAllocation(of: CChar.self, capacity: Int(PATH_MAX) * 2) { buffer in
-        let readCount = readlink("/proc/\(getpid())/exe", buffer.baseAddress!, buffer.count - 1)
+        let readCount = readlink("/proc/self/exe", buffer.baseAddress!, buffer.count - 1)
         guard readCount >= 0 else {
           throw CError(rawValue: swt_errno())
         }

Sources/Testing/Support/Environment.swift

@@ -42,7 +42,7 @@ enum Environment {
     }
   }
 
-#if SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || os(WASI)
   /// Get all environment variables from a POSIX environment block.
   ///
   /// - Parameters:
@@ -103,7 +103,7 @@ enum Environment {
     }
 #endif
     return _get(fromEnviron: _NSGetEnviron()!.pointee!)
-#elseif os(Linux)
+#elseif os(Linux) || os(Android)
     _get(fromEnviron: swt_environ())
 #elseif os(WASI)
     _get(fromEnviron: __wasilibc_get_environ())
@@ -170,7 +170,7 @@ enum Environment {
       }
       return nil
     }
-#elseif SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
+#elseif SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || os(WASI)
     getenv(name).flatMap { String(validatingCString: $0) }
 #elseif os(Windows)
     name.withCString(encodedAs: UTF16.self) { name in

Sources/Testing/Support/FileHandle.swift

@@ -156,7 +156,7 @@ struct FileHandle: ~Copyable, Sendable {
   /// descriptor, `nil` is passed to `body`.
   borrowing func withUnsafePOSIXFileDescriptor<R>(_ body: (CInt?) throws -> R) rethrows -> R {
     try withUnsafeCFILEHandle { handle in
-#if SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || os(WASI)
       let fd = fileno(handle)
 #elseif os(Windows)
       let fd = _fileno(handle)
@@ -215,7 +215,7 @@ struct FileHandle: ~Copyable, Sendable {
   /// other threads.
   borrowing func withLock<R>(_ body: () throws -> R) rethrows -> R {
     try withUnsafeCFILEHandle { handle in
-#if SWT_TARGET_OS_APPLE || os(Linux)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android)
       flockfile(handle)
       defer {
         funlockfile(handle)
@@ -250,7 +250,7 @@ extension FileHandle {
     // If possible, reserve enough space in the resulting buffer to contain
     // the contents of the file being read.
     var size: Int?
-#if SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || os(WASI)
     withUnsafePOSIXFileDescriptor { fd in
       var s = stat()
       if let fd, 0 == fstat(fd, &s) {
@@ -388,7 +388,7 @@ extension FileHandle {
 extension FileHandle {
   /// Is this file handle a TTY or PTY?
   var isTTY: Bool {
-#if SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || os(WASI)
     // If stderr is a TTY and TERM is set, that's good enough for us.
     withUnsafePOSIXFileDescriptor { fd in
       if let fd, 0 != isatty(fd), let term = Environment.variable(named: "TERM"), !term.isEmpty {
@@ -414,7 +414,7 @@ extension FileHandle {
 
   /// Is this file handle a pipe or FIFO?
   var isPipe: Bool {
-#if SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || os(WASI)
     withUnsafePOSIXFileDescriptor { fd in
       guard let fd else {
         return false

Sources/Testing/Support/GetSymbol.swift

@@ -13,7 +13,7 @@ internal import _TestingInternals
 #if !SWT_NO_DYNAMIC_LINKING
 
 /// The platform-specific type of a loaded image handle.
-#if SWT_TARGET_OS_APPLE || os(Linux)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android)
 typealias ImageAddress = UnsafeMutableRawPointer
 #elseif os(Windows)
 typealias ImageAddress = HMODULE
@@ -30,7 +30,9 @@ typealias ImageAddress = Never
 /// declare a wrapper function in the internal module's Stubs.h file.
 #if SWT_TARGET_OS_APPLE
 private nonisolated(unsafe) let RTLD_DEFAULT = ImageAddress(bitPattern: -2)
-#elseif os(Linux)
+#elseif os(Android) && _pointerBitWidth(_32)
+private nonisolated(unsafe) let RTLD_DEFAULT = ImageAddress(bitPattern: 0xFFFFFFFF)
+#elseif os(Linux) || os(Android)
 private nonisolated(unsafe) let RTLD_DEFAULT = ImageAddress(bitPattern: 0)
 #endif
 
@@ -57,7 +59,7 @@ private nonisolated(unsafe) let RTLD_DEFAULT = ImageAddress(bitPattern: 0)
 /// calling `EnumProcessModules()` and iterating over the returned handles
 /// looking for one containing the given function.
 func symbol(in handle: ImageAddress? = nil, named symbolName: String) -> UnsafeRawPointer? {
-#if SWT_TARGET_OS_APPLE || os(Linux)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android)
   dlsym(handle ?? RTLD_DEFAULT, symbolName).map(UnsafeRawPointer.init)
 #elseif os(Windows)
   symbolName.withCString { symbolName in

Sources/Testing/Support/Locked.swift

@@ -36,7 +36,7 @@ struct Locked<T>: RawRepresentable, Sendable where T: Sendable {
   /// To keep the implementation of this type as simple as possible,
   /// `pthread_mutex_t` is used on Apple platforms instead of `os_unfair_lock`
   /// or `OSAllocatedUnfairLock`.
-#if SWT_TARGET_OS_APPLE || os(Linux) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
   private typealias _Lock = pthread_mutex_t
 #elseif os(Windows)
   private typealias _Lock = SRWLOCK
@@ -52,7 +52,7 @@ struct Locked<T>: RawRepresentable, Sendable where T: Sendable {
   private final class _Storage: ManagedBuffer<T, _Lock> {
     deinit {
       withUnsafeMutablePointerToElements { lock in
-#if SWT_TARGET_OS_APPLE || os(Linux) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
         _ = pthread_mutex_destroy(lock)
 #elseif os(Windows)
         // No deinitialization needed.
@@ -71,7 +71,7 @@ struct Locked<T>: RawRepresentable, Sendable where T: Sendable {
   init(rawValue: T) {
     _storage = _Storage.create(minimumCapacity: 1, makingHeaderWith: { _ in rawValue })
     _storage.withUnsafeMutablePointerToElements { lock in
-#if SWT_TARGET_OS_APPLE || os(Linux) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
       _ = pthread_mutex_init(lock, nil)
 #elseif os(Windows)
       InitializeSRWLock(lock)
@@ -101,7 +101,7 @@ struct Locked<T>: RawRepresentable, Sendable where T: Sendable {
   /// concurrency tools.
   nonmutating func withLock<R>(_ body: (inout T) throws -> R) rethrows -> R {
     try _storage.withUnsafeMutablePointers { rawValue, lock in
-#if SWT_TARGET_OS_APPLE || os(Linux) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
       _ = pthread_mutex_lock(lock)
       defer {
         _ = pthread_mutex_unlock(lock)
@@ -121,7 +121,7 @@ struct Locked<T>: RawRepresentable, Sendable where T: Sendable {
     }
   }
 
-#if SWT_TARGET_OS_APPLE || os(Linux) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || (os(WASI) && compiler(>=6.1) && _runtime(_multithreaded))
   /// Acquire the lock and invoke a function while it is held, yielding both the
   /// protected value and a reference to the lock itself.
   ///

Sources/Testing/Support/Versions.swift

@@ -55,6 +55,10 @@ let operatingSystemVersion: String = {
       return "\(release) (\(version))"
     }
   }
+#elseif os(Android)
+  if let version = systemProperty(named: "ro.build.version.release") {
+    return "Android \(version)"
+  }
 #elseif os(Windows)
   // See if we can query the kernel directly, bypassing the fake-out logic added
   // in Windows 10 and later that misreports the OS version. GetVersionExW()
@@ -170,3 +174,22 @@ func sysctlbyname(_ name: String, as _: String.Type) -> String? {
   }
 }
 #endif
+
+#if os(Android)
+/// Get the Android system property with the given name.
+///
+/// - Parameters:
+///   - name: The name of the system property to get.
+///
+/// - Returns: The value of the requested system property, or `nil` if it could
+///   not be read or could not be converted to a string.
+func systemProperty(named name: String) -> String? {
+  withUnsafeTemporaryAllocation(of: CChar.self, capacity: Int(PROP_VALUE_MAX)) { buffer in
+    let length = __system_property_get(name, buffer.baseAddress!)
+    if length > 0 {
+      return String(validatingCString: buffer.baseAddress!)
+    }
+    return nil
+  }
+}
+#endif

Sources/Testing/Traits/Tags/Tag.Color+Loading.swift

@@ -61,10 +61,11 @@ var swiftTestingDirectoryPath: String? {
   if let homeDirectoryPath = _homeDirectoryPath {
     return appendPathComponent(swiftTestingDirectoryName, to: homeDirectoryPath)
   }
-#elseif SWT_TARGET_OS_APPLE
+#elseif SWT_TARGET_OS_APPLE || os(Android)
   // Other Apple/Darwin platforms do not support the concept of a home
   // directory. One exists for the current user, but it's not something that
   // actually contains user-configurable data like a .swift-testing directory.
+  // Android also does not support per-user home directories (does it?)
 #elseif os(Windows)
   if let appDataDirectoryPath = _appDataDirectoryPath {
     return appendPathComponent(swiftTestingDirectoryName, to: appDataDirectoryPath)

Sources/_TestingInternals/Discovery.cpp

@@ -306,7 +306,7 @@ static void enumerateTypeMetadataSections(const SectionEnumerator& body) {
   }
 }
 
-#elif defined(__linux__) || defined(_WIN32) || defined(__wasi__)
+#elif defined(__linux__) || defined(_WIN32) || defined(__wasi__) || defined(__ANDROID__)
 #pragma mark - Linux/Windows implementation
 
 /// Specifies the address range corresponding to a section.

Sources/_TestingInternals/include/Includes.h

@@ -120,4 +120,9 @@
 #include <Psapi.h>
 #endif
 
+#if defined(__ANDROID__)
+#pragma clang module import posix_filesystem.linux_stat
+#include <sys/system_properties.h>
+#endif
+
 #endif

Sources/_TestingInternals/include/Stubs.h

@@ -74,7 +74,7 @@ static LANGID swt_MAKELANGID(int p, int s) {
 }
 #endif
 
-#if defined(__linux__)
+#if defined(__linux__) || defined(__ANDROID__)
 /// The environment block.
 ///
 /// By POSIX convention, the environment block variable is declared in client
@@ -97,6 +97,7 @@ static char *_Nullable *_Null_unspecified swt_environ(void) {
 SWT_IMPORT_FROM_STDLIB int pthread_setname_np(pthread_t, const char *);
 #endif
 
+#if !defined(__ANDROID__)
 #if __has_include(<signal.h>) && defined(si_pid)
 /// Get the value of the `si_pid` field of a `siginfo_t` structure.
 ///
@@ -120,6 +121,7 @@ static int swt_siginfo_t_si_status(const siginfo_t *siginfo) {
   return siginfo->si_status;
 }
 #endif
+#endif
 
 #if defined(__wasi__)
 /// Get the version of the C standard library and runtime used by WASI, if

Tests/TestingTests/ABIEntryPointTests.swift

@@ -127,7 +127,7 @@ struct ABIEntryPointTests {
     passing arguments: __CommandLineArguments_v0,
     recordHandler: @escaping @Sendable (_ recordJSON: UnsafeRawBufferPointer) -> Void = { _ in }
   ) async throws -> Bool {
-#if !os(Linux) && !SWT_NO_DYNAMIC_LINKING
+#if !os(Linux) && !os(Android) && !SWT_NO_DYNAMIC_LINKING
     // Get the ABI entry point by dynamically looking it up at runtime.
     //
     // NOTE: The standard Linux linker does not allow exporting symbols from

Tests/TestingTests/Support/EnvironmentTests.swift

@@ -90,7 +90,7 @@ extension Environment {
       environment[name] = value
     }
     return true
-#elseif SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
+#elseif SWT_TARGET_OS_APPLE || os(Linux) || os(Android) || os(WASI)
     if let value {
       return 0 == setenv(name, value, 1)
     }

Tests/TestingTests/Support/FileHandleTests.swift

@@ -14,7 +14,7 @@ private import _TestingInternals
 #if !SWT_NO_FILE_IO
 // NOTE: we don't run these tests on iOS (etc.) because processes on those
 // platforms are sandboxed and do not have arbitrary filesystem access.
-#if os(macOS) || os(Linux) || os(Windows)
+#if os(macOS) || os(Linux) || os(Android) || os(Windows)
 @Suite("FileHandle Tests")
 struct FileHandleTests {
   // FileHandle is non-copyable, so it cannot yet be used as a test parameter.
@@ -226,6 +226,8 @@ func temporaryDirectory() throws -> String {
   }
 #elseif os(Linux)
   "/tmp"
+#elseif os(Android)
+  Environment.variable(named: "TMPDIR") ?? "/data/local/tmp"
 #elseif os(Windows)
   try withUnsafeTemporaryAllocation(of: wchar_t.self, capacity: Int(MAX_PATH + 1)) { buffer in
     // NOTE: GetTempPath2W() was introduced in Windows 10 Build 20348.

cmake/modules/shared/CompilerSettings.cmake

@@ -20,7 +20,7 @@ add_compile_options(
 if(APPLE)
   add_compile_definitions("SWT_TARGET_OS_APPLE")
 endif()
-set(SWT_NO_EXIT_TESTS_LIST "iOS" "watchOS" "tvOS" "visionOS" "WASI")
+set(SWT_NO_EXIT_TESTS_LIST "iOS" "watchOS" "tvOS" "visionOS" "WASI" "Android")
 if(CMAKE_SYSTEM_NAME IN_LIST SWT_NO_EXIT_TESTS_LIST)
   add_compile_definitions("SWT_NO_EXIT_TESTS")
 endif()