Support throwAssertion matcher on SwiftPM on Linux

Author: ikesyo

Sources/Nimble/Matchers/ThrowAssertion.swift

@@ -2,11 +2,89 @@
 import CwlPreconditionTesting
 #elseif canImport(CwlPosixPreconditionTesting)
 import CwlPosixPreconditionTesting
+#elseif canImport(Glibc)
+// swiftlint:disable all
+import Glibc
+
+// This function is called from the signal handler to shut down the thread and return 1 (indicating a SIGILL was received).
+private func callThreadExit() {
+    pthread_exit(UnsafeMutableRawPointer(bitPattern: 1))
+}
+
+// When called, this signal handler simulates a function call to `callThreadExit`
+private func sigIllHandler(code: Int32, info: UnsafeMutablePointer<siginfo_t>?, uap: UnsafeMutableRawPointer?) -> Void {
+    guard let context = uap?.assumingMemoryBound(to: ucontext_t.self) else { return }
+
+    // 1. Decrement the stack pointer
+    context.pointee.uc_mcontext.gregs.15 /* REG_RSP */ -= Int64(MemoryLayout<Int>.size)
+
+    // 2. Save the old Instruction Pointer to the stack.
+    let rsp = context.pointee.uc_mcontext.gregs.15 /* REG_RSP */
+    if let ump = UnsafeMutablePointer<Int64>(bitPattern: Int(rsp)) {
+        ump.pointee = rsp
+    }
+
+    // 3. Set the Instruction Pointer to the new function's address
+    var f: @convention(c) () -> Void = callThreadExit
+    withUnsafePointer(to: &f) {    $0.withMemoryRebound(to: Int64.self, capacity: 1) { ptr in
+        context.pointee.uc_mcontext.gregs.16 /* REG_RIP */ = ptr.pointee
+    } }
+}
+
+/// Without Mach exceptions or the Objective-C runtime, there's nothing to put in the exception object. It's really just a boolean – either a SIGILL was caught or not.
+public class BadInstructionException {
+}
+
+/// Run the provided block. If a POSIX SIGILL is received, handle it and return a BadInstructionException (which is just an empty object in this POSIX signal version). Otherwise return nil.
+/// NOTE: This function is only intended for use in test harnesses – use in a distributed build is almost certainly a bad choice. If a SIGILL is received, the block will be interrupted using a C `longjmp`. The risks associated with abrupt jumps apply here: most Swift functions are *not* interrupt-safe. Memory may be leaked and the program will not necessarily be left in a safe state.
+/// - parameter block: a function without parameters that will be run
+/// - returns: if an SIGILL is raised during the execution of `block` then a BadInstructionException will be returned, otherwise `nil`.
+public func catchBadInstruction(block: @escaping () -> Void) -> BadInstructionException? {
+    // Construct the signal action
+    var sigActionPrev = sigaction()
+    var sigActionNew = sigaction()
+    sigemptyset(&sigActionNew.sa_mask)
+    sigActionNew.sa_flags = SA_SIGINFO
+    sigActionNew.__sigaction_handler = .init(sa_sigaction: sigIllHandler)
+
+    // Install the signal action
+    if sigaction(SIGILL, &sigActionNew, &sigActionPrev) != 0 {
+        fatalError("Sigaction error: \(errno)")
+    }
+
+    defer {
+        // Restore the previous signal action
+        if sigaction(SIGILL, &sigActionPrev, nil) != 0 {
+            fatalError("Sigaction error: \(errno)")
+        }
+    }
+
+    var b = block
+    let caught: Bool = withUnsafeMutablePointer(to: &b) { blockPtr in
+        // Run the block on its own thread
+        var handlerThread: pthread_t = 0
+        let e = pthread_create(&handlerThread, nil, { arg in
+            guard let arg = arg else { return nil }
+            (arg.assumingMemoryBound(to: (() -> Void).self).pointee)()
+            return nil
+        }, blockPtr)
+        precondition(e == 0, "Unable to create thread")
+
+        // Wait for completion and get the result. It will be either `nil` or bitPattern 1
+        var rawResult: UnsafeMutableRawPointer? = nil
+        let e2 = pthread_join(handlerThread, &rawResult)
+        precondition(e2 == 0, "Thread join failed")
+        return Int(bitPattern: rawResult) != 0
+    }
+
+    return caught ? BadInstructionException() : nil
+}
+// swiftlint:enable all
 #endif
 
 public func throwAssertion<Out>() -> Predicate<Out> {
     return Predicate { actualExpression in
-    #if arch(x86_64) && canImport(Darwin)
+    #if arch(x86_64) && (canImport(Darwin) || canImport(Glibc))
         let message = ExpectationMessage.expectedTo("throw an assertion")
 
         var actualError: Error?
@@ -43,9 +121,11 @@ public func throwAssertion<Out>() -> Predicate<Out> {
             return PredicateResult(bool: caughtException != nil, message: message)
         }
     #else
-        fatalError("The throwAssertion Nimble matcher can only run on x86_64 platforms with " +
-            "Objective-C (e.g. macOS, iPhone 5s or later simulators). You can silence this error " +
-            "by placing the test case inside an #if arch(x86_64) or canImport(Darwin) conditional statement")
+        let message = """
+            The throwAssertion Nimble matcher can only run on x86_64 platforms.
+            You can silence this error by placing the test case inside an #if arch(x86_64) conditional statement.
+            """
+        fatalError(message)
     #endif
     }
 }

Tests/NimbleTests/Matchers/ThrowAssertionTest.swift

@@ -6,19 +6,19 @@ private let error: Error = NSError(domain: "test", code: 0, userInfo: nil)
 
 final class ThrowAssertionTest: XCTestCase {
     func testPositiveMatch() {
-        #if canImport(Darwin)
+        #if arch(x86_64)
         expect { () -> Void in fatalError() }.to(throwAssertion())
         #endif
     }
 
     func testErrorThrown() {
-        #if canImport(Darwin)
+        #if arch(x86_64)
         expect { throw error }.toNot(throwAssertion())
         #endif
     }
 
     func testPostAssertionCodeNotRun() {
-        #if canImport(Darwin)
+        #if arch(x86_64)
         var reachedPoint1 = false
         var reachedPoint2 = false
 
@@ -34,7 +34,7 @@ final class ThrowAssertionTest: XCTestCase {
     }
 
     func testNegativeMatch() {
-        #if canImport(Darwin)
+        #if arch(x86_64)
         var reachedPoint1 = false
 
         expect { reachedPoint1 = true }.toNot(throwAssertion())
@@ -44,7 +44,7 @@ final class ThrowAssertionTest: XCTestCase {
     }
 
     func testPositiveMessage() {
-        #if canImport(Darwin)
+        #if arch(x86_64)
         failsWithErrorMessage("expected to throw an assertion") {
             expect { () -> Void? in return }.to(throwAssertion())
         }
@@ -56,21 +56,21 @@ final class ThrowAssertionTest: XCTestCase {
     }
 
     func testNegativeMessage() {
-        #if canImport(Darwin)
+        #if arch(x86_64)
         failsWithErrorMessage("expected to not throw an assertion") {
             expect { () -> Void in fatalError() }.toNot(throwAssertion())
         }
         #endif
     }
 
     func testNonVoidClosure() {
-        #if canImport(Darwin)
+        #if arch(x86_64)
         expect { () -> Int in fatalError() }.to(throwAssertion())
         #endif
     }
 
     func testChainOnThrowAssertion() {
-        #if canImport(Darwin)
+        #if arch(x86_64)
         expect { () -> Int in return 5 }.toNot(throwAssertion()).to(equal(5))
         #endif
     }