trap SIGSEGV, SIGBUS and SIGFPE by default, in addition to SIGILL (#58)

motivation: print crash trace on segmentation faults and other common failures beyond illegal instructions

changes:
* include SIGSEGV, SIGBUS and SIGFPE in the default signals trapped
* update and improve tests

.gitignore

@@ -3,3 +3,4 @@
 /Packages
 /*.xcodeproj
 .swiftpm
+.*.sw[nop]

.swiftformat

@@ -8,7 +8,6 @@
 --self insert
 --patternlet inline
 --stripunusedargs unnamed-only
---comments ignore
 --ifdef no-indent
 
 # rules

.travis.yml

@@ -1,50 +0,0 @@
-branches:
-  only:
-    - master
-
-# The matrix of builds should cover each combination of Swift version
-# and platform that is supported. The version of Swift used is specified
-# by .swift-version, unless SWIFT_SNAPSHOT is specified.
-matrix:
-  include:
-    - os: linux
-      dist: xenial
-      sudo: required
-      services: docker
-      env: DOCKER_IMAGE=swift:4.2.4 SWIFT_SNAPSHOT=4.2.4
-    - os: linux
-      dist: xenial
-      sudo: required
-      services: docker
-      env: DOCKER_IMAGE=swift:5.0-xenial
-    - os: linux
-      dist: xenial
-      sudo: required
-      services: docker
-      env: DOCKER_IMAGE=swift:5.0-bionic
-    - os: linux
-      dist: xenial
-      sudo: required
-      services: docker
-      env: DOCKER_IMAGE=swift:5.1-xenial
-    - os: linux
-      dist: xenial
-      sudo: required
-      services: docker
-      env: DOCKER_IMAGE=swift:5.1-bionic
-    - os: osx
-      osx_image: xcode10.1
-      sudo: required
-      env: SWIFT_SNAPSHOT=4.2.1
-    - os: osx
-      osx_image: xcode10.3
-      sudo: required
-    - os: osx
-      osx_image: xcode11.2
-      sudo: required
-
-before_install:
-  - git clone https://github.com/IBM-Swift/Package-Builder.git
-
-script:
-  - ./Package-Builder/build-package.sh -projectDir $TRAVIS_BUILD_DIR

README.md

@@ -2,8 +2,14 @@
 
 This Swift package provides support for automatically printing crash backtraces of Swift programs.
 
+The library is designed to fill a gap in backtraces support for Swift on non-Darwin platforms. 
+When this gap is closed at the language runtime level, this library will become redundant and be deprecated.
+
 ## Usage
 
+When building web-services and daemons, direct usage of this library is discouraged. 
+Instead, use [swift-service-lifecycle](https://github.com/swift-server/swift-service-lifecycle) which helps manage the application lifecycle including setting up backtraces hooks when needed. 
+
 Add `https://github.com/swift-server/swift-backtrace.git` as a dependency in your `Package.swift`.
 
 ### Crash backtraces
@@ -17,7 +23,7 @@ import Backtrace
 Backtrace.install()
 ```
 
-Finally, make sure you build your application with debug symbols enabled:
+Finally, for Swift < 5.2, make sure you build your application with debug symbols enabled. Debug symbols are automatically included for Swift 5.2 and above.
 
 ```
 $ swift build -c release -Xswiftc -g
@@ -25,9 +31,14 @@ $ swift build -c release -Xswiftc -g
 
 When your app crashes, a stacktrace will be printed to `stderr`.
 
+## Security
+
+Please see [SECURITY.md](SECURITY.md) for details on the security process.
 
 ## Acknowledgements
 
 Ian Partridge ([GitHub](https://github.com/ianpartridge/), [Twitter](https://twitter.com/alfa)) the original author of this package.
 
 Johannes Weiss ([GitHub](https://github.com/weissi), [Twitter](https://twitter.com/johannesweiss)) for the signal handling code.
+
+Saleem Abdulrasool ([GitHub](https://github.com/compnerd), [Twitter](https://twitter.com/compnerd)) for the Windows port.

SECURITY.md

@@ -0,0 +1,43 @@
+# Security
+
+This document specifies the security process for the Backtrace project.
+
+## Disclosures
+
+### Private Disclosure Process
+
+The Backtrace maintainers ask that known and suspected vulnerabilities be
+privately and responsibly disclosed by emailing
+[sswg-security-reports@forums.swift.org](mailto:sswg-security-reports@forums.swift.org)
+with the all the required detail.
+**Do not file a public issue.**
+
+#### When to report a vulnerability
+
+* You think you have discovered a potential security vulnerability in Backtrace.
+* You are unsure how a vulnerability affects Backtrace.
+
+#### What happens next?
+
+* A member of the team will acknowledge receipt of the report within 3
+  working days (United States). This may include a request for additional
+  information about reproducing the vulnerability.
+* We will privately inform the Swift Server Work Group ([SSWG][sswg]) of the
+  vulnerability within 10 days of the report as per their [security
+  guidelines][sswg-security].
+* Once we have identified a fix we may ask you to validate it. We aim to do this
+  within 30 days. In some cases this may not be possible, for example when the
+  vulnerability exists at the protocol level and the industry must coordinate on
+  the disclosure process.
+* If a CVE number is required, one will be requested from [MITRE][mitre]
+  providing you with full credit for the discovery.
+* We will decide on a planned release date and let you know when it is.
+* Prior to release, we will inform major dependents that a security-related
+  patch is impending.
+* Once the fix has been released we will publish a security advisory on GitHub
+  and in the Server → Security Updates category on the [Swift forums][swift-forums-sec].
+
+[sswg]: https://github.com/swift-server/sswg
+[sswg-security]: https://github.com/swift-server/sswg/blob/main/security/README.md
+[swift-forums-sec]: https://forums.swift.org/c/server/security-updates/
+[mitre]: https://cveform.mitre.org/

Sources/Backtrace/Backtrace.swift

@@ -21,7 +21,7 @@ typealias CBacktraceFullCallback = @convention(c) (_ data: UnsafeMutableRawPoint
 typealias CBacktraceSimpleCallback = @convention(c) (_ data: UnsafeMutableRawPointer?, _ pc: UInt) -> CInt
 typealias CBacktraceSyminfoCallback = @convention(c) (_ data: UnsafeMutableRawPointer?, _ pc: UInt, _ filename: UnsafePointer<CChar>?, _ symval: UInt, _ symsize: UInt) -> Void
 
-private let state = backtrace_create_state(CommandLine.arguments[0], /* BACKTRACE_SUPPORTS_THREADS */ 1, nil, nil)
+private let state = backtrace_create_state(nil, /* BACKTRACE_SUPPORTS_THREADS */ 1, nil, nil)
 
 private let fullCallback: CBacktraceFullCallback? = {
     _, pc, filename, lineno, function in
@@ -53,18 +53,32 @@ private let fullCallback: CBacktraceFullCallback? = {
 }
 
 private let errorCallback: CBacktraceErrorCallback? = {
-    _, msg, _ in
+    _, msg, errNo in
     if let msg = msg {
-        _ = withVaList([msg]) { vaList in
-            vfprintf(stderr, "%s\n", vaList)
+        _ = withVaList([msg, errNo]) { vaList in
+            vfprintf(stderr, "SwiftBacktrace ERROR: %s (errno: %d)\n", vaList)
         }
     }
 }
 
+private func printBacktrace(signal: CInt) {
+    _ = fputs("Received signal \(signal). Backtrace:\n", stderr)
+    backtrace_full(state, /* skip */ 0, fullCallback, errorCallback, nil)
+}
+
 public enum Backtrace {
+    /// Install the backtrace handler on default signals: `SIGILL`, `SIGSEGV`, `SIGBUS`, `SIGFPE`.
     public static func install() {
-        self.setupHandler(signal: SIGILL) { _ in
-            backtrace_full(state, /* skip */ 0, fullCallback, errorCallback, nil)
+        Backtrace.install(signals: [SIGILL, SIGSEGV, SIGBUS, SIGFPE])
+    }
+
+    /// Install the backtrace handler when any of `signals` happen.
+    public static func install(signals: [CInt]) {
+        for signal in signals {
+            self.setupHandler(signal: signal) { signal in
+                printBacktrace(signal: signal)
+                raise(signal)
+            }
         }
     }
 
@@ -86,10 +100,173 @@ public enum Backtrace {
     }
 }
 
+#elseif os(Windows)
+#if swift(<5.4)
+#error("unsupported Swift version")
+#else
+@_implementationOnly import CRT
+@_implementationOnly import WinSDK
+#endif
+
+public enum Backtrace {
+    private static var MachineType: DWORD {
+        #if arch(arm)
+        DWORD(IMAGE_FILE_MACHINE_ARMNT)
+        #elseif arch(arm64)
+        DWORD(IMAGE_FILE_MACHINE_ARM64)
+        #elseif arch(i386)
+        DWORD(IMAGE_FILE_MACHINE_I386)
+        #elseif arch(x86_64)
+        DWORD(IMAGE_FILE_MACHINE_AMD64)
+        #else
+        #error("unsupported architecture")
+        #endif
+    }
+
+    @available(*, deprecated, message: "signal selection unavailable on Windows")
+    public static func install(signals: [CInt]) {
+        Backtrace.install()
+    }
+
+    public static func install() {
+        // Install a last-chance vectored exception handler to capture the error
+        // before the termination and report the stack trace.  It is unlikely
+        // that this will be recovered at this point by a SEH handler.
+        _ = AddVectoredExceptionHandler(0) { _ in
+            // NOTE: GetCurrentProcess does not increment the reference count on
+            // the process.  This handle should _not_ be closed upon completion.
+            let hProcess: HANDLE = GetCurrentProcess()
+
+            var cxr: CONTEXT = CONTEXT()
+            cxr.ContextFlags =
+                DWORD(CONTEXT_CONTROL | CONTEXT_INTEGER | CONTEXT_FLOATING_POINT)
+            RtlCaptureContext(&cxr)
+
+            _ = SymInitializeW(hProcess, nil, true)
+            _ = SymSetOptions(DWORD(SYMOPT_DEFERRED_LOADS | SYMOPT_LOAD_LINES | SYMOPT_UNDNAME))
+
+            var Frame: STACKFRAME64 = STACKFRAME64()
+            #if arch(arm)
+            Frame.AddrPC.Offset = cxr.Pc
+            Frame.AddrFrame.Offset = cxr.R11
+            Frame.AddrStack.Offset = cxr.Sp
+            #elseif arch(arm64)
+            Frame.AddrPC.Offset = cxr.Pc
+            Frame.AddrFrame.Offset = cxr.Fp
+            Frame.AddrStack.Offset = cxr.Sp
+            #elseif arch(i386)
+            Frame.AddrPC.Offset = cxr.Eip
+            Frame.AddrFrame.Offset = cxr.Ebp
+            Frame.AddrStack.Offset = cxr.Esp
+            #elseif arch(x86_64)
+            Frame.AddrPC.Offset = cxr.Rip
+            Frame.AddrFrame.Offset = cxr.Rbp
+            Frame.AddrStack.Offset = cxr.Rsp
+            #else
+            #error("unsupported architecture")
+            #endif
+            Frame.AddrPC.Mode = AddrModeFlat
+            Frame.AddrFrame.Mode = AddrModeFlat
+            Frame.AddrStack.Mode = AddrModeFlat
+
+            // Constant indicating the maximum symbol length that we expect
+            // during symbolication of the stack trace.
+            let kMaxSymbolLength: Int = 255
+
+            // Heap allocate the buffer as we need to account for the trailing
+            // storage that we need to provide.
+            let pSymbolBuffer: UnsafeMutableRawPointer =
+                UnsafeMutableRawPointer.allocate(byteCount: MemoryLayout<IMAGEHLP_SYMBOL64>.size + kMaxSymbolLength,
+                                                 alignment: 1)
+            defer { pSymbolBuffer.deallocate() }
+
+            let pSymbol: UnsafeMutablePointer<IMAGEHLP_SYMBOL64> =
+                pSymbolBuffer.bindMemory(to: IMAGEHLP_SYMBOL64.self,
+                                         capacity: 1)
+
+            let hThread: HANDLE = GetCurrentThread()
+            while StackWalk64(Backtrace.MachineType, hProcess, hThread,
+                              &Frame, &cxr, nil, SymFunctionTableAccess64,
+                              SymGetModuleBase64, nil) {
+                var qwModuleBase: DWORD64 =
+                    SymGetModuleBase64(hProcess, Frame.AddrPC.Offset)
+
+                let module: String = withUnsafeMutablePointer(to: &qwModuleBase) {
+                    $0.withMemoryRebound(to: HINSTANCE.self, capacity: 1) { hInstance in
+                        String(decoding: [WCHAR](unsafeUninitializedCapacity: Int(MAX_PATH + 1)) {
+                            $1 = Int(GetModuleFileNameW(hInstance.pointee,
+                                                        $0.baseAddress,
+                                                        DWORD($0.count)))
+                        }, as: UTF16.self)
+                    }
+                }
+
+                pSymbol.pointee.SizeOfStruct =
+                    DWORD(MemoryLayout<IMAGEHLP_SYMBOL64>.size)
+                pSymbol.pointee.MaxNameLength = DWORD(kMaxSymbolLength)
+                _ = SymGetSymFromAddr64(hProcess, Frame.AddrPC.Offset, nil,
+                                        pSymbol)
+
+                var symbol: String =
+                    withUnsafePointer(to: &pSymbol.pointee.Name) {
+                        String(cString: $0)
+                    }
+
+                // Undecorate Swift 3+ names only.  Earlier Swift decorations
+                // are unsupported.  Any MSVC name decoration has been
+                // unperformed during the DbgHelp operation through the use of
+                // the `SYMOPT_UNDNAME` option.
+                if symbol.hasPrefix("$s") || symbol.hasPrefix("$S") {
+                    symbol = _stdlib_demangleName(symbol)
+                }
+
+                var Displacement: DWORD = 0
+                var Line: IMAGEHLP_LINE64 = IMAGEHLP_LINE64()
+                Line.SizeOfStruct = DWORD(MemoryLayout<IMAGEHLP_LINE64>.size)
+                _ = SymGetLineFromAddr64(hProcess, Frame.AddrPC.Offset,
+                                         &Displacement, &Line)
+
+                var details: String = ""
+
+                if !symbol.isEmpty {
+                    // Truncate the module path to the filename.  The
+                    // `PathFindFileNameW` call will return the beginning of the
+                    // string if a path separator character is not found.
+                    if let pszModule = module.withCString(encodedAs: UTF16.self,
+                                                          PathFindFileNameW) {
+                        details.append(", \(String(decodingCString: pszModule, as: UTF16.self))!\(symbol)")
+                    }
+                }
+
+                if let szFileName = Line.FileName {
+                    details.append(" at \(String(cString: szFileName)):\(Line.LineNumber)")
+                }
+
+                _ = details.withCString { pszDetails in
+                    withVaList([Frame.AddrPC.Offset, pszDetails]) {
+                        #if arch(arm64) || arch(x86_64)
+                        vfprintf(stderr, "%#016x%s\n", $0)
+                        #else
+                        vfprintf(stderr, "%#08x%s\n", $0)
+                        #endif
+                    }
+                }
+            }
+
+            _ = SymCleanup(hProcess)
+
+            // We have not handled the exception, continue the search.
+            return EXCEPTION_CONTINUE_SEARCH
+        }
+    }
+}
+
 #else
 public enum Backtrace {
     public static func install() {}
 
+    public static func install(signals: [CInt]) {}
+
     @available(*, deprecated, message: "This method will be removed in the next major version.")
     public static func print() {}
 }

Sources/Backtrace/Demangle.swift

@@ -14,7 +14,16 @@
 
 #if os(Linux)
 import Glibc
+#elseif os(Windows)
+#if swift(<5.4)
+#error("unsupported Swift version")
+#else
+@_implementationOnly
+import ucrt
+#endif
+#endif
 
+#if os(Linux) || os(Windows)
 @_silgen_name("swift_demangle")
 public
 func _stdlib_demangleImpl(

Sources/CBacktrace/fileline.c

@@ -94,14 +94,14 @@ fileline_initialize (struct backtrace_state *state,
 	  filename = state->filename;
 	  break;
 	case 1:
-	  filename = getexecname ();
-	  break;
-	case 2:
 	  filename = "/proc/self/exe";
 	  break;
-	case 3:
+	case 2:
 	  filename = "/proc/curproc/file";
 	  break;
+	case 3:
+	  filename = getexecname ();
+	  break;
 	case 4:
 	  snprintf (buf, sizeof (buf), "/proc/%ld/object/a.out",
 		    (long) getpid ());

Sources/CBacktrace/mmap.c

@@ -170,7 +170,7 @@ backtrace_alloc (struct backtrace_state *state,
       if (page == MAP_FAILED)
 	{
 	  if (error_callback)
-	    error_callback (data, "mmap", errno);
+	    error_callback (data, "mmap for alloc", errno);
 	}
       else
 	{

Sources/CBacktrace/mmapio.c

@@ -71,7 +71,7 @@ backtrace_get_view (struct backtrace_state *state ATTRIBUTE_UNUSED,
   map = mmap (NULL, size, PROT_READ, MAP_PRIVATE, descriptor, pageoff);
   if (map == MAP_FAILED)
     {
-      error_callback (data, "mmap", errno);
+      error_callback (data, "mmap file i/o", errno);
       return 0;
     }
 

Sources/Sample/main.swift

@@ -13,7 +13,28 @@
 //===----------------------------------------------------------------------===//
 
 import Backtrace
+#if canImport(Darwin)
+import Darwin
+#elseif os(Linux)
+import Glibc
+#endif
+
+Backtrace.install()
+
+func raiseSignal(_ signal: Int32) {
+    raise(signal)
+}
 
 let reason = CommandLine.arguments.count == 2 ? CommandLine.arguments[1] : "unknown"
-Backtrace.install()
-fatalError(reason)
+switch reason.uppercased() {
+case "SIGILL":
+    raiseSignal(SIGILL)
+case "SIGSEGV":
+    raiseSignal(SIGSEGV)
+case "SIGBUS":
+    raiseSignal(SIGBUS)
+case "SIGFPE":
+    raiseSignal(SIGFPE)
+default:
+    fatalError(reason)
+}

Tests/BacktraceTests/BacktraceTests+XCTest.swift

@@ -25,7 +25,11 @@ import XCTest
 extension BacktraceTests {
     public static var allTests: [(String, (BacktraceTests) -> () throws -> Void)] {
         return [
-            ("testBacktrace", testBacktrace),
+            ("testFatalError", testFatalError),
+            ("testSIGILL", testSIGILL),
+            ("testSIGSEGV", testSIGSEGV),
+            ("testSIGBUS", testSIGBUS),
+            ("testSIGFPE", testSIGFPE),
         ]
     }
 }

Tests/BacktraceTests/BacktraceTests.swift

@@ -15,22 +15,76 @@
 import XCTest
 
 public final class BacktraceTests: XCTestCase {
-    func testBacktrace() {
-        #if os(Linux)
+    func testFatalError() throws {
+        #if !os(Linux)
+        try XCTSkipIf(true, "test is only supported on Linux")
+        #endif
+
         let expectedError = UUID().uuidString
+        let stderr = try runSample(reason: expectedError)
+        print(stderr)
+
+        XCTAssert(stderr.contains("Received signal 4. Backtrace:"))
+        XCTAssert(stderr.contains("Current stack trace:"), "expected stanard error to include backtrace")
+        XCTAssert(stderr.contains("Fatal error: \(expectedError)"), "expected stanard error to include error information")
+    }
+
+    func testSIGILL() throws {
+        #if !os(Linux)
+        try XCTSkipIf(true, "test is only supported on Linux")
+        #endif
+
+        let stderr = try runSample(reason: "SIGILL")
+        print(stderr)
+
+        XCTAssert(stderr.contains("Received signal \(SIGILL). Backtrace:"))
+        XCTAssert(stderr.contains("Sample.raiseSignal"))
+    }
+
+    func testSIGSEGV() throws {
+        #if !os(Linux)
+        try XCTSkipIf(true, "test is only supported on Linux")
+        #endif
+
+        let stderr = try runSample(reason: "SIGSEGV")
+        print(stderr)
+
+        XCTAssert(stderr.contains("Received signal \(SIGSEGV). Backtrace:"))
+        XCTAssert(stderr.contains("Sample.raiseSignal"))
+    }
+
+    func testSIGBUS() throws {
+        #if !os(Linux)
+        try XCTSkipIf(true, "test is only supported on Linux")
+        #endif
+
+        let stderr = try runSample(reason: "SIGBUS")
+        print(stderr)
+
+        XCTAssert(stderr.contains("Received signal \(SIGBUS). Backtrace:"))
+        XCTAssert(stderr.contains("Sample.raiseSignal"))
+    }
+
+    func testSIGFPE() throws {
+        #if !os(Linux)
+        try XCTSkipIf(true, "test is only supported on Linux")
+        #endif
+
+        let stderr = try runSample(reason: "SIGFPE")
+        print(stderr)
+
+        XCTAssert(stderr.contains("Received signal \(SIGFPE). Backtrace:"))
+        XCTAssert(stderr.contains("Sample.raiseSignal"))
+    }
+
+    func runSample(reason: String) throws -> String {
         let pipe = Pipe()
         let process = Process()
         process.executableURL = URL(fileURLWithPath: "/usr/bin/swift")
-        process.arguments = ["run", "Sample", expectedError]
+        process.arguments = ["run", "Sample", reason]
         process.standardError = pipe
-        XCTAssertNoThrow(try process.run())
-        if process.isRunning {
-            process.waitUntilExit()
-        }
-        let stderr = String(data: pipe.fileHandleForReading.readDataToEndOfFile(), encoding: .utf8) ?? ""
-        print(stderr)
-        XCTAssert(stderr.contains("Current stack trace:"), "expected stanard error to include backtrace")
-        XCTAssert(stderr.contains("Fatal error: \(expectedError)"), "expected stanard error to include error information")
-        #endif
+        try process.run()
+        process.waitUntilExit()
+        return String(data: pipe.fileHandleForReading.readDataToEndOfFile(), encoding: .utf8) ?? ""
     }
 }

docker/Dockerfile

@@ -17,20 +17,18 @@ RUN apt-get update && apt-get install -y wget
 RUN apt-get update && apt-get install -y lsof dnsutils netcat-openbsd net-tools curl jq # used by integration tests
 
 # ruby and jazzy for docs generation
-RUN apt-get update && apt-get install -y ruby ruby-dev libsqlite3-dev
-RUN gem install jazzy --no-ri --no-rdoc
+RUN apt-get update && apt-get install -y ruby ruby-dev libsqlite3-dev build-essential
+# jazzy no longer works on older version of ubuntu as ruby is too old.
+RUN if [ "${ubuntu_version}" = "focal" ] ; then echo "gem: --no-document" > ~/.gemrc ; fi
+RUN if [ "${ubuntu_version}" = "focal" ] ; then gem install jazzy ; fi
 
 # tools
 RUN mkdir -p $HOME/.tools
 RUN echo 'export PATH="$HOME/.tools:$PATH"' >> $HOME/.profile
 
-# script to allow mapping framepointers on linux (until part of the toolchain)
-RUN wget -q https://raw.githubusercontent.com/apple/swift/master/utils/symbolicate-linux-fatal -O $HOME/.tools/symbolicate-linux-fatal
-RUN chmod 755 $HOME/.tools/symbolicate-linux-fatal
-
 # swiftformat (until part of the toolchain)
 
-ARG swiftformat_version=0.44.0
+ARG swiftformat_version=0.44.6
 RUN git clone --branch $swiftformat_version --depth 1 https://github.com/nicklockwood/SwiftFormat $HOME/.tools/swift-format
 RUN cd $HOME/.tools/swift-format && swift build -c release
 RUN ln -s $HOME/.tools/swift-format/.build/release/swiftformat $HOME/.tools/swiftformat

docker/docker-compose.1804.52.yaml

@@ -6,7 +6,8 @@ services:
     image: swift-linux-backtrace:18.04-5.2
     build:
       args:
-        base_image: "swiftlang/swift:nightly-5.2-bionic"
+        ubuntu_version: "bionic"
+        swift_version: "5.2"
 
   test:
     image: swift-linux-backtrace:18.04-5.2

docker/docker-compose.1804.53.yaml

@@ -0,0 +1,16 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-linux-backtrace:18.04-5.3
+    build:
+      args:
+        ubuntu_version: "bionic"
+        swift_version: "5.3"
+
+  test:
+    image: swift-linux-backtrace:18.04-5.3
+
+  shell:
+    image: swift-linux-backtrace:18.04-5.3

docker/docker-compose.2004.54.yaml

@@ -0,0 +1,16 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-linux-backtrace:20.04-5.4
+    build:
+      args:
+        ubuntu_version: "focal"
+        swift_version: "5.4"
+
+  test:
+    image: swift-linux-backtrace:20.04-5.4
+
+  shell:
+    image: swift-linux-backtrace:20.04-5.4

docker/docker-compose.2004.55.yaml

@@ -0,0 +1,16 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-linux-backtrace:20.04-5.5
+    build:
+      args:
+        ubuntu_version: "focal"
+        swift_version: "5.5"
+
+  test:
+    image: swift-linux-backtrace:20.04-5.5
+
+  shell:
+    image: swift-linux-backtrace:20.04-5.5

docker/docker-compose.2004.56.yaml

@@ -0,0 +1,16 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-linux-backtrace:20.04-5.6
+    build:
+      args:
+        ubuntu_version: "focal"
+        swift_version: "5.6"
+
+  test:
+    image: swift-linux-backtrace:20.04-5.6
+
+  shell:
+    image: swift-linux-backtrace:20.04-5.6

docker/docker-compose.2004.57.yaml

@@ -0,0 +1,15 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-linux-backtrace:20.04-5.7
+    build:
+      args:
+        base_image: "swiftlang/swift:nightly-main-focal"
+
+  test:
+    image: swift-linux-backtrace:20.04-5.7
+
+  shell:
+    image: swift-linux-backtrace:20.04-5.7

docker/docker-compose.2004.main.yaml

@@ -0,0 +1,15 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-linux-backtrace:20.04-main
+    build:
+      args:
+        base_image: "swiftlang/swift:nightly-main-focal"
+
+  test:
+    image: swift-linux-backtrace:20.04-main
+
+  shell:
+    image: swift-linux-backtrace:20.04-main

docker/docker-compose.yaml

@@ -34,4 +34,4 @@ services:
 
   shell:
     <<: *common
-    entrypoint: /bin/bash
+    entrypoint: /bin/bash -l