Open Radar

 
The following configuration will cause the Swift compiler to crash when run from the commandline using -frontend -c. Every piece of this is required; very small modifications may avoid the crash, though some changes can cause the compiler to appear to hang.

* There must be at least two swift files, not including main.
* What is in main and the second swift file is unimportant (they can be empty)
* The crashing file looks like this:

—
struct A {
    let x = UInt8(0)
    let y = 0
}

let a = A()
let b = a
—

Each line is required, and order within the struct matters. This compiles fine within Xcode, but if compiled from the commandline (swift/swiftc or xcodebuild), it will crash. The simplest commandline that will crash it is (every piece of this is required; compiling other ways may work):

swift -frontend -c -primary-file crasher.swift other.swift -O

(In order for this project to compile in Xcode, there must also be a main.swift, but it is not required in order to demonstrate the problem.)

The crash:

0  swift                    0x00000001027b6edb llvm::sys::PrintStackTrace(__sFILE*) + 43
1  swift                    0x00000001027b761b SignalHandler(int) + 379
2  libsystem_platform.dylib 0x00007fff95156f1a _sigtramp + 26
3  swift                    0x0000000100a00862 swift::CanType swift::CanTypeVisitor<(anonymous namespace)::SubstDependentSILType<swift::SILFunction::mapTypeIntoContext(swift::SILType) const::$_0>, swift::CanType>::visit<>(swift::CanType) + 66
4  swift                    0x0000000100947764 llvm::StringMap<llvm::Constant*, llvm::MallocAllocator>::insert(std::__1::pair<llvm::StringRef, llvm::Constant*>) + 36
5  swift                    0x0000000100944fc5 swift::irgen::IRGenModule::getAddrOfGlobalUTF16String(llvm::StringRef) + 101
6  swift                    0x00000001009da402 getConstantValue(swift::irgen::IRGenModule&, llvm::StructType*, swift::StructInst*) + 450
7  swift                    0x00000001009da1e2 swift::irgen::IRGenModule::emitSILStaticInitializer() + 194
8  swift                    0x00000001009419aa swift::irgen::IRGenModuleDispatcher::emitGlobalTopLevel() + 490
9  swift                    0x00000001009c0f39 performIRGeneration(swift::IRGenOptions&, swift::ModuleDecl*, swift::SILModule*, llvm::StringRef, llvm::LLVMContext&, swift::SourceFile*, unsigned int) + 793
10 swift                    0x00000001009c13b0 swift::performIRGeneration(swift::IRGenOptions&, swift::SourceFile&, swift::SILModule*, llvm::StringRef, llvm::LLVMContext&, unsigned int) + 64
11 swift                    0x00000001008c88a8 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&) + 13704
12 swift                    0x00000001008c510a frontend_main(llvm::ArrayRef<char const*>, char const*, void*) + 2682
13 swift                    0x00000001008c1797 main + 2247
14 libdyld.dylib            0x00007fff8cf0f5c9 start + 1
15 libdyld.dylib            0x0000000000000007 start + 1930365503
Stack dump:
0.	Program arguments: /Applications/Xcode 7.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c -primary-file crasher.swift other.swift -O
Segmentation fault: 11

Attached is an example project to demonstrate.