How do I compile swift without any dynamic libraries? - swift

Question

Tring to make a "hello, world" style program to see if I can use Swift on the web by running it through emscripten to get asm.js output.
The problem is that when I compile it, its bitcode tries to link dynamic libraries. It doesn't seem like it should need to do this, or it seems like someone who understands how all these pieces fit together could tell me how to provide the file it needs (I'm willing to implement some of the functions it depends on in JavaScript, if necessary).
I have a more comprehensive explanation of the environment here, but this is the basics:
The file:
$ cat f.swift
var message = 1
Compile it to bitcode:
$ xcrun swiftc -emit-bc f.swift -o f.bc
Fail to compile the bitcode to asm.js:
$ emcc f.bc
WARNING: Linking two modules of different data layouts: '/Users/josh/.emscripten_cache/libc.bc' is 'e-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-p:32:32:32-v128:32:128-n32-S128' whereas '/Users/josh/deleteme/swift-play/f.bc' is 'e-m:o-i64:64-f80:128-n8:16:32:64-S128'
WARNING: Linking two modules of different target triples: /Users/josh/.emscripten_cache/libc.bc' is 'asmjs-unknown-emscripten' whereas '/Users/josh/deleteme/swift-play/f.bc' is 'x86_64-apple-darwin13.2.0'
Unknown specifier in datalayout string
UNREACHABLE executed at /Users/clb/emscripten-fastcomp/lib/IR/DataLayout.cpp:300!
0 opt 0x00000001086d04ae llvm::sys::PrintStackTrace(__sFILE*) + 46
1 opt 0x00000001086d07bb PrintStackTraceSignalHandler(void*) + 27
2 opt 0x00000001086d0b4c SignalHandler(int) + 412
3 libsystem_platform.dylib 0x00007fff8b0e35aa _sigtramp + 26
4 libsystem_platform.dylib 0x00007fff6492d380 _sigtramp + 3649347056
5 opt 0x00000001086d07eb raise + 27
6 opt 0x00000001086d08a2 abort + 18
7 opt 0x000000010865a7a6 llvm::llvm_unreachable_internal(char const*, char const*, unsigned int) + 198
8 opt 0x0000000108416b74 llvm::DataLayout::parseSpecifier(llvm::StringRef) + 2804
9 opt 0x0000000108415c57 llvm::DataLayout::init(llvm::StringRef) + 471
10 opt 0x000000010749b47e llvm::DataLayout::DataLayout(llvm::StringRef) + 158
11 opt 0x0000000107482ba5 llvm::DataLayout::DataLayout(llvm::StringRef) + 37
12 opt 0x000000010747943c main + 3756
13 libdyld.dylib 0x00007fff8a2865fd start + 1
Stack dump:
0. Program arguments: /Users/josh/code/emsdk_portable/clang/e1.25.0_64bit/opt /var/folders/7g/mbft22555w3_2nqs_h1kbglw0000gn/T/tmp93OFuV/a.out.bc -strip-debug -internalize -internalize-public-api-list=main,malloc,free -globaldce -pnacl-abi-simplify-preopt -pnacl-abi-simplify-postopt -enable-emscripten-cxx-exceptions -o /var/folders/7g/mbft22555w3_2nqs_h1kbglw0000gn/T/tmp93OFuV/a.out.bc.opt.bc
Traceback (most recent call last):
File "/Users/josh/code/emsdk_portable/emscripten/1.25.0/emcc", line 1224, in <module>
shared.Building.llvm_opt(final, link_opts)
File "/Users/josh/code/emsdk_portable/emscripten/1.25.0/tools/shared.py", line 1357, in llvm_opt
assert os.path.exists(target), 'Failed to run llvm optimizations: ' + output
AssertionError: Failed to run llvm optimizations:

Answer 1

Looks like you're out of luck here. The IR compiler is generating is not standard - it includes some private Apple changes which were not upstreamed (in particular, the data layout string is non-standard at least).
And no, it is not trying to link any dynamic libraries. It tries to link statically (at LLVM IR level) all necessary stuff, in particular, C standard library.