[swift-dev] JIT-ting Swift

Alex Denisov 1101.debian at gmail.com
Mon Mar 6 11:33:18 CST 2017

Hi there,

I could not find a list for swift-corelibs-xctest so I am posting it here.

I am trying to run tests based on XCTest (https://github.com/apple/swift-corelibs-xctest) using LLVM's JIT.
Everything is working good so far. However, I am getting a crash.
Based on a shallow investigation I can see that this is somehow related to the way Swift treats the command line arguments. Or, to be more precise, to the way I pass the arguments to the swift's 'main' function.

What I did so far is not different from what I do to run C or C++ using JIT:

auto main = ((int (*)(int, const char **))(intptr_t)mainPointer);
const int argc = 1;
const char *argv[] = { "some-name", NULL };
auto result = main(argc, argv);

Based on what I see in the IR[1] the 'argv' has type "%Sp = type <{ i8* }>", which seems to be a struct with a pointer to something.

So the question is: what is being passed as a second argument to the 'main' function of a swift program?

Any other advice on JIT-ting Swift are more than welcome :)

[1] https://gist.github.com/AlexDenisov/3c10540b544e82cfb6e58e1452491904
Software Engineer, https://lowlevelbits.org

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