Problem with passing struct to C function on windows

I prepared some files that should illustrate the problem: click

Struct Color is passed incorrectly to function in C library. I pass {1,2,3,4} but receive {1,0,0,0}.

It happens on Windows 7 64bit, but not on Linux Mint 64bit.
Using external LLVM to compile bitcode (on Windows) works too.

[alexcrichton]

Can you provide a slightly more minimized test case? It would also be useful to have content hosted in a github gist instead of a 7z archive that's much more easily accessible.

Sure: https://gist.github.com/krzat/8175981

[alexcrichton]

Thanks!

cc @jld, @nikomatsakis

[alexcrichton]

It appears that gcc treats the struct as an immediate 32-bit value (one register), and our call to the function generate a function call with 4 arguments. I would copy-paste more assembly, but I'm not sure how to copy out of a windows VM...

These parts are probably relevant:
https://gist.github.com/krzat/8181219#file-windows_external_llvm-asm-L34-L52
https://gist.github.com/krzat/8181219#file-windows_internal_llvm-asm-L43-L66

windows_internal_llvm.asm was generated by LLVM integrated with rust
windows_external_llvm.asm was generated by my own LLVM build and it works OK

Are there some parameters passed to integrated LLVM that could cause this?

I wrote a small utility to bypass the problem: https://gist.github.com/krzat/8374078
It worked with rsfml, though I guess rust uses LLVM fork for a reason.