Linking error on Windows when recreating a slice from raw parts

[pcwiek]

Background

I wanted to expose a Rust library that would expose C-compatible API & ABI and would be used from C-like platform. What I need to do first is populate an array of structs.

Example

use std::slice;

#[repr(C)]
pub struct Item {
    num: i32,
    acc: i32,
}

#[no_mangle]
pub extern fn fill(arr: *mut Item, arr_size: i32) {
    let arr = unsafe { slice::from_raw_parts_mut(arr, arr_size as usize) };

    let mut sum = 0;

    for (i, item) in arr.iter_mut().enumerate() {
        item.num = (i + 1) as i32;
        item.acc = {sum += item.num; sum};
    }
}

Now when I try to compile that using latest Rust 1.0.0-beta5, I get linking errors:

error: linking with gcc failed: exit code: 1 note: "gcc" "-Wl,--enable-long-section-names" "-fno-use-linker-plugin" "-Wl,--nxcompat" "-Wl,--large-address-aware" "-shared-libgcc" "-L" "C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib" "-o" "C:\Projects\Personal\ALR\target\debug\ALR.dll" "C:\Projects\Personal\ALR\target\debug\ALR.o" "C:\Projects\Personal\ALR\target\debug\ALR.metadata.o" "C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib\libstd-4e7c5e5c.rlib" "C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib\libcollections-4e7c5e5c.rlib" "C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib\libunicode-4e7c5e5c.rlib" "C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib\librand-4e7c5e5c.rlib" "C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib\liballoc-4e7c5e5c.rlib" "C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib\liblibc-4e7c5e5c.rlib" "C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib\libcore-4e7c5e5c.rlib" "-L" "C:\Projects\Personal\ALR\target\debug" "-L" "C:\Projects\Personal\ALR\target\debug\deps" "-L" "C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib" "-L" "C:\Projects\Personal\ALR\src.rust\bin\i686-pc-windows-gnu" "-L" "C:\Projects\Personal\ALR\src\bin\i686-pc-windows-gnu" "-Wl,--whole-archive" "-Wl,-Bstatic" "-Wl,--no-whole-archive" "-Wl,-Bdynamic" "-lws2_32" "-luserenv" "-shared" "-lcompiler-rt"
note:
C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib\libcore-4e7c5e5c.rlib(core-4e7c5e5c.o):(.text+0x3ab4): undefined reference to rust_begin_unwind'
C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib\libcore-4e7c5e5c.rlib(core-4e7c5e5c.o):(.eh_frame+0x5c7f): undefined reference to rust_eh_personality'
ld: C:\Rust\bin\rustlib\i686-pc-windows-gnu\lib\libcore-4e7c5e5c.rlib(core-4e7c5e5c.o): bad reloc address 0x5c7f in section `.eh_frame'

If I add empty println somewhere in the loop:

for (i, item) in arr.iter_mut().enumerate() {
    println!("");    
    item.num = (i + 1) as i32;
    item.acc = {sum += item.num; sum};
}

Linking actually works.

Unfortunately, when using the DLL in the third party platform, I'm getting stack overflow exception in the library (?!). That only happens when working with arrays though (iterating over a slice created from raw array, for example), passing a singular C struct by reference works just fine.

[barosl]

Nice to see an issue related to Windows be filed! Just to be complete, could you tell us what steps are needed to reproduce the bug? Also the contents of Cargo.toml.

[pcwiek]

Sure!

1. Install x86 Rust for Windows (.exe)
2. cargo new ALR
3. Paste the code from the example example into lib.rs
4. cargo build
5. Wade through the crash dump :)

Cargo.toml contents:

[package]
name = "ALR"
version = "0.1.0"
authors = ["pcwiek <mail@redacted-i-dont-like-bots.com>"]

[lib]
name = "ALR"
crate-type = ["dylib"]

Cargo version

C:\Projects\Personal\ALR>cargo -V
cargo 0.2.0-nightly (efb482d 2015-04-30) (built 2015-04-30)

Rust version

C:\Projects\Personal\ALR>rustc -V
rustc 1.0.0-beta.5 (7b4ef47 2015-05-11) (built 2015-05-11)

[alexcrichton]

I've often seen this problem arise when the target architecture for gcc/rustc don't match, are you sure that you're matching a 32/64bit rustc with the same bit-ness of gcc? Alternatively, are you running the compiler outside of MinGW (in which case the answer to the first question is yes!)

[pcwiek]

@alexcrichton Well, I just installed x86 Rust package, mostly because I need x86 DLL and I didn't want to fiddle with different target architecture when using x64 Windows package etc. I don't have any other MinGW/GCC installation, so I assumed that whatever came bundled with Rust was a-OK.

I use cargo to build/test the project, although I'm not exactly sure if that answers your second question :)

Also I'm not sure why linking actually passes after adding println!("") to the loop...

[alexcrichton]

Ah I think I see what's going now, I believe this is a dupe of #18807, so closing in favor of that. Thanks for the report though!