use case: cross-compiling to macOS with a dependency on iconv

[hzuo]

Zig Version

0.9.0

Steps to Reproduce

Importantly, this was working fine on Zig 0.8.1.

On a Linux x86_64 system, with the following environment variables:

export CC="/tmp/zig/zig-cc.sh"
export RUSTFLAGS="-C linker=/tmp/zig/zig-cc.sh" # tells cargo which linker to use
export ZIG_CC_TARGET="x86_64-macos" # see below for zig-cc.sh

/tmp/zig/zig-cc.sh:

#!/usr/bin/env bash

zig cc -target "$ZIG_CC_TARGET" "$@"

Rust has the appropriate toolchain installed as well via rustup target add x86_64-apple-darwin.

Running the following fails:
cargo build --release --target x86_64-apple-darwin

Expected Behavior

Cross-compiling should succeed, as it previously did on 0.8.1.

Actual Behavior

The error message:

#18 25.26           + zig cc -target x86_64-macos -m64 -arch x86_64 /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.0.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.1.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.10.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.11.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.12.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.13.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.14.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.15.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.2.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.3.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.4.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.5.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.6.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.7.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.8.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.dataland_cli.1d4d3fd3-cgu.9.rcgu.o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2.1l6jpj3oj2sa9qhc.rcgu.o -L /workspace/target/x86_64-apple-darwin/release/deps -L /workspace/target/release/deps -L /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib /workspace/target/x86_64-apple-darwin/release/deps/libtracing_subscriber-121def450f384ec8.rlib /workspace/target/x86_64-apple-darwin/release/deps/libtracing_serde-1b1e201a0b2a4537.rlib /workspace/target/x86_64-apple-darwin/release/deps/libserde_json-3b25b60936215023.rlib /workspace/target/x86_64-apple-darwin/release/deps/libryu-ab0a6f0a7a7424d9.rlib /workspace/target/x86_64-apple-darwin/release/deps/libitoa-d2e7789291e807c0.rlib /workspace/target/x86_64-apple-darwin/release/deps/libserde-8ca663f1ba6ddb03.rlib /workspace/target/x86_64-apple-darwin/release/deps/libthread_local-2a1d6d7d5266e0d7.rlib /workspace/target/x86_64-apple-darwin/release/deps/libsharded_slab-4698239f188880b7.rlib /workspace/target/x86_64-apple-darwin/release/deps/libansi_term-a52ae630949588fb.rlib /workspace/target/x86_64-apple-darwin/release/deps/libtracing-3907d690e9347722.rlib /workspace/target/x86_64-apple-darwin/release/deps/libmatchers-56fdde59b4deb082.rlib /workspace/target/x86_64-apple-darwin/release/deps/libregex_automata-f2cefdfc3854ef00.rlib /workspace/target/x86_64-apple-darwin/release/deps/libregex-7cd7c076dda0dab5.rlib /workspace/target/x86_64-apple-darwin/release/deps/libregex_syntax-221c06f8a6a14612.rlib /workspace/target/x86_64-apple-darwin/release/deps/libtracing_log-de77fad8f7d69245.rlib /workspace/target/x86_64-apple-darwin/release/deps/libtracing_core-94d923876d1cd686.rlib /workspace/target/x86_64-apple-darwin/release/deps/libanyhow-8b91ea82dfb23487.rlib /workspace/target/x86_64-apple-darwin/release/deps/libbacktrace-a7571d3ce9bdaf1c.rlib /workspace/target/x86_64-apple-darwin/release/deps/libobject-26177e9e72dd48de.rlib /workspace/target/x86_64-apple-darwin/release/deps/libaddr2line-12ac3d7d499b72d5.rlib /workspace/target/x86_64-apple-darwin/release/deps/libgimli-e783ad841c63807b.rlib /workspace/target/x86_64-apple-darwin/release/deps/librustc_demangle-4264c06b0774ac65.rlib /workspace/target/x86_64-apple-darwin/release/deps/libtokio-a95341b0c068d924.rlib /workspace/target/x86_64-apple-darwin/release/deps/libsignal_hook_registry-e6aca81d26e7d74a.rlib /workspace/target/x86_64-apple-darwin/release/deps/libnum_cpus-c796ac8e638a7923.rlib /workspace/target/x86_64-apple-darwin/release/deps/libmemchr-b2f371f226219eb7.rlib /workspace/target/x86_64-apple-darwin/release/deps/libonce_cell-788000b5d451ef73.rlib /workspace/target/x86_64-apple-darwin/release/deps/libbytes-a4b23a77b0d5639d.rlib /workspace/target/x86_64-apple-darwin/release/deps/libmio-2ea0f919e831f7a1.rlib /workspace/target/x86_64-apple-darwin/release/deps/liblog-57b33a9561401c1c.rlib /workspace/target/x86_64-apple-darwin/release/deps/libpin_project_lite-95c272eb16590914.rlib /workspace/target/x86_64-apple-darwin/release/deps/libparking_lot-66e871389e7cfb65.rlib /workspace/target/x86_64-apple-darwin/release/deps/libparking_lot_core-0e4ee11b437dd388.rlib /workspace/target/x86_64-apple-darwin/release/deps/libsmallvec-2ece64d0efa93d4c.rlib /workspace/target/x86_64-apple-darwin/release/deps/liblock_api-f3d4fdfd0b0c4cda.rlib /workspace/target/x86_64-apple-darwin/release/deps/libscopeguard-3e1eb989dbc64aea.rlib /workspace/target/x86_64-apple-darwin/release/deps/libinstant-db126e86457b2752.rlib /workspace/target/x86_64-apple-darwin/release/deps/libcfg_if-6c282713920cb282.rlib /workspace/target/x86_64-apple-darwin/release/deps/libstructopt-ac4f8199383edc2f.rlib /workspace/target/x86_64-apple-darwin/release/deps/liblazy_static-dd7341373b83f87a.rlib /workspace/target/x86_64-apple-darwin/release/deps/libclap-30139c84668193d2.rlib /workspace/target/x86_64-apple-darwin/release/deps/libvec_map-74a07ca8f456d6ac.rlib /workspace/target/x86_64-apple-darwin/release/deps/libtextwrap-28cd32cd2b0263b2.rlib /workspace/target/x86_64-apple-darwin/release/deps/libunicode_width-13bdbd2bd29a774e.rlib /workspace/target/x86_64-apple-darwin/release/deps/libstrsim-cce460edd015dfaa.rlib /workspace/target/x86_64-apple-darwin/release/deps/libbitflags-b9b1828bf04cff48.rlib /workspace/target/x86_64-apple-darwin/release/deps/libatty-21ad3d79f2f21e38.rlib /workspace/target/x86_64-apple-darwin/release/deps/liblibc-39e24e4029278f6c.rlib /workspace/target/x86_64-apple-darwin/release/deps/libansi_term-9abb6ae0d5d4492f.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libstd-dd8a82589e0cba34.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libpanic_unwind-8c04c8bd0d1a8900.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libobject-c6a4ae86ed2c40d0.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libmemchr-f9ab4d1b2e38b05e.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libaddr2line-002c7b677ad6c512.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libgimli-a3f3d9f86c37973f.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libstd_detect-8b14bcf2354140fd.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/librustc_demangle-d6f2fd91ec8bbbcc.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libhashbrown-24c80e37fb5b15c5.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/librustc_std_workspace_alloc-edb9b11fa36b4795.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libunwind-769780536fb7ef9b.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libcfg_if-d37c37a3a3ac2b0c.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/liblibc-c1bdc4c1f89760ef.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/liballoc-750380e9c94de9ce.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/librustc_std_workspace_core-1108e622f5a15c3d.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libcore-43af7053e70b1eed.rlib /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib/libcompiler_builtins-3a81ebf6a3abbdee.rlib -liconv -lSystem -lresolv -lc -lm -liconv -L /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib -o /workspace/target/x86_64-apple-darwin/release/deps/dataland_cli-c446093d9b895ef2 -Wl,-dead_strip -nodefaultlibs
#18 25.26           warning: unsupported linker arg: -dead_strip
#18 25.26           warning(link): library not found for '-liconv'
#18 25.26           warning(link): Library search paths:
#18 25.26           warning(link):   /workspace/target/x86_64-apple-darwin/release/deps
#18 25.26           warning(link):   /workspace/target/release/deps
#18 25.26           warning(link):   /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib
#18 25.26           warning(link):   /usr/local/rustup/toolchains/1.57.0-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-apple-darwin/lib
#18 25.26           error: LibraryNotFound

Seems that 0.9.0 can't find iconv but 0.8.1 was able to?

[hzuo]

Seems related to #9725

[kubkon]

Since you're invoking Zig with -target flag, it enters cross-compilation mode so you will need to explicitly pass the sysroot and specify the search paths for include dirs, libraries and frameworks like so:

#!/usr/bin/env bash

zig cc -target "$ZIG_CC_TARGET" --sysroot=/path/to/sysroot -I/usr/include -L/usr/lib -F/System/Library/Frameworks "$@"

Note that this is also conditional on this fix #10568

[kubkon]

@hzuo OK, I seem to have misunderstood the issue, however, it is not a regression per se. Let me explain. The behaviour (and error) are actually correct. -liconv is required by Rust (as evidenced by its presence on the linker line) and it's available via macOS SDK, therefore you will need to provide the sysroot/SDK when cross-compiling Rust to macOS from a foreign host. The reason this was not an error before was because zig ld did not flag the missing library as error but rather as warning, and would link away. This is the only change in behaviour since 0.8. Also, FYI, I did provide the sysroot/SDK, and cross-linked basic hyper.rs hello-world example just fine.

@andrewrk do you think we should leave it at status quo of this being a hard error? I for one stand by this and believe it should always be a hard error.

[andrewrk]

Yes if you specify to link a library with -liconv then it must link iconv or report an error.

As for how to solve @hzuo's problem, they will need to provide an iconv to link against when cross compiling, or if possible, pass a build configuration option telling it to not depend on iconv.

If you wish to use zig cc to cross compile and you want to avoid a macOS SDK, I suggest to first cross-compile iconv with zig, then you will have a static iconv build that you can link against.

I will leave this open for a while as a "use case" to remind us that solving this problem somehow could help Rust folks - but there is a good chance that it will be eventually closed with no solution.