Missing cabi_realloc on wasm-wasip2 with no_std when using exported resource

[Exidex]

Reproduction:

Cargo.toml

[package]
name = "cabi-realloc-repro"
version = "0.1.0"
edition = "2021"

[lib]
crate-type = ["cdylib"]

[dependencies]
wit-bindgen = { version = "0.60.0", default-features = false, features = ["macros", "realloc"] }
dlmalloc = { version = "0.2", features = ["global"] }

src/lib.rs

#![no_std]
extern crate alloc;

use core::panic::PanicInfo;

#[global_allocator]
static ALLOC: dlmalloc::GlobalDlmalloc = dlmalloc::GlobalDlmalloc;

#[panic_handler]
fn panic(_info: &PanicInfo) -> ! {
    loop {}
}

wit_bindgen::generate!({
    world: "repro",
    inline: r#"
        package test:repro;

        interface foo {
            resource bar {
                constructor(s: string);
            }
        }

        world repro {
            export foo;
        }
    "#,
});

struct Component;

impl exports::test::repro::foo::GuestBar for alloc::string::String {
    fn new(s: alloc::string::String) -> Self {
        s
    }
}

impl exports::test::repro::foo::Guest for Component {
    type Bar = alloc::string::String;
}

export!(Component);

Running:

cargo build --target wasm32-wasip2

returns

> cargo build --target wasm32-wasip2
   Compiling cabi-realloc-repro v0.1.0 (/home/exidex/IdeaProjects/project-fulcrum/repro)
error: linking with `wasm-component-ld` failed: exit status: 1
  |
  = note:  "wasm-component-ld" "-flavor" "wasm" "--export" "test:repro/foo#[constructor]bar" "--export" "test:repro/foo#[dtor]bar" "-z" "stack-size=1048576" "--stack-first" "--no-demangle" "<46 object files omitted>" "/home/exidex/IdeaProjects/project-fulcrum/repro/target/wasm32-wasip2/debug/deps/{libdlmalloc-a964d9799bfd317b,libcfg_if-b8d3e0e0e3728a15,libwit_bindgen-ac7e94936d930589}.rlib" "<sysroot>/lib/rustlib/wasm32-wasip2/lib/{liballoc-*,libcore-*,libcompiler_builtins-*}.rlib" "-L" "/home/exidex/IdeaProjects/project-fulcrum/repro/target/wasm32-wasip2/debug/build/wit-bindgen-3fa477ffebae6273/out" "-L" "<sysroot>/lib/rustlib/wasm32-wasip2/lib/self-contained" "-o" "/home/exidex/IdeaProjects/project-fulcrum/repro/target/wasm32-wasip2/debug/deps/cabi_realloc_repro.wasm" "--gc-sections" "--no-entry" "-O0"
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: error: failed to encode component
          
          Caused by:
              0: module does not export a function named `cabi_realloc`
          

error: could not compile `cabi-realloc-repro` (lib) due to 1 previous error

[alexcrichton]

The cabi_realloc function is expected to be provided by wasi-libc on the wasm32-wasip2 target, so if you're skipping using all that with no-std and such you'll need to define your own to work around this

[Exidex]

the only reason I've used no_std is to avoid rust-lang/rust#133235, which (in the limited amount of testing I've done) has worked so far, until I hit this specific wit structure. I couldn't get the cargo build command provided by you in the linked issue to work (after fixing the change with cargo's immediate-abort, it returned different linking error). Is there any other way to get rustc to not to import whole wasi into wasm component? or do I actually want to manually define cabi_realloc?

[Exidex]

Reproduction for linking issue with std

.cargo/config.toml

[unstable]
panic-immediate-abort = true

Cargo.toml

[package]
name = "repro-std"
version = "0.1.0"
edition = "2021"

[lib]
crate-type = ["cdylib"]

[dependencies]
wit-bindgen = { version = "0.60.0" }

[profile.release]
panic = "immediate-abort"

src/lib.rs

wit_bindgen::generate!({
    world: "repro",
    inline: r#"
        package test:reprostd;

        interface foo {
            resource bar {
                constructor(s: string);
            }
        }

        world repro {
            export foo;
        }
    "#,
});

struct Component;

impl exports::test::reprostd::foo::GuestBar for String {
    fn new(s: String) -> Self {
        s
    }
}

impl exports::test::reprostd::foo::Guest for Component {
    type Bar = String;
}

export!(Component);

Error

> cargo +nightly build -Zbuild-std=std,panic_abort --target wasm32-wasip2 --release
   Compiling repro-std v0.1.0 (/home/exidex/IdeaProjects/project-fulcrum/repro-std)
error: linking with `wasm-component-ld` failed: exit status: 1
  |
  = note:  "wasm-component-ld" "-flavor" "wasm" "--export" "test:reprostd/foo#[constructor]bar" "--export" "test:reprostd/foo#[dtor]bar" "--export" "cabi_realloc" "-z" "stack-size=1048576" "--stack-first" "--no-demangle" "<2 object files omitted>" "/home/exidex/IdeaProjects/project-fulcrum/repro-std/target/wasm32-wasip2/release/deps/{libwit_bindgen-ddf424ae13410e64,libbitflags-150fecc4fe1e70f7,libstd-7784b9645e417594,libwasip2-8b8a27b66195bd6d,libwit_bindgen-609ec4cc1b0fc616,libcfg_if-c230548bbc47c83b,librustc_demangle-30dbe7f3c8a74d65,libstd_detect-fd4d81680836c63b,libhashbrown-59044c1bd534824f,librustc_std_workspace_alloc-0f524fb0ddc72675,libminiz_oxide-b34234cf8afa2765,libadler2-8826c66e48d101e9,libunwind-b832139829831091,liblibc-7931c22797ae5dfa}.rlib" "-l" "c" "/home/exidex/IdeaProjects/project-fulcrum/repro-std/target/wasm32-wasip2/release/deps/{librustc_std_workspace_core-d44c7318566c92b3,liballoc-c2a5cc36a6b99be4,libcore-8fea76d2ec9acc6c,libcompiler_builtins-1ccdccd2c3f5f589}.rlib" "-L" "/home/exidex/IdeaProjects/project-fulcrum/repro-std/target/wasm32-wasip2/release/build/wit-bindgen-9c3900fb6d97bfd9/out" "-L" "/home/exidex/IdeaProjects/project-fulcrum/repro-std/target/wasm32-wasip2/release/build/wit-bindgen-3dc7b3d27a38969a/out" "-L" "<sysroot>/lib/rustlib/wasm32-wasip2/lib/self-contained" "-o" "/home/exidex/IdeaProjects/project-fulcrum/repro-std/target/wasm32-wasip2/release/deps/repro_std.wasm" "--gc-sections" "--no-entry" "-O3" "--strip-debug"
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: rust-lld: error: unable to find library -lc
          error: failed to invoke LLD: exit status: 1
          

error: could not compile `repro-std` (lib) due to 1 previous error

[alexcrichton]

Ok makes sense, for now with no_std you'll want to define your own cabi_realloc symbol. If you're using -Zbuild-std you'll have to specify -Clinker to an external wasi-sdk since that's what std depends on.

[Exidex]

Out of curiosity, what would the ideal fix for this look like so its not a such hassle to set this up? Can I track the progress somewhere?