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Linker error with u32::to_ne_bytes and map #88549

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Linker error with u32::to_ne_bytes and map#88549
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A-const-genericsArea: const generics (parameters and arguments)A-linkageArea: linking into static, shared libraries and binariesA-monomorphizationArea: MonomorphizationC-bugCategory: This is a bug.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Description

@ejmount
ejmount
opened on Aug 31, 2021

I tried this code (playground example)

#![allow(incomplete_features)]
#![feature(const_generics)]

pub fn main() {
    // this causes a linker error if const_generics is enabled
    let _ = [0; 1].map(u32::to_ne_bytes);
    
    // but this does not!
    //let _ = [0; 1].map(|x| u32::to_ne_bytes(x));
}

I expected to see this happen: a compile error. And also, I particularly expect map(foo) and map(|x| foo(x)) to behave similarly.

Instead, this happened: the linker falls over:

error: linking with `cc` failed: exit status: 1
  |
  = note: "cc" "-m64" "/playground/target/debug/deps/playground-4c173013dcdff931.playground.8c85a93c-cgu.0.rcgu.o" "/playground/target/debug/deps/playground-4c173013dcdff931.12vh8z6qs538xs91.rcgu.o" "-Wl,--as-needed" "-L" "/playground/target/debug/deps" "-L" "/playground/target/debug/build/libsqlite3-sys-0d351e27eaa1e97b/out" "-L" "/playground/target/debug/build/ring-38bf9793e960dc3f/out" "-L" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,--start-group" "-Wl,-Bstatic" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd-03b16363306a53dd.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libpanic_unwind-4695c0f6311791db.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libminiz_oxide-1a282f8b292d9e3f.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libadler-a54ae5159230894d.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libobject-13671d003abcccd5.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libmemchr-7509adad918d4b3b.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libaddr2line-66d0be1f7efaf5ca.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libgimli-41443b46a1557b2c.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd_detect-60812e99072283ff.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_demangle-412d545269c27063.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libhashbrown-0dbc7e011696d844.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_std_workspace_alloc-78b2343cc72ff57a.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libunwind-65fa19680bfb5ee4.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcfg_if-72cab8079f9b3b1e.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/liblibc-32d13a5363efe47b.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/liballoc-9ee1d5d15e6abbeb.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_std_workspace_core-52d5241975807511.rlib" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-9924c22ae1efcf66.rlib" "-Wl,--end-group" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-96219fb718f2f3e8.rlib" "-Wl,-Bdynamic" "-lgcc_s" "-lutil" "-lrt" "-lpthread" "-lm" "-ldl" "-lc" "-Wl,--eh-frame-hdr" "-Wl,-znoexecstack" "-L" "/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-o" "/playground/target/debug/deps/playground-4c173013dcdff931" "-Wl,--gc-sections" "-pie" "-Wl,-zrelro" "-Wl,-znow" "-nodefaultlibs"
  = note: /usr/bin/ld: /playground/target/debug/deps/playground-4c173013dcdff931.playground.8c85a93c-cgu.0.rcgu.o: in function `core::array::collect_into_array':
          /rustc/5d6804469d80aaf26f98090ae016af45e267f58f/library/core/src/array/mod.rs:506: undefined reference to `core::mem::maybe_uninit::MaybeUninit<T>::uninit_array'
          /usr/bin/ld: /rustc/5d6804469d80aaf26f98090ae016af45e267f58f/library/core/src/array/mod.rs:485: undefined reference to `core::mem::zeroed'
          /usr/bin/ld: /rustc/5d6804469d80aaf26f98090ae016af45e267f58f/library/core/src/array/mod.rs:508: undefined reference to `core::mem::maybe_uninit::MaybeUninit<T>::slice_as_mut_ptr'
          /usr/bin/ld: /rustc/5d6804469d80aaf26f98090ae016af45e267f58f/library/core/src/array/mod.rs:515: undefined reference to `core::slice::<impl [T]>::get_unchecked_mut'
          /usr/bin/ld: /rustc/5d6804469d80aaf26f98090ae016af45e267f58f/library/core/src/array/mod.rs:515: undefined reference to `core::mem::maybe_uninit::MaybeUninit<T>::write'
          /usr/bin/ld: /rustc/5d6804469d80aaf26f98090ae016af45e267f58f/library/core/src/array/mod.rs:521: undefined reference to `core::mem::forget'
          /usr/bin/ld: /rustc/5d6804469d80aaf26f98090ae016af45e267f58f/library/core/src/array/mod.rs:525: undefined reference to `core::mem::maybe_uninit::MaybeUninit<T>::array_assume_init'
          /usr/bin/ld: /playground/target/debug/deps/playground-4c173013dcdff931: hidden symbol `_ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$17get_unchecked_mut17hab68e22870af8369E' isn't defined
          /usr/bin/ld: final link failed: bad value
          collect2: error: ld returned 1 exit status
          
  = help: some `extern` functions couldn't be found; some native libraries may need to be installed or have their path specified
  = note: use the `-l` flag to specify native libraries to link
  = note: use the `cargo:rustc-link-lib` directive to specify the native libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#cargorustc-link-libkindname)

Activity

  1. ejmount
    added
    C-bugCategory: This is a bug.
    on Aug 31, 2021

  2. hellow554 commented on Sep 1, 2021

    @hellow554
    hellow554
    on Sep 1, 2021
    Contributor

    It looks like you are using an oder version of rustc? Can you post your version please (rustc -vV). In the meantime, use rustup update to update your compiler.

    I can't see the error anymore on the latest nightly

    Wow, this is funny!

    So feature(const_generics) is now "removed" (in #88369) and replaced by either adt_const_params or generic_const_exprs. If you choose the first, the program will compile fine and gives no warning and even runs as intended.

    But if you choose the later, the program will error out with the exact same message as @ejmount described.

    Second fun fact, if the second map isn't commeted out (and the still one is still in place) the program will compile fine in both configurations.

  3. Rain336 commented on Sep 2, 2021

    @Rain336
    Rain336
    on Sep 2, 2021

    Sounds to me like a monomorpization problem! It seams like the first example doesn't create a monomorpized version of the u32::to_ne_bytes function, but still references it! That would also explain why it would work if the second example is enabled, since that one would correctly generate a monomorpized version of u32::to_ne_bytes, which can then be used by the first example!

  4. ChrisDenton
    added
    needs-triage-legacy
    on Jul 16, 2023
  5. fmease
    added
    A-linkageArea: linking into static, shared libraries and binaries
    T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.
    A-const-genericsArea: const generics (parameters and arguments)
    A-monomorphizationArea: Monomorphization
    and removed
    needs-triage-legacy
    on Jan 26, 2024

  6. fmease commented on Jan 26, 2024

    @fmease
    fmease
    on Jan 26, 2024
    Member

    I can no longer reproduce this even if I follow

    So feature(const_generics) is now "removed" (in #88369) and replaced by either adt_const_params or generic_const_exprs. If you choose the first, the program will compile fine and gives no warning and even runs as intended.

    Closing as fixed. Please ping me if I missed anything.

  7. fmease
    closed this as completedon Jan 26, 2024
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    A-const-genericsArea: const generics (parameters and arguments)A-linkageArea: linking into static, shared libraries and binariesA-monomorphizationArea: MonomorphizationC-bugCategory: This is a bug.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

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