ICE: no_core

[Zymlex]

Code

#![no_std]
#![no_core]
#![no_main]
#![feature(no_core, lang_items)]

#[lang = "sized"]
trait Sized {}
#[lang = "sync"]
trait Sync {}
#[lang = "copy"]
trait Copy {}
#[lang = "freeze"]
trait Freeze {}

impl Sync for u32 {}
impl Sync for i32 {}

// impl Copy for u32 {} // if remove, it cause rustc crash

#[lang = "drop_in_place"]
#[allow(unconditional_recursion)]
pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) { unsafe { drop_in_place(to_drop) } }

#[link(name = "Kernel32")]
extern "system" {
    pub fn ExitProcess(uexitcode: u32) -> !;
}

fn exit_process(exit_code: u32) -> ! { // Copying is necessary to pass the value through the function argument, and if this is avoided, there will be no error either.
    unsafe {
        ExitProcess(exit_code);
    }
}

#[no_mangle]
pub extern "C" fn wWinMainCRTStartup() -> i32 {
    exit_process(0);
}

#[no_mangle]
pub static _fltused: i32 = 1;

similar https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=7a195a8a96465739641bc5b737854d10

Cargo.toml:

[profile.release]
rustflags = [
    '-C', 'link-args=/NODEFAULTLIB /Zl /SUBSYSTEM:WINDOWS /SAFESEH:NO /DYNAMICBASE:NO /ENTRY:wWinMainCRTStartup /LTCG'
]
panic = "abort"

Meta

rustc --version --verbose:

rustc 1.63.0-nightly (ec55c6130 2022-06-10)
binary: rustc
commit-hash: ec55c61305eaf385fc1b93ac9a78284b4d887fe5
commit-date: 2022-06-10
host: x86_64-pc-windows-msvc
release: 1.63.0-nightly
LLVM version: 14.0.5

Error output

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: broken MIR in DefId(0:11 ~ test_no_core[9a43]::exit_process) (NoSolution): could not prove Binder(TraitPredicate(<u32 as Copy>, polarity:Positive), [])
  |
  = note: delayed at compiler\rustc_borrowck\src\type_check\canonical.rs:151:13

thread 'rustc' panicked at 'Box<dyn Any>', compiler\rustc_errors\src\lib.rs:1373:13
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md
note: rustc 1.63.0-nightly (ec55c6130 2022-06-10) running on x86_64-pc-windows-msvc
note: compiler flags: --crate-type bin -C opt-level=3 -C link-args=/NODEFAULTLIB /Zl /SUBSYSTEM:WINDOWS /SAFESEH:NO /DYNAMICBASE:NO /ENTRY:wWinMainCRTStartup /LTCG -C panic=abort -C lto=fat -C codegen-units=1 -C incremental -Z macro-backtrace
note: some of the compiler flags provided by cargo are hidden
query stack during panic:
end of query stack
error: could not compile `test`; 3 warnings emitted
Process finished with exit code 101

Backtrace

stack backtrace:
   0:     0x7ffcc6c09d1f - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h5878974d3101c2c1
   1:     0x7ffcc6c44d6a - core::fmt::write::h58b91005b62f62cb
   2:     0x7ffcc6bfc119 - <std::io::IoSlice as core::fmt::Debug>::fmt::h47ce2c587850b386
   3:     0x7ffcc6c0d60b - std::panicking::default_hook::h1cf6e1ccf8670b6e
   4:     0x7ffcc6c0d28b - std::panicking::default_hook::h1cf6e1ccf8670b6e
   5:     0x7ffcb68eb786 - rustc_driver[a11d5e36637d6ef8]::pretty::print_after_hir_lowering
   6:     0x7ffcc6c0ddb2 - std::panicking::rust_panic_with_hook::h8d89018be48b3be7
   7:     0x7ffcbb0b9ae5 - <rustc_errors[233cc4104dd9fe30]::styled_buffer::StyledChar as core[23edea91be4138c2]::fmt::Debug>::fmt
   8:     0x7ffcbb0b5969 - <rustc_errors[233cc4104dd9fe30]::styled_buffer::StyledChar as core[23edea91be4138c2]::fmt::Debug>::fmt
   9:     0x7ffcbb3fadf9 - rustc_query_system[4ba9814639d8c6d8]::query::plumbing::incremental_verify_ich_cold
  10:     0x7ffcbb0649a9 - <rustc_feature[80ac22f20521dda7]::builtin_attrs::AttributeType as core[23edea91be4138c2]::fmt::Debug>::fmt
  11:     0x7ffcbb0686dc - <rustc_errors[233cc4104dd9fe30]::HandlerInner as core[23edea91be4138c2]::ops::drop::Drop>::drop
  12:     0x7ffcb686cd64 - <rustc_lint[6c4a321fe5b8ec79]::BuiltinCombinedModuleLateLintPass as rustc_lint[6c4a321fe5b8ec79]::passes::LateLintPass>::check_mod_post
  13:     0x7ffcb68717ba - <rustc_lint[6c4a321fe5b8ec79]::BuiltinCombinedModuleLateLintPass as rustc_lint[6c4a321fe5b8ec79]::passes::LateLintPass>::check_mod_post
  14:     0x7ffcb68e40fd - <rustc_middle[fa74f14430eff12]::ty::SymbolName as core[23edea91be4138c2]::fmt::Debug>::fmt
  15:     0x7ffcb68e2319 - <rustc_middle[fa74f14430eff12]::ty::SymbolName as core[23edea91be4138c2]::fmt::Debug>::fmt
  16:     0x7ffcb687846d - <rustc_lint[6c4a321fe5b8ec79]::BuiltinCombinedModuleLateLintPass as rustc_lint[6c4a321fe5b8ec79]::passes::LateLintPass>::check_mod_post
  17:     0x7ffcb68dee76 - <rustc_metadata[7439ebc3b5fbc24c]::rmeta::encoder::EncodeContext as rustc_serialize[3bc617203079c8a5]::serialize::Encoder>::emit_raw_bytes
  18:     0x7ffcb68a2398 - <rustc_driver[a11d5e36637d6ef8]::args::Error as core[23edea91be4138c2]::fmt::Debug>::fmt
  19:     0x7ffcc6c1ef5c - std::sys::windows::thread::Thread::new::h40e1d95cdd0a661f
  20:     0x7ffcf5d47974 - BaseThreadInitThunk
  21:     0x7ffcf86ca2f1 - RtlUserThreadStart

[compiler-errors]

This ICE is expected because there are certain assumptions the compiler makes about built-in types. In this case, it's that u32 implements Copy. For example, that assumption is hard-coded here, in Ty::is_trivially_pure_clone_copy.

I think there's a general assumption that #![no_core] programs will ICE in a large number of cases unless very carefully written, and ICEs due to #![no_core] should not be investigated in general.

[Zymlex]

I think there's a general assumption that #![no_core] programs will ICE in a large number of cases unless very carefully written, and ICEs due to #![no_core] should not be investigated in general.

Then no_core will not be stabilized in the foreseeable future.
I understand that this is created for a limited number of people and not for samples like mine.

[eggyal]

I think there's a general assumption that #![no_core] programs will ICE in a large number of cases unless very carefully written, and ICEs due to #![no_core] should not be investigated in general.

Contradicts #29639 (comment):

ICEs need to be reported and fixed in most cases, even in no_core.

[compiler-errors]

@eggyal, this summarizes my opinions on #![no_core] ICEs a bit better:

#92495 (comment)

Personally, I don't think ICEs with #![no_core] are worth addressing. It's a perma-unstable feature, and lang items are effectively internal compiler code that happens to be written in a crate. We don't try to prevent ICEs in the face of modifications to the compiler itself (in fact, many internal compiler APIs will deliberately ICE when they are used incorrectly).

The only correct way to use #![no_core] is to copy-paste all of the lang items, types, and impls that you're using (and even then, leaving out "unused" ones is pretty dubious).

And regardless, this is a duplicate of that issue #92495.

[eggyal]

Ah, thanks for that. I've quoted it over in the tracking issue too.

[bjorn3]

@Zymlex Using #![no_std] in combination with LTO to allow whole program dead code elimination should give the same size benefits as using #![no_core] I think.

[Zymlex]

@Zymlex Using #![no_std] in combination with LTO to allow whole program dead code elimination should give the same size benefits as using #![no_core] I think.

I was interested in the possibility of creating a program without core.

[langston-barrett]

Minimized with Icemelter:

#![no_core]
#![feature(no_core, lang_items)]
#[lang = "sized"]
trait Sync {}
#[lang = "copy"]
trait Freeze {}

extern "C" {
    fn ExitProcess(uexitcode: u32) -> !;
}

fn exit_process(exit_code: u32) -> ! {
    unsafe {
        ExitProcess(exit_code);
    }
}

Details

Icemelter version: v0.2.0

@rustbot label +S-bug-has-mcve