[EXPERIMENT] Move handle_alloc_error to core

[clarfonthey]

Not meant to be merged as-is. This exists as a test that would be needed to make hashbrown no longer depend on alloc.

Currently, this method does not actually need to be in alloc, minus the cfg(not(no_global_oom_handling)), which could potentially be removed. It ultimately gets replaced with something reasonable in environments with std, but just aborts in no_std environments.

The unfortunate bit is that we can't change the stability of re-exported functions, and so, this makes the version in alloc a wrapper function.

[rust-log-analyzer]

The job x86_64-gnu-miri failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

tests/fail/tree_borrows/wildcard/subtree_internal_relatedness.rs ... ok
tests/fail/tree_borrows/wildcard/subtree_internal_relatedness_wildcard.rs ... ok

FAILED TEST: tests/fail/alloc/alloc_error_handler.rs
command: MIRI_ENV_VAR_TEST="0" MIRI_TEMP="/tmp/miri-uitest-kLghlF" RUST_BACKTRACE="1" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/release/miri" "--error-format=json" "-Dwarnings" "-Dunused" "-Ainternal_features" "-Zui-testing" "--sysroot=/checkout/obj/build/x86_64-unknown-linux-gnu/miri-sysroot" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/tmp/miri_ui/0/tests/fail/alloc" "tests/fail/alloc/alloc_error_handler.rs" "--edition" "2021"

error: actual output differed from expected
Execute `./miri test --bless` to update `tests/fail/alloc/alloc_error_handler.stderr` to the actual output
--- tests/fail/alloc/alloc_error_handler.stderr
+++ <stderr output>
---

Full unnormalized output:
memory allocation of 4 bytes failed
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
error: abnormal termination: the program aborted execution
##[error]  --> /checkout/library/std/src/alloc.rs:429:9
   |
LL |         crate::process::abort()
   |         ^^^^^^^^^^^^^^^^^^^^^^^ abnormal termination occurred here
   |
   = note: stack backtrace:
           0: std::alloc::rust_oom::{closure#0}
               at /checkout/library/std/src/alloc.rs:429:9: 429:32
           1: std::sys::backtrace::__rust_end_short_backtrace::<{closure@std::alloc::rust_oom::{closure#0}}, !>
               at /checkout/library/std/src/sys/backtrace.rs:182:18: 182:21
           2: std::alloc::rust_oom
               at /checkout/library/std/src/alloc.rs:424:5: 430:7
           3: std::alloc::_::__rust_alloc_error_handler
               at /checkout/library/std/src/alloc.rs:423:1: 423:37
           4: core::alloc::handle_alloc_error::rt_error
               at /checkout/library/core/src/alloc/mod.rs:516:13: 516:70
---

full stderr:
memory allocation of 4 bytes failed
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
error: abnormal termination: the program aborted execution
##[error]  --> /checkout/library/std/src/alloc.rs:429:9
   |
LL |         crate::process::abort()
   |         ^^^^^^^^^^^^^^^^^^^^^^^ abnormal termination occurred here
   |
   = note: stack backtrace:
           0: std::alloc::rust_oom::{closure#0}
               at /checkout/library/std/src/alloc.rs:429:9: 429:32
           1: std::sys::backtrace::__rust_end_short_backtrace::<{closure@std::alloc::rust_oom::{closure#0}}, !>
               at /checkout/library/std/src/sys/backtrace.rs:182:18: 182:21
           2: std::alloc::rust_oom
               at /checkout/library/std/src/alloc.rs:424:5: 430:7
           3: std::alloc::_::__rust_alloc_error_handler
               at /checkout/library/std/src/alloc.rs:423:1: 423:37
           4: core::alloc::handle_alloc_error::rt_error
               at /checkout/library/core/src/alloc/mod.rs:516:13: 516:70
---



FAILED TEST: tests/fail/alloc/alloc_error_handler_custom.rs
command: MIRI_ENV_VAR_TEST="0" MIRI_TEMP="/tmp/miri-uitest-kLghlF" RUST_BACKTRACE="1" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/release/miri" "--error-format=json" "-Dwarnings" "-Dunused" "-Ainternal_features" "-Zui-testing" "--sysroot=/checkout/obj/build/x86_64-unknown-linux-gnu/miri-sysroot" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/tmp/miri_ui/0/tests/fail/alloc" "tests/fail/alloc/alloc_error_handler_custom.rs" "-Cpanic=abort" "--edition" "2021"

error: actual output differed from expected
Execute `./miri test --bless` to update `tests/fail/alloc/alloc_error_handler_custom.stderr` to the actual output
--- tests/fail/alloc/alloc_error_handler_custom.stderr
+++ <stderr output>
 custom alloc error handler: Layout { size: 4, align: 4 (1 << 2) }
 error: abnormal termination: the program aborted execution
... 8 lines skipped ...
            1: _::__rust_alloc_error_handler
                at tests/fail/alloc/alloc_error_handler_custom.rs:LL:CC
-           2: alloc::alloc::handle_alloc_error::rt_error
---
 
 error: aborting due to 1 previous error
 

Full unnormalized output:
custom alloc error handler: Layout { size: 4, align: 4 (1 << 2) }
error: abnormal termination: the program aborted execution
##[error]  --> tests/fail/alloc/alloc_error_handler_custom.rs:19:5
   |
LL |     core::intrinsics::abort();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ abnormal termination occurred here
---



full stderr:
custom alloc error handler: Layout { size: 4, align: 4 (1 << 2) }
error: abnormal termination: the program aborted execution
##[error]  --> tests/fail/alloc/alloc_error_handler_custom.rs:19:5
   |
LL |     core::intrinsics::abort();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ abnormal termination occurred here
---



FAILED TEST: tests/fail/alloc/alloc_error_handler_no_std.rs
command: MIRI_ENV_VAR_TEST="0" MIRI_TEMP="/tmp/miri-uitest-kLghlF" RUST_BACKTRACE="1" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/release/miri" "--error-format=json" "-Dwarnings" "-Dunused" "-Ainternal_features" "-Zui-testing" "--sysroot=/checkout/obj/build/x86_64-unknown-linux-gnu/miri-sysroot" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/tmp/miri_ui/0/tests/fail/alloc" "tests/fail/alloc/alloc_error_handler_no_std.rs" "-Cpanic=abort" "--edition" "2021"

error: actual output differed from expected
Execute `./miri test --bless` to update `tests/fail/alloc/alloc_error_handler_no_std.stderr` to the actual output
--- tests/fail/alloc/alloc_error_handler_no_std.stderr
+++ <stderr output>
---
 error: abnormal termination: the program aborted execution
... 6 lines skipped ...
            0: panic_handler
                at tests/fail/alloc/alloc_error_handler_no_std.rs:LL:CC
-           1: alloc::alloc::__alloc_error_handler::__rdl_alloc_error_handler
+           1: core::alloc::__alloc_error_handler::__rdl_alloc_error_handler
+               at RUSTLIB/core/src/alloc/mod.rs:LL:CC
+           2: core::alloc::handle_alloc_error::rt_error
+               at RUSTLIB/core/src/alloc/mod.rs:LL:CC
+           3: core::alloc::handle_alloc_error
+               at RUSTLIB/core/src/alloc/mod.rs:LL:CC
---
   |
   = note: stack backtrace:
           0: panic_handler
               at tests/fail/alloc/alloc_error_handler_no_std.rs:22:5: 22:30
           1: core::alloc::__alloc_error_handler::__rdl_alloc_error_handler
               at /checkout/library/core/src/alloc/mod.rs:538:9: 541:10
           2: core::alloc::handle_alloc_error::rt_error
               at /checkout/library/core/src/alloc/mod.rs:516:13: 516:70
           3: core::alloc::handle_alloc_error
               at /checkout/library/core/src/alloc/mod.rs:522:9: 522:75
---
   |
   = note: stack backtrace:
           0: panic_handler
               at tests/fail/alloc/alloc_error_handler_no_std.rs:22:5: 22:30
           1: core::alloc::__alloc_error_handler::__rdl_alloc_error_handler
               at /checkout/library/core/src/alloc/mod.rs:538:9: 541:10
           2: core::alloc::handle_alloc_error::rt_error
               at /checkout/library/core/src/alloc/mod.rs:516:13: 516:70
           3: core::alloc::handle_alloc_error
               at /checkout/library/core/src/alloc/mod.rs:522:9: 522:75
---
Location:
   /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ui_test-0.30.7/src/lib.rs:365

  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ BACKTRACE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
   1: <color_eyre[a452ab70a1ebc890]::config::EyreHook>::into_eyre_hook::{closure#0}<unknown>
      at <unknown source file>:<unknown line>
   2: eyre[341337e102e3a7bb]::capture_handler<unknown>
      at <unknown source file>:<unknown line>
   3: eyre[341337e102e3a7bb]::private::format_err<unknown>
      at <unknown source file>:<unknown line>
   4: ui_test[f4a47f4df6b636fa]::run_tests_generic::<ui_test[f4a47f4df6b636fa]::default_file_filter, ui[912b4033f7b05550]::run_tests::{closure#1}, alloc[e0f6f22e2c747733]::boxed::Box<dyn ui_test[f4a47f4df6b636fa]::status_emitter::StatusEmitter>><unknown>
      at <unknown source file>:<unknown line>
   5: ui[912b4033f7b05550]::ui<unknown>
      at <unknown source file>:<unknown line>
   6: ui[912b4033f7b05550]::main<unknown>
      at <unknown source file>:<unknown line>
   7: std[7ef69a6b900fffa6]::sys::backtrace::__rust_begin_short_backtrace::<fn() -> core[f5b52ff5da77da03]::result::Result<(), eyre[341337e102e3a7bb]::Report>, core[f5b52ff5da77da03]::result::Result<(), eyre[341337e102e3a7bb]::Report>><unknown>
      at <unknown source file>:<unknown line>
   8: std[7ef69a6b900fffa6]::rt::lang_start::<core[f5b52ff5da77da03]::result::Result<(), eyre[341337e102e3a7bb]::Report>>::{closure#0}<unknown>
      at <unknown source file>:<unknown line>
   9: std[7ef69a6b900fffa6]::rt::lang_start_internal<unknown>
      at <unknown source file>:<unknown line>
  10: main<unknown>
      at <unknown source file>:<unknown line>
  11: __libc_start_main<unknown>
      at <unknown source file>:<unknown line>
  12: _start<unknown>
      at <unknown source file>:<unknown line>

Run with COLORBT_SHOW_HIDDEN=1 environment variable to disable frame filtering.
Run with RUST_BACKTRACE=full to include source snippets.
error: test failed, to rerun pass `--test ui`

Caused by:
  process didn't exit successfully: `/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/release/deps/ui-2814ac7bbd734e86` (exit status: 1)
Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo test --target x86_64-unknown-linux-gnu -Zbinary-dep-depinfo -j 4 -Zroot-dir=/checkout --locked --color=always --profile=release --manifest-path /checkout/src/tools/miri/Cargo.toml -- [workdir=/checkout]` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:191:21
Executed at: src/bootstrap/src/core/build_steps/test.rs:769:19

--- BACKTRACE vvv
   0: <bootstrap::utils::exec::DeferredCommand>::finish_process
             at /checkout/src/bootstrap/src/utils/exec.rs:939:17
   1: <bootstrap::utils::exec::DeferredCommand>::wait_for_output::<&bootstrap::utils::exec::ExecutionContext>
             at /checkout/src/bootstrap/src/utils/exec.rs:831:21
   2: <bootstrap::utils::exec::ExecutionContext>::run
             at /checkout/src/bootstrap/src/utils/exec.rs:741:45
   3: <bootstrap::utils::exec::BootstrapCommand>::run::<&bootstrap::core::builder::Builder>
             at /checkout/src/bootstrap/src/utils/exec.rs:339:27
   4: <bootstrap::core::build_steps::test::Miri as bootstrap::core::builder::Step>::run
             at /checkout/src/bootstrap/src/core/build_steps/test.rs:769:19
   5: <bootstrap::core::builder::Builder>::ensure::<bootstrap::core::build_steps::test::Miri>
             at /checkout/src/bootstrap/src/core/builder/mod.rs:1596:36
   6: <bootstrap::core::build_steps::test::Miri as bootstrap::core::builder::Step>::make_run
             at /checkout/src/bootstrap/src/core/build_steps/test.rs:695:21
   7: <bootstrap::core::builder::StepDescription>::maybe_run
             at /checkout/src/bootstrap/src/core/builder/mod.rs:476:13
   8: bootstrap::core::builder::cli_paths::match_paths_to_steps_and_run
             at /checkout/src/bootstrap/src/core/builder/cli_paths.rs:232:18
   9: <bootstrap::core::builder::Builder>::run_step_descriptions
             at /checkout/src/bootstrap/src/core/builder/mod.rs:1139:9
  10: <bootstrap::core::builder::Builder>::execute_cli
             at /checkout/src/bootstrap/src/core/builder/mod.rs:1118:14
  11: <bootstrap::Build>::build
             at /checkout/src/bootstrap/src/lib.rs:803:25
  12: bootstrap::main
             at /checkout/src/bootstrap/src/bin/main.rs:130:11
  13: <fn() as core::ops::function::FnOnce<()>>::call_once
             at /rustc/0417c25868d6dfbd1c291dfeae950504faa6f790/library/core/src/ops/function.rs:250:5
  14: std::sys::backtrace::__rust_begin_short_backtrace::<fn(), ()>
             at /rustc/0417c25868d6dfbd1c291dfeae950504faa6f790/library/std/src/sys/backtrace.rs:166:18
  15: std::rt::lang_start::<()>::{closure#0}
             at /rustc/0417c25868d6dfbd1c291dfeae950504faa6f790/library/std/src/rt.rs:206:18
  16: <&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe as core::ops::function::FnOnce<()>>::call_once
             at /rustc/0417c25868d6dfbd1c291dfeae950504faa6f790/library/core/src/ops/function.rs:287:21
  17: std::panicking::catch_unwind::do_call::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/0417c25868d6dfbd1c291dfeae950504faa6f790/library/std/src/panicking.rs:581:40
  18: std::panicking::catch_unwind::<i32, &dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe>
             at /rustc/0417c25868d6dfbd1c291dfeae950504faa6f790/library/std/src/panicking.rs:544:19
  19: std::panic::catch_unwind::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/0417c25868d6dfbd1c291dfeae950504faa6f790/library/std/src/panic.rs:359:14
  20: std::rt::lang_start_internal::{closure#0}
             at /rustc/0417c25868d6dfbd1c291dfeae950504faa6f790/library/std/src/rt.rs:175:24
  21: std::panicking::catch_unwind::do_call::<std::rt::lang_start_internal::{closure#0}, isize>
             at /rustc/0417c25868d6dfbd1c291dfeae950504faa6f790/library/std/src/panicking.rs:581:40
---
  28: __libc_start_main
  29: _start


Command has failed. Rerun with -v to see more details.
Bootstrap failed while executing `test --stage 2 src/tools/miri src/tools/miri/cargo-miri`
Build completed unsuccessfully in 0:47:33
  local time: Sun Jun 21 02:18:30 UTC 2026
  network time: Sun, 21 Jun 2026 02:18:30 GMT
##[error]Process completed with exit code 1.

[programmerjake]

shouldn't this be feature = "global_alloc" to match the original code?

View changes since the review

[bjorn3]

Hang on won't this break rust-for-linux and others that only use libcore and don't let rustc do the linking to generate the default implementation of alloc_error_handler? This might have to wait until EII can be used for alloc_error_handler.

[clarfonthey]

Yeah, to be clear, this would not be mergeable as-is and you're right that this would probably break things. I mostly wanted to see how many things would break.

You're right EII is probably the right solution.