Increase the default stack size to 16 MiB and remove `ensure_sufficient_stack` - #160535

ChrisDenton · 2026-08-05T01:05:33Z

View all comments

Tracking issue: #160275

Fixes #93237
Fixes #108499

rustbot · 2026-08-05T01:05:36Z

Some changes occurred in match checking

cc @Nadrieril

Some changes occurred in match lowering

cc @Nadrieril

changes to the core type system

cc @lcnr

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

The parser was modified, potentially altering the grammar of (stable) Rust
which would be a breaking change.

cc @fmease

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

Some changes occurred in exhaustiveness checking

cc @Nadrieril

rustbot · 2026-08-05T01:05:38Z

r? @petrochenkov

rustbot has assigned @petrochenkov.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

Owners of files modified in this PR: compiler, types
compiler, types expanded to 75 candidates
Random selection from 20 candidates

ChrisDenton · 2026-08-05T01:08:59Z

Oh that pinged everyone, sorry. It does touch a lot of files but most of the +/- diff is whitespace changes.

rustbot · 2026-08-05T01:30:08Z

The list of allowed third-party dependencies may have been modified! You must ensure that any new dependencies have compatible licenses before merging.

cc @davidtwco, @BoxyUwU

ChrisDenton · 2026-08-05T03:10:41Z

This test is fairly recent but I'm not sure that this it is still useful. It's basically testing the use of stacker, which is obsolete now.

View changes since the review

I suspect that this test might start failing again with increased scale of the test (e.g. if N=8000 fails at 3MiB, then at N=45000 it would fail at 16MiB.) But maybe making the scale here large enough makes the code itself impractical in other ways? 🤷

One thing I'm finding with these high recursion cases is that they start becoming very slow even before they approach the (new) stack limit. So we could increase the stack size further if there's a real world use case (which I don't see atm but not ruling out) but I think that might be sweeping the problem under the rug. I do feel that at the very least we should be warning about it if not treating it as a bug to be fixed.

bjorn3 · 2026-08-05T11:25:24Z

-    "windows_i686_msvc",
-    "windows_x86_64_gnu",
-    "windows_x86_64_gnullvm",
-    "windows_x86_64_msvc",


❤️ Helps with #156459

View changes since the review

rustbot · 2026-08-05T11:55:48Z

This PR changes a file inside tests/crashes. If a crash was fixed, please move into the corresponding ui subdir and add 'Fixes #' to the PR description to autoclose the issue upon merge.

petrochenkov · 2026-08-05T12:00:21Z

The implementation looks good to me.

Do you think this needs a whole team FCP in addition to the seconded MCP?
If not then r=me when CI is green.
@rustbot author
@bors rollup=never

ChrisDenton · 2026-08-08T23:00:09Z

@bors try jobs=i686-gnu-nopt-1

…=<try> Increase the default stack size to 16 MiB and remove `ensure_sufficient_stack` try-job: i686-gnu-nopt-1

ChrisDenton · 2026-08-08T23:27:38Z

@bors try jobs=various,i686,arm,apple,android

…=<try> Increase the default stack size to 16 MiB and remove `ensure_sufficient_stack` try-job: *various* try-job: *i686* try-job: *arm* try-job: *apple* try-job: *android*

rust-bors · 2026-08-08T23:28:21Z

💔 Test for 271f298 failed: CI. Failed job:

Calculate job matrix (web logs, enhanced plaintext logs)

ChrisDenton · 2026-08-08T23:30:48Z

@bors try jobs=various,i686*,arm,android

…=<try> Increase the default stack size to 16 MiB and remove `ensure_sufficient_stack` try-job: *various* try-job: i686* try-job: *arm* try-job: *android*

On 32-bit systems, 255 threads will use up the available address space.

ChrisDenton · 2026-08-08T23:36:09Z

@bors try jobs=various,i686*,arm,android

…=<try> Increase the default stack size to 16 MiB and remove `ensure_sufficient_stack` try-job: *various* try-job: i686* try-job: *arm* try-job: *android*

rust-bors · 2026-08-09T02:38:53Z

☀️ Try build successful (CI)
Build commit: 1013c3d (1013c3d66934aafd2123d3d36976c7bf7505f441)
Base parent: 771916f (771916f9028e7fe56d2685f2c4f698de5d7d6a45)

ChrisDenton · 2026-08-09T02:38:58Z

Ok, I think I tested all the 32-bit runners so hopefully there are no more surprises.

@bors r=petrochenkov,oli-obk

rust-bors · 2026-08-09T02:39:01Z

📌 Commit 12d204f has been approved by petrochenkov,oli-obk

It is now in the queue for this repository.

…=petrochenkov,oli-obk Increase the default stack size to 16 MiB and remove `ensure_sufficient_stack` Tracking issue: #160275 Fixes #93237 Fixes #108499

rust-log-analyzer · 2026-08-09T03:56:09Z

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

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

46 
+ error[E0658]: macro attributes on statements are unstable
+   --> $DIR/autodiff_illegal.rs:49:5
+    |
+ LL |     #[autodiff_forward(df7, Dual)]
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    |
+    = note: see issue #54727 <https://github.com/rust-lang/rust/issues/54727> for more information
+    = help: add `#![feature(proc_macro_hygiene)]` to the crate attributes to enable
+    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+ 
47 error: autodiff must be applied to function
48   --> $DIR/autodiff_illegal.rs:50:5
49    |

50 LL |     let mut x = 5;
51    |     ^^^^^^^^^^^^^^
52 
+ error[E0658]: macro attributes on expressions are unstable
+   --> $DIR/autodiff_illegal.rs:53:5
+    |
+ LL |     #[autodiff_forward(df7, Dual)]
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    |
+    = note: see issue #54727 <https://github.com/rust-lang/rust/issues/54727> for more information
+    = help: add `#![feature(proc_macro_hygiene)]` to the crate attributes to enable
+    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+ 
53 error: autodiff must be applied to function
54   --> $DIR/autodiff_illegal.rs:54:5
55    |

56 LL |     x = x + 3;
57    |     ^
58 
+ error[E0658]: macro attributes on statements are unstable
+   --> $DIR/autodiff_illegal.rs:58:5
+    |
+ LL |     #[autodiff_forward(df7, Dual)]
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    |
+    = note: see issue #54727 <https://github.com/rust-lang/rust/issues/54727> for more information
+    = help: add `#![feature(proc_macro_hygiene)]` to the crate attributes to enable
+    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+ 
59 error: autodiff must be applied to function
60   --> $DIR/autodiff_illegal.rs:59:5
61    |

124 LL | #[autodiff_reverse(df21, Active, Duplicated)]
125    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
126 
- error: aborting due to 18 previous errors
+ error: aborting due to 21 previous errors
128 
---
-   --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:58:5
+ error[E0658]: macro attributes on statements are unstable
+   --> $DIR/autodiff_illegal.rs:49:5
+    |
+ LL |     #[autodiff_forward(df7, Dual)]
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    |
+    = note: see issue #54727 <https://github.com/rust-lang/rust/issues/54727> for more information
+    = help: add `#![feature(proc_macro_hygiene)]` to the crate attributes to enable
+    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+ 
+ error[E0658]: macro attributes on expressions are unstable
+   --> $DIR/autodiff_illegal.rs:53:5
+    |
+ LL |     #[autodiff_forward(df7, Dual)]
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    |
+    = note: see issue #54727 <https://github.com/rust-lang/rust/issues/54727> for more information
+    = help: add `#![feature(proc_macro_hygiene)]` to the crate attributes to enable
+    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+ 
+ error[E0658]: macro attributes on statements are unstable
+   --> $DIR/autodiff_illegal.rs:58:5
+    |
+ LL |     #[autodiff_forward(df7, Dual)]
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    |
+    = note: see issue #54727 <https://github.com/rust-lang/rust/issues/54727> for more information
+    = help: add `#![feature(proc_macro_hygiene)]` to the crate attributes to enable
+    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+ 
+ error: aborting due to 21 previous errors


The actual stderr differed from the expected stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args autodiff/autodiff_illegal.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/autodiff/autodiff_illegal.rs" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--target=x86_64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/autodiff/autodiff_illegal" "-A" "unused" "-W" "unused_attributes" "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers"
stdout: none
--- stderr -------------------------------
error[E0658]: attributes on expressions are experimental
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:53:5
   |
LL |     #[autodiff_forward(df7, Dual)]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
   = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: Duplicated can not be used for this type
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:14:14
   |
LL | pub fn f1(x: f64) {
---

error: Dual can not be used in Reverse Mode
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:34:1
   |
LL | #[autodiff_reverse(df5, Dual)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: Duplicated can not be used in Forward Mode
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:41:1
   |
---

error[E0658]: macro attributes on statements are unstable
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:49:5
   |
LL |     #[autodiff_forward(df7, Dual)]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #54727 <https://github.com/rust-lang/rust/issues/54727> for more information
   = help: add `#![feature(proc_macro_hygiene)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: autodiff must be applied to function
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:50:5
   |
LL |     let mut x = 5;
   |     ^^^^^^^^^^^^^^

error[E0658]: macro attributes on expressions are unstable
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:53:5
   |
LL |     #[autodiff_forward(df7, Dual)]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #54727 <https://github.com/rust-lang/rust/issues/54727> for more information
   = help: add `#![feature(proc_macro_hygiene)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: autodiff must be applied to function
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:54:5
   |
LL |     x = x + 3;
   |     ^

error[E0658]: macro attributes on statements are unstable
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:58:5
   |
LL |     #[autodiff_forward(df7, Dual)]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #54727 <https://github.com/rust-lang/rust/issues/54727> for more information
   = help: add `#![feature(proc_macro_hygiene)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: autodiff must be applied to function
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:59:5
   |
LL |     let add_one_v2 = |x: u32| -> u32 { x + 1 };
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: autodiff requires at least a name and mode
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:65:1
   |
---
   |
LL | fn fn_exists() {}
   | -------------- previous definition of the value `fn_exists` here
...
LL | #[autodiff_reverse(fn_exists, Active)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `fn_exists` redefined here
   |
   = note: `fn_exists` must be defined only once in the value namespace of this module

error: did not recognize Activity: `Reverse`
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:95:26
   |
LL | #[autodiff_reverse(df13, Reverse)]
   |                          ^^^^^^^

error: invalid return activity Active in Forward Mode
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:131:1
   |
LL | #[autodiff_forward(df19, Dual, Active)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: invalid return activity Dual in Reverse Mode
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:137:1
   |
LL | #[autodiff_reverse(df20, Active, Dual)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: invalid return activity Duplicated in Reverse Mode
##[error]  --> /checkout/tests/ui/autodiff/autodiff_illegal.rs:144:1
   |
LL | #[autodiff_reverse(df21, Active, Duplicated)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 21 previous errors

Some errors have detailed explanations: E0428, E0658.
---
[TIMING:end] test::Ui { test_compiler: Compiler { stage: 2, host: x86_64-unknown-linux-gnu, forced_compiler: false }, target: x86_64-unknown-linux-gnu } -- 0.000

1 command(s) did not execute successfully:

  - env -u CARGO DOC_RUST_LANG_ORG_CHANNEL="https://doc.rust-lang.org/nightly" LD_LIBRARY_PATH="" RUSTC="/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/rustc" RUSTC_BOOTSTRAP="1" RUSTC_FORCE_RUSTC_VERSION="compiletest" RUST_TEST_THREADS="4" RUST_TEST_TMPDIR="/checkout/obj/build/tmp" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage1-tools-bin/compiletest" "--stage" "2" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--minicore-path" "/checkout/tests/auxiliary/minicore.rs" "--src-root" "/checkout" "--src-test-suite-root" "/checkout/tests/ui" "--build-root" "/checkout/obj/build" "--build-test-suite-root" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--sysroot-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--suite" "ui" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/checkout/obj/build/x86_64-unknown-linux-gnu/llvm/build/bin/FileCheck" "--default-codegen-backend" "llvm" "--has-enzyme" "--optimize-tests" "--host-rustcflags" "-Crpath" "--host-rustcflags" "-Cdebuginfo=0" "--host-rustcflags" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath" "--target-rustcflags" "-Cdebuginfo=0" "--target-rustcflags" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--python" "/usr/bin/python3" "autodiff" "feature-gates/feature-gate-autodiff.rs" "--verbose-run-make-subprocess-output" "--with-rustc-debug-assertions" "--with-std-debug-assertions" "--jobs" "4" "--llvm-version" "23.1.0-rust-1.99.0-nightly" "--llvm-components" "aarch64 aarch64asmparser aarch64codegen aarch64desc aarch64disassembler aarch64info aarch64utils abi aggressiveinstcombine all all-targets amdgpu amdgpuasmparser amdgpucodegen amdgpudesc amdgpudisassembler amdgpuinfo amdgputargetmca amdgpuutils analysis arm armasmparser armcodegen armdesc armdisassembler arminfo armutils asmparser asmprinter avr avrasmparser avrcodegen avrdesc avrdisassembler avrinfo binaryformat bitreader bitstreamreader bitwriter bpf bpfasmparser bpfcodegen bpfdesc bpfdisassembler bpfinfo cas cfguard cgdata codegen codegentypes core coroutines coverage csky cskyasmparser cskycodegen cskydesc cskydisassembler cskyinfo debuginfobtf debuginfocodeview debuginfodwarf debuginfodwarflowlevel debuginfogsym debuginfologicalview debuginfomsf debuginfopdb demangle dlltooldriver dtlto dwarfcfichecker dwarflinker dwarflinkerclassic dwarflinkerparallel dwp engine executionengine extensions filecheck frontendatomic frontenddirective frontenddriver frontendhlsl frontendoffloading frontendopenacc frontendopenmp fuzzercli fuzzmutate globalisel hexagon hexagonasmparser hexagoncodegen hexagondesc hexagondisassembler hexagoninfo hipstdpar instcombine instrumentation interfacestub interpreter ipo irprinter irreader jitlink libdriver lineeditor linker loongarch loongarchasmparser loongarchcodegen loongarchdesc loongarchdisassembler loongarchinfo lto m68k m68kasmparser m68kcodegen m68kdesc m68kdisassembler m68kinfo mc mca mcdisassembler mcjit mcparser mips mipsasmparser mipscodegen mipsdesc mipsdisassembler mipsinfo mirparser msp430 msp430asmparser msp430codegen msp430desc msp430disassembler msp430info native nativecodegen nvptx nvptxcodegen nvptxdesc nvptxinfo objcarcopts objcopy object objectyaml option orcdebugging orcjit orcshared orctargetprocess passes plugins powerpc powerpcasmparser powerpccodegen powerpcdesc powerpcdisassembler powerpcinfo profiledata remarks riscv riscvasmparser riscvcodegen riscvdesc riscvdisassembler riscvinfo riscvtargetmca runtimedyld sandboxir scalaropts selectiondag sparc sparcasmparser sparccodegen sparcdesc sparcdisassembler sparcinfo support supportlsp symbolize systemz systemzasmparser systemzcodegen systemzdesc systemzdisassembler systemzinfo tablegen target targetparser telemetry textapi textapibinaryreader transformutils vectorize webassembly webassemblyasmparser webassemblycodegen webassemblydesc webassemblydisassembler webassemblyinfo webassemblyutils windowsdriver windowsmanifest x86 x86asmparser x86codegen x86desc x86disassembler x86info x86targetmca xray xtensa xtensaasmparser xtensacodegen xtensadesc xtensadisassembler xtensainfo" "--cc" "" "--cxx" "" "--cflags" "" "--cxxflags" "" "--channel" "nightly" "--git-hash" "--nightly-branch" "main" "--git-merge-commit-email" "bors@rust-lang.org" (failure_mode=Exit)
Bootstrap failed while executing `test --stage 2 --no-fail-fast tests/codegen-llvm/autodiff tests/pretty/autodiff tests/ui/autodiff tests/ui/feature-gates/feature-gate-autodiff.rs`
Currently active steps:
Build completed unsuccessfully in 0:53:14
  local time: Sun Aug  9 03:55:56 UTC 2026
  network time: Sun, 09 Aug 2026 03:55:56 GMT

Important

For more information how to resolve CI failures of this job, visit this link.

rust-bors · 2026-08-09T05:15:14Z

💔 Test for 9791cec failed: CI. Failed jobs:

auto - dist-aarch64-linux (web logs, enhanced plaintext logs)
auto - optional-x86_64-gnu-autodiff (web logs, enhanced plaintext logs)

rustbot assigned petrochenkov Aug 5, 2026

ChrisDenton changed the title ~~Remove ensure sufficient stack~~ Increase the stack size to 16 MiB and remove ensure sufficient stack Aug 5, 2026

ChrisDenton changed the title ~~Increase the stack size to 16 MiB and remove ensure sufficient stack~~ Increase the default stack size to 16 MiB and remove ensure sufficient stack Aug 5, 2026

ChrisDenton changed the title ~~Increase the default stack size to 16 MiB and remove ensure sufficient stack~~ Increase the default stack size to 16 MiB and remove ensure_sufficient_stack Aug 5, 2026