### Analysis After #160535 we saw a regression in `tests/ui/match/match-stack-overflow-72933-.rs` on `s390x` targets. It seems that the default stack-size of 16MB is not enough for this test on s390x. This highlights actually multiple problems: * the default stack size of 16MB on s390x is not enough. -> I will create a PR and set it so the test wont fail any more. * IMHO `RUST_MIN_STACK` is misleading. This variable actually `fixes` the stack size to at least this value but will **not** allow growth beyond *(as there is no `RUST_MAX_STACK` i understood its meaning very fast)*. * increasing the stack size with `ulimit -s` did not help. this was surprising, but i guess it makes sense that the compiler will not take such value from the OS but rely on proven *good* defaults. ### Links * #160535 * #160275 * rust-lang/compiler-team#1011 ### Code https://github.com/rust-lang/rust/blob/26747db4f50d83f3670834410ac16fbd39c14c15/tests/ui/match/match-stack-overflow-72933-.rs#L1-L5209 ### Meta `rustc --version --verbose`: current `HEAD` ``` rustc 1.97.0-nightly (66da6cae1 2026-04-20) binary: rustc commit-hash: 66da6cae1a6f12e9585493ab8f8f19cf753091fd commit-date: 2026-04-20 host: s390x-unknown-linux-gnu release: 1.97.0-nightly LLVM version: 22.1.2 ``` ### Error output ``` Building test helpers for s390x-unknown-linux-gnu Testing stage1 with compiletest suite=ui mode=ui (s390x-unknown-linux-gnu) running 1 tests [ui] tests/ui/match/match-stack-overflow-72933-.rs ... F failures: ---- [ui] tests/ui/match/match-stack-overflow-72933-.rs stdout ---- error: test compilation failed although it shouldn't! status: signal: 11 (SIGSEGV) (core dumped) command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1/bin/rustc" "/home3/eddy/src/rust/tests/ui/match/match-stack-overflow-72933-.rs" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore -directory-in-diagnostics-source-blocks=/home/eddy/.cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/home3/eddy/src/rust/vendor" "--sysroot" "/home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1" "--target=s390x-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" "-C" "prefer-dynamic" "--out-dir" "/home3/eddy/src/rust/build/s390x-unknown-linux-gnu/test/ui/match/match-stack-overflow-72933-" "-Znext-solver=coherence" "-A" "unused" "-W" "unused_attributes " "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/home3/eddy/src/rust/build/s390x-unknown-linux-gnu/native/rust-test-helpers" stdout: none --- stderr ------------------------------- error: rustc interrupted by SIGSEGV, printing backtrace /home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1/lib/librustc_driver-bf213c6416d65d01.so(+0xee4fee) [0x3ffaa3e4fee] linux-vdso.so.1(__kernel_sigreturn+0x0) [0x3ffca6fe4d8] /home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1/lib/librustc_driver-bf213c6416d65d01.so(+0x65018ee) [0x3ffafa018ee] /home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1/lib/librustc_driver-bf213c6416d65d01.so(+0x651dec0) [0x3ffafa1dec0] ### cycle encountered after 4 frames with period 5 /home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1/lib/librustc_driver-bf213c6416d65d01.so(+0x651db80) [0x3ffafa1db80] /home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1/lib/librustc_driver-bf213c6416d65d01.so(+0x644030e) [0x3ffaf94030e] /home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1/lib/librustc_driver-bf213c6416d65d01.so(+0x657775c) [0x3ffafa7775c] /home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1/lib/librustc_driver-bf213c6416d65d01.so(+0x651a948) [0x3ffafa1a948] /home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1/lib/librustc_driver-bf213c6416d65d01.so(+0x651de6e) [0x3ffafa1de6e] ### recursed 50 times /home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1/lib/librustc_driver-bf213c6416d65d01.so(+0x651db80) [0x3ffafa1db80] /home3/eddy/src/rust/build/s390x-unknown-linux-gnu/stage1/lib/librustc_driver-bf213c6416d65d01.so(+0x644030e) [0x3ffaf94030e] note: rustc unexpectedly overflowed its stack! this is a bug note: maximum backtrace depth reached, frames may have been lost note: we would appreciate a report at https://github.com/rust-lang/rust help: you can increase rustc's stack size by setting RUST_MIN_STACK=33554432 ------------------------------------------ ---- [ui] tests/ui/match/match-stack-overflow-72933-.rs stdout end ---- failures: [ui] tests/ui/match/match-stack-overflow-72933-.rs test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 22106 filtered out; finished in 1.54s Some tests failed in compiletest suite=ui mode=ui host=s390x-unknown-linux-gnu target=s390x-unknown-linux-gnu Build completed unsuccessfully in 0:00:02 ```