test(c-backend): every C syntax check asks cc which flags it takes (Closes #5907) - #5930
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…loses #5907) The bootstrap C tests passed clang's -ferror-limit=0 to whatever `cc` was. On CI that is gcc, which refuses the whole command line. Tests that grep stderr for "error" went red (23 on master); tests that count file:line:col errors went green having compiled nothing. - tests/common/mod.rs: get_cc_args() probes -ferror-limit=0, then -fmax-errors=0, and accepts a flag only on exit 0 with empty stderr. cc_check() panics when cc exits non-zero without naming a line of the file. error_count() also counts `fatal error:` lines. - 17 c_*.rs files go through `mod common;` and common::cc_check. - c_static_array_params: compile with -c, where gcc reports a short [static N] argument, and ask cc which warning tag that gets rather than demanding clang's -Warray-bounds. gcc 15 as cc, 21 affected targets: 25 failed before, 1 after (icarus_lowerable, #5910, not C). Apple clang: 2 -> 1. Part of #5906 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Closes #5907
Part of #5906
Defect
Bootstrap Test Ratchetis red on master (5432ded): 24 tests are newly failing againstscripts/ci/test-baseline.txt. 23 of them are C-backend tests. Fifteenbootstrap/tests/c_*.rsfiles hand-copied clang's-ferror-limit=0. CI'sccis gcc, which refuses the whole command line:That refusal broke the two assertion shapes in opposite directions:
!stderr.contains("error")went red, because the refusal contains the word "error". That gives the 23 failures.file:line:col: error:lines went green having compiled nothing, because the refusal has no line:col (9 files).common::get_cc_args()(1acab84) was written for this, but no test used it. It also did not compile, and its probe wrote-.ointo the cwd.Change
bootstrap/tests/common/mod.rs(rewritten):get_cc_args()probes-ferror-limit=0, then-fmax-errors=0. It accepts a flag only on exit 0 with empty stderr: Apple clang takes-fmax-errors=0with "argument unused" and exit 0.cc_check(path, extra)panics ifccexits non-zero without naming afile:line:colerror. That case isccrefusing its command line, not a reading of the header.error_count()also countsfatal error:lines (e.g. a missing#include).c_*.rsfiles usemod common;+common::cc_check.git grep ferror-limit -- bootstrap/testsnow names onlycommon/mod.rs.c_static_array_params.rs:-c, not-fsyntax-only. gcc reports a short[static N]argument in a later pass: measured on gcc 15,-fsyntax-onlyprints nothing and-cprints[-Wstringop-overflow=].-Warray-bounds. It asksccwhich tag a short argument gets in hand-written C: the tags a 2-element caller provokes minus the tags a 4-element control provokes.Unchanged on purpose: the build-and-run
cccalls inbackend_behaviour.rsandc_struct_array_fields.rs. They compile to a binary with-std=gnu11/-std=c11 -o, not syntax-check.Evidence
The 21 affected targets (18
c_*+corpus_unresolved,icarus_lowerable,backend_behaviour; 489 tests) were run locally on macOS.ccwas a shim to Homebrew gcc 15.2, then Apple clang, then Homebrew LLVM clang 21.1.8.c_auto_type_array_literal3,c_enum_member_access3,c_enum_path_members1,c_literal_list_type8,c_module_array_consts4,c_static_array_params1,c_tuple_positions3;corpus_unresolved1, since fixed on master by test(corpus): reach PID-qualified artifact write failures #5909;icarus_lowerable::corpus_classifier_matches_lean_completeness.icarus_lowerabletest. It is tracked in Restore Lean completeness agreement for phi_rope and sacred_attention #5910 and is not C.cc,backend_behaviourwas not run: rustc's link step through Homebrew clang hung in Xcodeld. That file is unchanged here.Negative control (not committed)
A temporary test in
c_abs_generic.rsgenerated a header and appendedint t27_negative_control = ;, then assertederrors()counts >= 1. It was removed before commit.Before, with gcc as
cc, the count-shaped checker was blind:(Apple clang:
ok.)After, with gcc, Apple clang and LLVM clang 21, every compiler catches it:
Ratchet
Run locally against the master CI log (run 37181879942, prefixes stripped):
The full
cargo test -p t27c --no-fail-fastunder gcc was not run locally: the shared disk was under the 3 GiB stop line. This PR's ownBootstrap Test Ratchetrun is that comparison. If that run shows only #5910 failing, I will regeneratetest-baseline.txtfrom its log with--emit-baselineand push that as a follow-up commit here, with the reason stated. All 177 current baseline rows pass on master.CI's gcc is older than 15. Whether it warns on a short
[static 4]argument at-O0 -cis read from this PR's run, not assumed. If it does not, the test fails with "this cc warns about no too-short [static 4] argument even in hand-written C" rather than passing vacuously.🤖 Generated with Claude Code