Guard AllocCheck static check against Julia-prerelease false positives#87
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ChrisRackauckas merged 1 commit intoJun 21, 2026
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The AllocCheck "Zero Allocations" testset was erroring only on the
`julia pre` (1.13.0-rc1) macOS/aarch64 CI job. AllocCheck's static
LLVM-IR analysis is explicitly documented as not guaranteed stable
across Julia versions, and the in-flux 1.13 prerelease codegen makes it
emit architecture-dependent false positives: on aarch64 it flagged even
`procf` (pure scalar Float64 arithmetic returning an `NTuple{4,Float64}`,
which cannot heap-allocate) as allocating, while x86_64 reported zero.
Runtime `@allocated` is 0 for every function on 1.13.0-rc1, confirming
there is no real allocation.
Restructure the testset so the ground-truth runtime `@allocated == 0`
assertion runs on every Julia version and architecture (a strictly
stronger regression guard than before), and additionally run AllocCheck's
static `check_allocs` only on released Julia, where its result is reliable.
No test is skipped or weakened: the static guard still runs and passes on
lts/release across all OSes, catching real allocation regressions.
Verified locally:
- 1.13.0-rc1: 10/10 pass (runtime guard; static gated off)
- 1.12.6: 20/20 pass (runtime + static)
- 1.10.11: 20/20 pass (runtime + static)
- full Core group passes on 1.13.0-rc1
Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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The
tests / Core (julia pre, macos-latest)job (Julia 1.13.0-rc1, aarch64) was the only failing check onmaster. It failed inside the AllocCheck "Zero Allocations" testset.Root cause
AllocCheck performs static LLVM-IR analysis and its docs explicitly state the result is not guaranteed stable across Julia invocations. On the in-flux Julia 1.13 prerelease codegen it emits architecture-dependent false positives: on aarch64 it flagged even
procf— pure scalarFloat64arithmetic returning anNTuple{4,Float64}, which cannot heap-allocate — as allocating, while x86_64 (ubuntu/windowspre) reported zero. Stable Julia (lts/release) passes everywhere.I confirmed with the runtime ground truth:
@allocatedis 0 forcount_rand,ad_rand,procf, andpois_randon 1.13.0-rc1. There is no real allocation — the package code is correct.Fix
Restructure
test/alloc_tests.jlso:@allocated == 0assertion (ground truth, reliable on every version/architecture) runs always — a strictly stronger regression guard than before.check_allocsruns only on released Julia (isempty(VERSION.prerelease)), where its result is reliable.No test is skipped, deleted, weakened, or tolerance-loosened. The static guard still runs and passes on lts/release across all OSes, so real allocation regressions are still caught; on prereleases the unreliable static analyzer is replaced by the reliable runtime check.
Local verification
1.13.0-rc1: 10/10 pass (runtime guard; static gated off)1.12.6: 20/20 pass (runtime + static)1.10.11: 20/20 pass (runtime + static)Coregroup passes on1.13.0-rc1Please ignore until reviewed by @ChrisRackauckas