Windows Julia 1.12 is blocked by Reactant jl_cstr_to_string linkage

Problem

The current Julia 1.12 Windows Core job fails before NeuralOperators tests can run because Reactant cannot link its precompile image:

lld: error: undefined symbol: jl_cstr_to_string
>>> referenced by ... Reactant ... call_with_reactant

The failing environment resolves Julia 1.12.7 and Reactant 0.2.284. Julia LTS and the non-Windows lanes pass this boundary.

This is not a NeuralOperators implementation failure: Reactant's own current workflow at commit c820cb6dd48afda4ad9d8c7d7d6b8161abc137bb reproduces it in both Julia 1.12 Windows jobs, while its Julia 1.10 and 1.11 Windows jobs pass.

Standalone dependency reproducer

The dependency-only boundary imports no SciML package:

using Pkg
Pkg.activate(; temp = true)
Pkg.add(PackageSpec(name = "Reactant", version = "0.2.284"))
using Reactant

On Julia 1.12.7 for Windows, Reactant precompilation reaches the same undefined-symbol link failure. Reactant's own Julia 1.12 Windows jobs below are the clean upstream reproductions.

Root-cause evidence

Reactant emits a direct LLVM declaration and call to "jl_cstr_to_string" in src/utils.jl. An audit of the official Julia 1.12.6 and 1.12.7 Windows import libraries shows that libjulia.dll.a provides only the import-address-table entry for that name, while libjulia-internal.dll.a provides the directly callable ijl_cstr_to_string symbol:

1.12.6/libjulia.dll.a:          I __imp_jl_cstr_to_string
1.12.6/libjulia-internal.dll.a: I __imp_ijl_cstr_to_string
1.12.6/libjulia-internal.dll.a: T ijl_cstr_to_string
1.12.7/libjulia.dll.a:          I __imp_jl_cstr_to_string
1.12.7/libjulia-internal.dll.a: I __imp_ijl_cstr_to_string
1.12.7/libjulia-internal.dll.a: T ijl_cstr_to_string

That makes an upstream correction to the emitted symbol (ijl_cstr_to_string) or to its Windows DLL-import declaration the likely repair. This is an inference from the import libraries and Reactant source; it has not yet been validated by a Reactant patch on Windows.

Chris is not an owner, maintainer, or top contributor in EnzymeAD/Reactant.jl, so no upstream issue or PR will be opened without explicit permission. This SciML issue tracks the blocked NeuralOperators lane in the meantime. A NeuralOperators-side version pin, test exclusion, or platform gate would only hide the dependency regression and is not proposed.

Links

• NeuralOperators failing job: https://github.com/SciML/NeuralOperators.jl/actions/runs/33313226757/job/99312377020
• Reactant Julia 1.12 Windows integration failure: https://github.com/EnzymeAD/Reactant.jl/actions/runs/33429642165/job/99676131381
• Reactant Julia 1.12 Windows core failure: https://github.com/EnzymeAD/Reactant.jl/actions/runs/33429642165/job/99676131758
• Reactant source emitting the direct call: https://github.com/EnzymeAD/Reactant.jl/blob/c820cb6dd48afda4ad9d8c7d7d6b8161abc137bb/src/utils.jl#L1057-L1064

Start with the standalone Julia 1.12.7 Windows reproducer, then inspect Reactant's src/utils.jl at lines 1057-1064 and the linked Reactant workflow failures. Done means an upstream-compatible correction is validated on the affected Windows jobs and the NeuralOperators Core lane can proceed without a version pin, exclusion, or platform gate.