## Motivation
The orcjit addon links against conda-forge's LLVM, which is built with a newer
GCC whose libstdc++ carries `GLIBCXX_3.4.29+` symbols. Those exceed the
`manylinux_2_28` floor this project standardized on in #675, which is why the
addon has carried a `-static-libstdc++`/`-static-libgcc` workaround since the
original addon PR (#254).
This builds LLVM from source inside the `manylinux_2_28` image instead,
publishes the install prefix as a release asset, and has CI download it.
Because that toolchain already sits at the manylinux ABI floor, the workaround
is no longer needed.
## What changes
* **LLVM acquisition (Linux).** `/opt/llvm` is obtained by downloading
`llvm-<version>-linux-<arch>.tar.zst` and extracting it, instead of being built
or installed via conda. macOS/Windows keep the conda-forge binaries (no GLIBCXX
floor); their `actions/cache` step is split out so their install gating is
unchanged. Everything downstream is untouched — same `/opt/llvm`, same
`LLVM_PREFIX`, same bind-mount into the build container.
* **Drop `-static-libstdc++`/`-static-libgcc`,** so the addon no longer bakes
in a private copy of the C++ runtime.
* **Add an explicit ABI assertion.** auditwheel does *not* fail on a too-new
symbol — it silently selects a laxer tag, so a regression to `GLIBCXX_3.4.30`
would still produce a valid `manylinux_2_35` wheel and pass CI unnoticed. The
new step fails unless every wheel is tagged `manylinux_2_28` or lower, and logs
the highest `GLIBCXX`/`CXXABI` versions imported.
The by-name `--exclude-libs` list is deliberately **kept** rather than
collapsed to `--exclude-libs,ALL`. I tried that; it fails. The embedded
`liborc_rt.a` is linked by the JIT at run time and resolves its C++ runtime
through the process, including archive-only helpers such as
`_ZSt28__throw_bad_array_new_lengthv` that `libstdc++.so` does not export —
`ALL` localizes those and the ORC platform fails to materialize (`Failed to
materialize symbols: { (<Platform>, ...) }`). That holds whether libstdc++ is
static or dynamic, so the comment there is corrected rather than the flag
changed.
## Results
Full CI green on all four platforms. Both Linux legs now report:
```
max GLIBCXX imported: GLIBCXX_3.4.22
max CXXABI imported: CXXABI_1.3.11
C++ runtime refs (expect UND -> served by the process libstdc++):
_Znwm@GLIBCXX_3.4
__cxa_throw@CXXABI_1.3
__gxx_personality_v0@CXXABI_1.3
defined dynamic exports: 30 (x86_64; 29 on aarch64)
```
That is exactly the documented floor, and dynamic exports drop from ~965 to ~30
— the addon no longer re-exports a private libstdc++, removing the
interposition hazard with a host's own copy (e.g. PyTorch's bundled LLVM).
Tests: 89 passed x86_64 / 87 passed aarch64, plus the quick-start C and C++
examples.
Prebuilt LLVM is produced out-of-band, so this also removes a ~50 minute
from-source build from the CI path; the Linux orcjit jobs now spend a few
minutes downloading.
## Notes for reviewers
Two things worth flagging that are not visible in the diff:
1. **Artifact provenance.** Linux LLVM now comes from a release asset in
`mlc-ai/package`, which is outside the ASF org. The asset is currently a
**pre-release**, and the workflow that produces it lives on an unmerged branch
there. That side should land (and ideally be promoted out of pre-release)
before this is merged — hence the draft status. The download source is
parameterized via the `llvm_release_repo` input if you would prefer it mirrored
elsewhere.
2. **`publish_orcjit_wheel.yml` inherits this.** It calls the same composite
action without passing `llvm_version`/`llvm_release_repo`, so published PyPI
wheels will also start sourcing LLVM from that release. This is a supply-chain
change to a published artifact that the diff does not visibly touch.
Builds on #675 (`manylinux_2_28` standardization), which is what makes the
floor the right target.
You can view, comment on, or merge this pull request online at:
https://github.com/apache/tvm-ffi/pull/688
-- Commit Summary --
* [CI][ORCJIT] Source manylinux LLVM from a release, link libstdc++
dynamically
-- File Changes --
M .github/actions/build-orcjit-wheel/action.yml (118)
M .github/workflows/ci_test.yml (13)
M addons/tvm_ffi_orcjit/CMakeLists.txt (17)
-- Patch Links --
https://github.com/apache/tvm-ffi/pull/688.patch
https://github.com/apache/tvm-ffi/pull/688.diff
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