Case 82: SYCL overload set removed (DPC++ build withdrawn)¶

Field	Value
Verdict	🔴 BREAKING
Category	Breaking
Platforms	Linux, macOS, Windows
Flags	ABI break, API break
Detected `ChangeKind`s	`sycl_overload_set_removed`
Source files	`examples/case82_sycl_overload_set_removed/`

Category: Overload-family ABI | Verdict: BREAKING

What breaks¶

In v1 the library exports every algorithm entry point twice — once with a CPU signature and once accepting sycl::queue& as the first parameter:

result_t compute(const descriptor&, const table&);
result_t compute(sycl::queue&, const descriptor&, const table&);   // SYCL

In v2 the DPC++ build is dropped. The CPU overloads are unchanged; the sycl::queue& overloads disappear — typically 30–80 symbols across an algorithm catalog like oneDAL's.

Mechanically this is N×func_removed. Reporting it that way buries the signal under a wall of independent removals, making the suppression UX a mess (one rule per algorithm) and obscuring the deployment-level question ("did the SYCL surface go away?").

Real Failure Demo¶

Severity: BREAKING / LOAD-TIME FAILURE

cmake -S examples -B /tmp/abicheck-examples-build -DCMAKE_BUILD_TYPE=Debug
cmake --build /tmp/abicheck-examples-build --target case82_sycl_overload_set_removed_app case82_sycl_overload_set_removed_v2

tmp=$(mktemp -d)
cp /tmp/abicheck-examples-build/case82_sycl_overload_set_removed/app_v1 "$tmp/"
cp /tmp/abicheck-examples-build/case82_sycl_overload_set_removed/libv2.so "$tmp/libv1.so"
(cd "$tmp" && LD_LIBRARY_PATH=. ./app_v1)
# ./app_v1: symbol lookup error: undefined symbol: _ZN5mylib7computeERN4sycl5queueERKNS_10descriptorERKNS_5tableE

Why this is its own ChangeKind¶

A grouped finding — SYCL_OVERLOAD_SET_REMOVED — names the deployment event in one place: "the DPC++ overload family was removed (N affected entry points: compute, train, infer, finalize, …)". Per-symbol func_removed findings for the affected entries are suppressed as children.

How abicheck detects it¶

After the per-symbol removal pass, the new detector (abicheck/diff_cpp_patterns.py::detect_sycl_overload_set_removal) groups removed symbols by their demangled unqualified name and parameter list-minus-first-arg. When ≥ K removed siblings share an unqualified name with a surviving non-SYCL overload AND the removed one's first parameter type contains sycl::queue, a single SYCL_OVERLOAD_SET_REMOVED finding is emitted listing the affected entry-point family.

Real-world reference¶

cpp/oneapi/dal/algo/*/compute.hpp, train.hpp, infer.hpp each ship a CPU overload and a sycl::queue& overload guarded by ONEDAL_DATA_PARALLEL. Switching off DPC++ at build time withdraws every queue-taking overload in one go.

Source files¶

CMakeLists.txt
app.cpp
v1.cpp
v1.h
v2.cpp
v2.h