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case218 — a GLOBAL export loss stays BREAKING under a binding: weak rule

Field Value
Verdict 🔴 BREAKING
Category Breaking
Classification Rule
Platforms Linux
Flags ABI break
Detected ChangeKinds func_removed_elf_only
Source files catalog/cases/case218_export_loss_strong_binding_stays_breaking/
Rule family export-loss-strong-binding-stays-breaking
Subject ELF export and linker metadata

Verdict and consumer impact

This is the sibling of case217_export_loss_weak_binding_demoted. It uses the same policy.yaml and the same three WEAK losses, and NEW also drops ns::strong_fn, a GLOBAL export declared in the public header. A consumer that calls strong_fn fails to link or bind against NEW, so this is a real break.

The binding: weak rule matches only WEAK findings. The strong_fn finding carries symbol_binding: "global", so the rule does not match it and the run stays BREAKING, exit code 4. The WEAK losses are still demoted to a risk; the verdict is set by the strong removal alone.

Old/new diff

v1 (OLD) v2 (NEW)
hdr_inline() called from Pub::g(), emitted WEAK not emitted (as in case217)
weak_undeclared() __attribute__((weak)), not in any header not defined
detail::P<float> ctor instantiated by Pub::q() not instantiated
strong_fn() GLOBAL, declared and defined declared in v2.h, not defined

abicheck command

abicheck dump libv1.so -H v1.h -o v1.json
abicheck dump libv2.so -H v2.h -o v2.json
rm libv1.so
abicheck compare v1.json v2.json --policy policy.yaml

Expected abicheck finding

  • Verdict: BREAKING, exit code 4.
  • The WEAK findings (func_visibility_changed on hdr_inline, func_removed_elf_only on weak_undeclared and the P<float> constructor) carry symbol_binding: "weak" and are reclassified to risk.
  • func_visibility_changed on strong_fn carries symbol_binding: "global" and is not reclassified, so it keeps the run at BREAKING.

Minimum evidence

min_evidence: L2 (public headers), as in case217.

Why abicheck catches it

Same mechanism as case217: the ELF .dynsym gives each finding its old-side binding, and the binding: selector compares that value (policy/selectors.py). Because the selector compares the value, a GLOBAL finding is never matched by a rule written for WEAK ones.

Source files

  • policy.yaml
  • v1.cpp
  • v1.h
  • v2.cpp
  • v2.h

See also: Compatibility Catalog · All BREAKING cases · Category: Breaking · Rule: Strong export loss stays breaking under a binding rule · Subject: ELF export and linker metadata.