llvm-project

d1e84bb9 - Thread Safety Analysis: Support attributes on function pointers (#191187)

Thread Safety Analysis: Support attributes on function pointers (#191187) Allow acquire_capability, release_capability, requires_capability, try_acquire_capability, assert_capability, and locks_excluded attributes (incl. their shared variants) on function pointer variables and struct fields. Calls through annotated function pointers are checked the same way as direct function calls. The attributes are placed on variable/field declarations, not on the function pointer type itself. This is a deliberate trade-off: making these "attributes" part of the type system would require diagnosing mismatched assignments, which would be a significant type-system extension with limited practical benefit, which would likely require promoting the TSA vocabulary to full type-qualifiers. Instead, the analysis trusts the annotations on the variable at the call site, and sticks with the attribute-based semantics. This matches the existing philosophy where the analysis tries to avoid false positives where possible and attribute mismatches on direct functions are likewise not hard errors or warnings (yet). The primary motivation is to avoid false positives in large C codebases, such as the Linux kernel [1], which tend to use structs containing function pointers to emulate subtype polymorphism and dynamic dispatch. [1] https://lore.kernel.org/all/20260409064221.GA8378@lst.de/