Type Alias warningSAXFunc 

pub type warningSAXFunc = unsafe extern "C" fn(ctx: *mut c_void, msg: *const c_char);

Callback for warnings (printf-style, variadic at C call site).

UPSTREAM-PARITY

The ... is implicit in C; Rust type cannot express variadic extern “C” on stable. The function pointer ABI is identical — C callers pass variadic arguments and the callee uses va_list internally.