{"record":{"id":"e6535fc3d5f2ea7a","repo":"ClementTsang/bottom","slug":"failed-to-get-process-for-pid-pid","errorCode":null,"errorMessage":"failed to get process for pid {pid}","messagePattern":"failed to get process for pid (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"src/collection/processes/macos/sysctl_bindings.rs","lineNumber":283,"sourceCode":"pub(crate) fn kinfo_process(pid: Pid) -> Result<kinfo_proc> {\n    let mut name: [i32; 4] = [CTL_KERN, KERN_PROC, KERN_PROC_PID, pid];\n    let mut size = mem::size_of::<kinfo_proc>();\n    let mut info = mem::MaybeUninit::<kinfo_proc>::uninit();\n\n    // SAFETY: libc binding, we assume all arguments are valid.\n    let result = unsafe {\n        libc::sysctl(\n            name.as_mut_ptr(),\n            4,\n            info.as_mut_ptr() as *mut libc::c_void,\n            &mut size,\n            std::ptr::null_mut(),\n            0,\n        )\n    };\n\n    if result < 0 {\n        bail!(\"failed to get process for pid {pid}\");\n    }\n\n    // sysctl succeeds but size is zero, happens when process has gone away\n    if size == 0 {\n        bail!(\"failed to get process for pid {pid}\");\n    }\n\n    // SAFETY: info is initialized if result succeeded and returned a\n    // non-negative result. If sysctl failed, it returns -1 with errno set.\n    //\n    // Source: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/sysctl.3.html\n    unsafe { Ok(info.assume_init()) }\n}\n\n#[cfg(test)]\nmod test {\n    use std::mem;\n","sourceCodeStart":265,"sourceCodeEnd":301,"githubUrl":"https://github.com/ClementTsang/bottom/blob/b77d3175028849824e987c35177e8f61450d72e7/src/collection/processes/macos/sysctl_bindings.rs#L265-L301","documentation":"kinfo_process calls libc::sysctl with CTL_KERN/KERN_PROC/KERN_PROC_PID to fetch the kinfo_proc for a PID, and bails when sysctl returns < 0 (errno set). This means the kernel could not return process information for the requested PID. The library uses this as the signal that the process record is unobtainable on macOS.","triggerScenarios":"sysctl(KERN_PROC_PID, pid) returns -1 — the PID does not exist (ESRCH), the caller lacks permission for that process (EPERM, e.g. other users' processes under SIP), or an invalid pid value was passed.","commonSituations":"Race between listing PIDs via KERN_PROC_ALL and fetching details — the process exited in between; querying PID 0 or kernel-owned PIDs; sandboxed builds where sysctl process introspection is restricted.","solutions":["Treat it as a benign race: skip the PID and continue with the rest of the process list","Re-check the process exists (e.g. via kill(pid, 0)) before fetching kinfo_proc","Check errno via std::io::Error::last_os_error() to distinguish ESRCH (gone) from EPERM (permissions)","If EPERM is persistent, run with fewer restrictions or accept partial process data"],"exampleFix":"// before\nif result < 0 {\n    bail!(\"failed to get process for pid {pid}\");\n}\n// after\nif result < 0 {\n    let e = io::Error::last_os_error();\n    if e.kind() == io::ErrorKind::NotFound || e.raw_os_error() == Some(libc::ESRCH) {\n        return Err(ProcessGone(pid).into()); // skip gracefully\n    }\n    bail!(\"failed to get process for pid {pid}: {e}\");\n}","handlingStrategy":"try-catch","validationCode":"// check the process is alive before fetching kinfo_proc\nfn pid_alive(pid: i32) -> bool {\n    unsafe { libc::kill(pid, 0) == 0 }\n}","typeGuard":null,"tryCatchPattern":"match kinfo_process(pid) {\n    Ok(info) => Some(info),\n    Err(e) if e.to_string().contains(\"failed to get process\") => None, // raced exit\n    Err(e) => return Err(e),\n}","preventionTips":["Treat per-PID sysctl failures as expected races, not fatal errors","Re-list PIDs from a fresh snapshot rather than caching them","Distinguish ESRCH from EPERM by inspecting errno for better skip/retry decisions"],"tags":["macos","sysctl","processes","libc"],"backgroundTag":"resource-not-found","analyzedSha":"b77d3175028849824e987c35177e8f61450d72e7","analyzedAt":"2026-09-07T14:53:21.246Z","contentChangedAt":"2026-09-07T14:53:21.246Z","schemaVersion":2},"datasetVersion":"2026-09-16T04:17:20.429Z"}