{"record":{"id":"a6828eb761b01e18","repo":"go-delve/delve","slug":"bad-swiss-map-groups-pointer-is-nil","errorCode":null,"errorMessage":"bad swiss map, groups pointer is nil","messagePattern":"bad swiss map, groups pointer is nil","errorType":"error_code","errorClass":"errSwissTableNilGroups","httpStatus":null,"severity":"error","filePath":"pkg/proc/mapiter.go","lineNumber":385,"sourceCode":"\tgroups *Variable\n}\n\ntype swissGroup struct {\n\tctrls []byte\n\n\t// GOEXPERIMENT=nomapsplitgroup\n\tslots *Variable\n\n\t// GOEXPERIMENT=mapsplitgroup\n\tkeys, elems *Variable\n}\n\nvar (\n\terrSwissTableCouldNotLoad  = errors.New(\"could not load one of the tables\")\n\terrSwissMapBadType         = errors.New(\"swiss table type does not have some required fields\")\n\terrSwissMapBadTableField   = errors.New(\"swiss table bad table field\")\n\terrSwissMapBadGroupTypeErr = errors.New(\"bad swiss map type, group type lacks some required fields\")\n\terrSwissTableNilGroups     = errors.New(\"bad swiss map, groups pointer is nil\")\n)\n\n// loadTypes determines the correct type for it.dirPtr:  the linker records\n// this type as **table but in reality it is either *[dirLen]*table for\n// large maps or *group for small maps, when it.dirLen == 0.\nfunc (it *mapIteratorSwiss) loadTypes() {\n\ttableptrptrtyp, ok := it.dirPtr.DwarfType.(*godwarf.PtrType)\n\tif !ok {\n\t\tit.v.Unreadable = errSwissMapBadTableField\n\t\treturn\n\t}\n\ttableptrtyp, ok := tableptrptrtyp.Type.(*godwarf.PtrType)\n\tif !ok {\n\t\tit.v.Unreadable = errSwissMapBadTableField\n\t\treturn\n\t}\n\tit.tableType, ok = tableptrtyp.Type.(*godwarf.StructType)\n\tif !ok {","sourceCodeStart":367,"sourceCodeEnd":403,"githubUrl":"https://github.com/go-delve/delve/blob/a23773e6c31361e43246bc43a424ee009679b174/pkg/proc/mapiter.go#L367-L403","documentation":"loadCurrentTable checks the map's groups pointer before iterating. errSwissTableNilGroups is returned when the groups pointer of a swiss map is nil (or could not be read as non-nil), so there are no groups to iterate.","triggerScenarios":"Iterating a swiss map whose table's groups pointer reads as nil in target memory during loadCurrentTable — e.g. the map structure in memory is zeroed, the pointer read failed, or the loaded map variable is stale.","commonSituations":"Inspecting a map that was not initialized as expected (zero-valued struct embedding a map); reading a map from a stale or mismatched core dump; races where the map is being modified concurrently in the target.","solutions":["Confirm the map variable is the live, initialized one (print its address and header fields)","Re-read the variable after the process has run (an in-progress map assignment can transiently expose nil groups)","If debugging a core dump, verify it was captured from the same binary and is not truncated"],"exampleFix":null,"handlingStrategy":"retry","validationCode":"// Check the map is initialized and live before iterating:\n//   print &m   // non-nil address\n//   print m    // a count > 0 or nil indicates init state","typeGuard":null,"tryCatchPattern":"val, err := printMap(m)\nif err != nil && strings.Contains(err.Error(), \"groups pointer is nil\") {\n    contAndWait()           // let any in-progress map assignment finish\n    val, err = printMap(m)\n}","preventionTips":["Halt the target at stable points (not mid-map-construction)","Match core dumps to the exact binary build","Ensure the map variable is initialized before inspecting"],"tags":["go","maps","swiss-table","memory"],"backgroundTag":"swiss-map-iteration-failure","analyzedSha":"a23773e6c31361e43246bc43a424ee009679b174","analyzedAt":"2026-08-31T15:12:45.221Z","schemaVersion":2},"datasetVersion":"2026-08-31T19:17:28.585Z"}