{"record":{"id":"785445976e70f410","repo":"go-delve/delve","slug":"bad-swiss-map-type-group-type-lacks-some-required","errorCode":null,"errorMessage":"bad swiss map type, group type lacks some required fields","messagePattern":"bad swiss map type, group type lacks some required fields","errorType":"error_code","errorClass":"errSwissMapBadGroupTypeErr","httpStatus":null,"severity":"error","filePath":"pkg/proc/mapiter.go","lineNumber":384,"sourceCode":"\tindex  int64\n\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)","sourceCodeStart":366,"sourceCodeEnd":402,"githubUrl":"https://github.com/go-delve/delve/blob/a23773e6c31361e43246bc43a424ee009679b174/pkg/proc/mapiter.go#L366-L402","documentation":"The swiss map iterator needs the group struct to contain specific fields to read key/elem slots. errSwissMapBadGroupTypeErr is returned by loadTypes when the group type found in the target's DWARF lacks some required fields, so Delve cannot decode groups of the map.","triggerScenarios":"Evaluating a swiss map when the resolved group type (from the table's groups field or, for small maps, from dirPtr when dirLen==0) is missing required group fields during loadTypes.","commonSituations":"Go runtime releases that changed internal/runtime/maps.group layout while an older Delve is used; custom GOEXPERIMENT builds; binaries whose runtime type info was altered or partially stripped.","solutions":["Update Delve to the version matching the target binary's Go release","Rebuild the binary with a standard Go release and full debug symbols","Confirm no GOEXPERIMENT is active that changes map internals, or use a Delve build that supports it"],"exampleFix":null,"handlingStrategy":"validation","validationCode":"// Verify no layout-altering experiments and matching toolchain:\n//   $ go env GOEXPERIMENT   # should be empty for debug builds\n//   $ go version <binary> && dlv version","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Unset GOEXPERIMENT builds that change map internals when debugging","Upgrade Delve after every Go minor upgrade","Rebuild with full symbols; partial DWARF breaks group type discovery"],"tags":["go","maps","swiss-table","dwarf"],"backgroundTag":"swiss-map-iteration-failure","analyzedSha":"a23773e6c31361e43246bc43a424ee009679b174","analyzedAt":"2026-08-31T15:12:45.221Z","schemaVersion":2},"datasetVersion":"2026-08-31T19:17:28.585Z"}