{"record":{"id":"5deed04ef67da19a","repo":"go-delve/delve","slug":"could-not-load-swiss-table-group-lengthmask-v","errorCode":null,"errorMessage":"could not load swiss table group lengthMask: %v","messagePattern":"could not load swiss table group lengthMask: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"pkg/proc/mapiter.go","lineNumber":640,"sourceCode":"\tgroups, err2 := tab.toField(it.tableFieldGroups)\n\tif err2 != nil {\n\t\tit.v.Unreadable = fmt.Errorf(\"could not load swiss table groups field: %v\", err2)\n\t\treturn\n\t}\n\tr.groups, err2 = groups.toField(it.groupsFieldData)\n\tif err2 != nil {\n\t\tit.v.Unreadable = fmt.Errorf(\"could not load swiss table groups data: %v\", err2)\n\t\treturn\n\t}\n\n\tfield, err2 = groups.toField(it.groupsFieldLengthMask)\n\tif err2 != nil {\n\t\tit.v.Unreadable = fmt.Errorf(\"could not load swiss table groups lengthMask field: %v\", err2)\n\t\treturn\n\t}\n\tgroupsLengthMask, err := field.asUint()\n\tif err != nil {\n\t\tit.v.Unreadable = fmt.Errorf(\"could not load swiss table group lengthMask: %v\", err)\n\t\treturn\n\t}\n\n\t// convert the type of groups from *group to *[len]group so that it's easier to use\n\tr.groups.DwarfType = pointerTo(fakeArrayType(groupsLengthMask+1, it.groupType), it.v.bi.Arch)\n\tr.groups.RealType = r.groups.DwarfType\n\tr.groups = r.groups.maybeDereference()\n\n\tif r.groups.Addr == 0 {\n\t\tit.v.Unreadable = errSwissTableNilGroups\n\t\treturn\n\t}\n\n\tit.tab = r\n}\n\n// loadCurrentGroup loads the group at index it.groupIdx of it.tab into it.group\nfunc (it *mapIteratorSwiss) loadCurrentGroup() {","sourceCodeStart":622,"sourceCodeEnd":658,"githubUrl":"https://github.com/go-delve/delve/blob/a23773e6c31361e43246bc43a424ee009679b174/pkg/proc/mapiter.go#L622-L658","documentation":"Set on a map Variable when the lengthMask field was found but field.asUint() failed to convert it to an unsigned integer. Delve expects lengthMask to be a plain unsigned integer type; any other DWARF type (or an unreadable value) makes the group-count computation impossible. Delve throws it because it must build a fake *[N]group type to walk the groups array.","triggerScenarios":"Iterating a swiss map where loadCurrentTable resolved lengthMask but its DWARF type is not a uint kind (e.g. changed type in a new Go runtime, or bitfield/typedef mismatch).","commonSituations":"Newer/older Go toolchain with altered internal/runtime/maps types; type info corrupted by aggressive DWARF compression or post-link tools; Delve version lagging behind the Go release used to build the binary.","solutions":["Update Delve to the version matching your Go toolchain","Rebuild the binary with a supported Go release and default debug flags","Check for post-processing of the binary (strip, objcopy) that damages DWARF and remove it","Use program-side logging to inspect the map instead"],"exampleFix":"// before: stripped binary\nstrip app && dlv exec app\n// after: keep symbols\ndlv exec app","handlingStrategy":"type-guard","validationCode":"if v.Unreadable != nil { return } // do not attempt to enumerate children of an unreadable map","typeGuard":"func safeChildren(v *proc.Variable) ([]*proc.Variable, bool) { if v == nil || v.Unreadable != nil { return nil, false }; return v.Children, true }","tryCatchPattern":"if err := v.Unreadable; err != nil { log.Debug(err); return nil, err }","preventionTips":["Avoid post-link binary processing (strip, objcopy, obfuscators) on debug targets","Upgrade Delve after every Go toolchain upgrade","Confirm struct DWARF completeness with readelf --debug-dump=info","Always check Unreadable before reading Variable fields like Children or Value"],"tags":["go","debugger","dwarf","swiss-map"],"backgroundTag":"swiss-map-layout-mismatch","analyzedSha":"a23773e6c31361e43246bc43a424ee009679b174","analyzedAt":"2026-08-31T15:12:45.221Z","schemaVersion":2},"datasetVersion":"2026-08-31T19:17:28.585Z"}