{"record":{"id":"eaed273526e836c2","repo":"go-delve/delve","slug":"could-not-load-swiss-map-group-ctrl-v","errorCode":null,"errorMessage":"could not load swiss map group ctrl: %v","messagePattern":"could not load swiss map group ctrl: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"pkg/proc/mapiter.go","lineNumber":670,"sourceCode":"\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() {\n\tgroup, err := it.tab.groups.sliceAccess(int(it.groupIdx))\n\tif err != nil {\n\t\tit.v.Unreadable = fmt.Errorf(\"could not load swiss map group: %v\", err)\n\t\treturn\n\t}\n\n\tg := &swissGroup{}\n\n\tvar err2 error\n\tctrl, err2 := group.toField(it.groupFieldCtrl)\n\tif err2 != nil {\n\t\tit.v.Unreadable = fmt.Errorf(\"could not load swiss map group ctrl: %v\", err2)\n\t\treturn\n\t}\n\tg.ctrls = make([]byte, ctrl.DwarfType.Size())\n\t_, err = ctrl.mem.ReadMemory(g.ctrls, ctrl.Addr)\n\tif err != nil {\n\t\tit.v.Unreadable = err\n\t\treturn\n\t}\n\n\tif it.mapsplitgroup {\n\t\tg.keys, err2 = group.toField(it.groupFieldKeys)\n\t\tif err2 != nil {\n\t\t\tit.v.Unreadable = fmt.Errorf(\"could not load swiss map group keys: %v\", err2)\n\t\t\treturn\n\t\t}\n\t\tg.elems, err2 = group.toField(it.groupFieldElems)\n\t\tif err2 != nil {\n\t\t\tit.v.Unreadable = fmt.Errorf(\"could not load swiss map group elems: %v\", err2)","sourceCodeStart":652,"sourceCodeEnd":688,"githubUrl":"https://github.com/go-delve/delve/blob/a23773e6c31361e43246bc43a424ee009679b174/pkg/proc/mapiter.go#L652-L688","documentation":"Set on a map Variable by loadCurrentGroup when the 'ctrl' (control bytes) field of a swiss group cannot be resolved from DWARF. Delve needs the control bytes to skip empty/deleted slots via slotIsEmptyOrDeleted. Failure means the group struct type lacks a readable 'ctrl' field per the debug info. Delve throws it because iteration cannot classify slots without the control word.","triggerScenarios":"Iterating a swiss map when group.toField(it.groupFieldCtrl) fails: the group type in DWARF has no 'ctrl' field, or its type differs from what the Delve version expects (e.g. ctrl vs ctrl element type changes across Go versions).","commonSituations":"Go runtime internals changed (groupSlider/group layout refactors); binary built with a Go release newer than the Delve version; partially optimized builds omitting struct field info.","solutions":["Upgrade Delve to a release supporting your Go version's group layout","Rebuild the target with a supported Go toolchain and complete DWARF","Check 'go version <binary>' and consult Delve release notes for supported Go versions","As a workaround, copy map data into a slice/struct the debugger reads reliably before inspecting"],"exampleFix":null,"handlingStrategy":"type-guard","validationCode":"if v.Unreadable != nil { return v.Unreadable } // group ctrl field missing in DWARF","typeGuard":"func iterableView(v *proc.Variable) bool { return v != nil && v.Unreadable == nil }","tryCatchPattern":"if v.Unreadable != nil { showRawPointerView(v); return } // degrade gracefully","preventionTips":["Match Delve release to the target's Go version (check release notes)","Build with -gcflags=\"-N -l\" for debug sessions","Smoke-test swiss map inspection after Go upgrades","Check Unreadable before consuming iteration results in client code"],"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"}