{"record":{"id":"168f9654406d1876","repo":"go-delve/delve","slug":"could-not-load-swiss-table-index-v","errorCode":null,"errorMessage":"could not load swiss table index: %v","messagePattern":"could not load swiss table index: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"pkg/proc/mapiter.go","lineNumber":618,"sourceCode":"func (it *mapIteratorSwiss) loadCurrentTable() {\n\ttab, err := it.dirPtr.sliceAccess(int(it.dirIdx))\n\tif err != nil || tab == nil || tab.Unreadable != nil {\n\t\tit.v.Unreadable = errSwissTableCouldNotLoad\n\t\treturn\n\t}\n\n\ttab = tab.maybeDereference()\n\n\tr := &swissTable{}\n\n\tfield, err2 := tab.toField(it.tableFieldIndex)\n\tif err2 != nil {\n\t\tit.v.Unreadable = fmt.Errorf(\"could not load swiss table index field: %v\", err2)\n\t\treturn\n\t}\n\tr.index, err = field.asInt()\n\tif err != nil {\n\t\tit.v.Unreadable = fmt.Errorf(\"could not load swiss table index: %v\", err)\n\t\treturn\n\t}\n\n\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","sourceCodeStart":600,"sourceCodeEnd":636,"githubUrl":"https://github.com/go-delve/delve/blob/a23773e6c31361e43246bc43a424ee009679b174/pkg/proc/mapiter.go#L600-L636","documentation":"This error is set on a map Variable's Unreadable field while Delve walks a Go swiss map (Go 1.24+ map implementation). During loadCurrentTable, Delve reads the 'index' field of the table struct from debugged-process memory; after extracting the field it calls asInt(), which fails if the field's DWARF type is not a plain signed integer. Delve throws this because it cannot interpret the table index without a well-typed integer, usually meaning the debug info does not match the running Go runtime's maps.Table layout.","triggerScenarios":"Iterating a map (e.g. printing it in the CLI, evaluating it via RPC, expanding it in an IDE) where loadCurrentTable successfully found a field named 'index' on the table struct, but field.asInt() returned an error (unexpected DWARF type, bitfield, or unreadable value).","commonSituations":"Debugging a binary built with a Go version whose internal/runtime/maps.Table struct differs from what Delve's swiss-map support expects; stripped or partially optimized debug info; attaching to a binary produced by a toolchain newer than the Delve version.","solutions":["Upgrade Delve to the latest version so its swiss map layout matches your Go toolchain","Rebuild the target binary with the same Go version Delve supports and without -ldflags=-w -s so DWARF info is complete","Verify 'go version' of the binary (go version <binary>) matches a Delve-supported release","If the map still fails, use alternatives: add temporary logging in the program or print len(map) and inspect via other means"],"exampleFix":"// before: built with unsupported Go version\ngo build -gcflags=\"-N -l\" -o app .\n// after: use a toolchain matching Delve's supported swiss map layout\ngo1.24.x build -gcflags=\"-N -l\" -o app .","handlingStrategy":"type-guard","validationCode":"// client side (Delve API consumer)\nif v := mapVar; v != nil && v.Unreadable != nil {\n    // do not use v.Value; surface v.Unreadable to the user\n}","typeGuard":"func readable(v *proc.Variable) bool { return v != nil && v.Unreadable == nil }","tryCatchPattern":"// Delve sets Unreadable instead of panicking; always check it after map evaluation\nif err := v.Unreadable; err != nil { return fmt.Errorf(\"map unreadable: %w\", err) }","preventionTips":["Keep Delve version in lockstep with the Go toolchain building the debugged binary","Always build debug targets with full DWARF (avoid -w -s)","Run 'go version <binary>' before debugging to confirm toolchain support","Check v.Unreadable after every variable evaluation instead of assuming Value is valid"],"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"}