{"record":{"id":"b62607204e9cc1f8","repo":"go-delve/delve","slug":"could-not-load-swiss-map-group-v","errorCode":null,"errorMessage":"could not load swiss map group: %v","messagePattern":"could not load swiss map group: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"pkg/proc/mapiter.go","lineNumber":661,"sourceCode":"\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() {\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","sourceCodeStart":643,"sourceCodeEnd":679,"githubUrl":"https://github.com/go-delve/delve/blob/a23773e6c31361e43246bc43a424ee009679b174/pkg/proc/mapiter.go#L643-L679","documentation":"Set on a map Variable by loadCurrentGroup when sliceAccess on the groups array at it.groupIdx fails. Delve previously rewrote the groups pointer into a fake *[N]group array type; indexing it requires reading the group pointer at that array slot from target memory. Failure typically means the address is out of bounds of readable memory or the fake array index is invalid. Delve throws it because the group at the current index cannot be loaded.","triggerScenarios":"Iterating a swiss map when the group pointer for groupIdx cannot be read: groups pointer corrupted, groupIdx exceeding the real allocation, or unreadable heap memory (detached/exited process, bad core dump).","commonSituations":"Inspecting a map whose memory was freed or reallocated (reading stale variables after program resumed); corrupt core dump; Delve miscalculating group count due to layout mismatch causing out-of-range reads.","solutions":["Re-evaluate the map variable at a fresh breakpoint instead of using a stale copy captured before the map mutated","Upgrade Delve to match the Go runtime layout so group counts are computed correctly","Verify the process/core dump memory is fully available (full-heap core dump)","Reduce map inspection to len() and targeted key lookups if iteration keeps failing"],"exampleFix":null,"handlingStrategy":"type-guard","validationCode":"if v.Unreadable != nil { return } // group memory unreadable; re-evaluate at a stable stop point","typeGuard":"func usable(v *proc.Variable) bool { return v != nil && v.Unreadable == nil && v.Addr != 0 }","tryCatchPattern":"if v.Unreadable != nil { return nil, fmt.Errorf(\"map iteration stopped early: %w\", v.Unreadable) }","preventionTips":["Inspect maps only while the process is stopped at a breakpoint","Use full-heap core dumps for post-mortem analysis","Re-evaluate variables instead of reusing pointers captured before resuming","Keep Delve updated so computed group counts match the runtime layout"],"tags":["go","debugger","memory","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"}