{"record":{"id":"a586d217b4e9e78b","repo":"golang/go","slug":"no-room-to-add-dwarf-info-need-at-least-d-paddin","errorCode":null,"errorMessage":"no room to add dwarf info. Need at least %d padding bytes, found %d","messagePattern":"no room to add dwarf info\\. Need at least (.+?) padding bytes, found (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"src/cmd/link/internal/ld/macho_combine_dwarf.go","lineNumber":152,"sourceCode":"\tlinkstart := Rnd(dwarfstart+int64(dwarfsize), *FlagRound)\n\tif _, err := outf.Seek(linkstart, 0); err != nil {\n\t\treturn err\n\t}\n\tif _, err := io.Copy(outf, exef); err != nil {\n\t\treturn err\n\t}\n\n\t// Now we need to update the headers.\n\ttextsect := exem.Section(\"__text\")\n\tif textsect == nil {\n\t\treturn fmt.Errorf(\"missing __text section\")\n\t}\n\n\tcmdOffset := imacho.FileHeaderSize(exem)\n\tdwarfCmdOffset := uint32(cmdOffset) + exem.FileHeader.Cmdsz\n\tavailablePadding := textsect.Offset - dwarfCmdOffset\n\tif availablePadding < realdwarf.Len {\n\t\treturn fmt.Errorf(\"no room to add dwarf info. Need at least %d padding bytes, found %d\", realdwarf.Len, availablePadding)\n\t}\n\t// First, copy the dwarf load command into the header. It will be\n\t// updated later with new offsets and lengths as necessary.\n\tif _, err := outf.Seek(int64(dwarfCmdOffset), 0); err != nil {\n\t\treturn err\n\t}\n\tif _, err := io.CopyN(outf, bytes.NewReader(realdwarf.Raw()), int64(realdwarf.Len)); err != nil {\n\t\treturn err\n\t}\n\tif _, err := outf.Seek(int64(unsafe.Offsetof(exem.FileHeader.Ncmd)), 0); err != nil {\n\t\treturn err\n\t}\n\tif err := binary.Write(outf, exem.ByteOrder, exem.Ncmd+1); err != nil {\n\t\treturn err\n\t}\n\tif err := binary.Write(outf, exem.ByteOrder, exem.Cmdsz+realdwarf.Len); err != nil {\n\t\treturn err\n\t}","sourceCodeStart":134,"sourceCodeEnd":170,"githubUrl":"https://github.com/golang/go/blob/b6b368adc57c96c3151d224d172029f233ead2c3/src/cmd/link/internal/ld/macho_combine_dwarf.go#L134-L170","documentation":"The DWARF load command must be inserted into the header padding between the end of existing load commands (`dwarfCmdOffset`) and the start of `__text`. If the available padding (`textsect.Offset - dwarfCmdOffset`) is smaller than the DWARF segment's load-command size (`realdwarf.Len`), there is no room and the link aborts rather than overwrite executable code.","triggerScenarios":"An executable with many load commands (large entitlements, many rpaths, many dylibs) consuming most header padding; a very large DWARF segment load command; an older SDK that left less default padding; binaries built with unusual `-pagezero_size` or segment-alignment flags that shrink the header gap.","commonSituations":"macOS apps with extensive entitlements/embedded dylibs; CI that injects many `-rpath` flags; large Go programs whose DWARF load command exceeds the default ~4KB header pad.","solutions":["Reduce the number of load commands (fewer rpaths, fewer embedded dylibs) to free header padding.","Increase the header padding via the external linker: `-extldflags='-headerpad 0x1000'` (or larger).","Strip DWARF instead of combining it (`-ldflags='-s -w'`) if you only need a shippable binary.","Split the program so the DWARF segment load command is smaller."],"exampleFix":"# before: DWARF load command too large for default header pad\ngo build -o bin/app ./...\n\n# after: request more header padding from the external linker\ngo build -ldflags='-extldflags=-headerpad_max_install_names -linkmode=external' -o bin/app ./...","handlingStrategy":"fallback","validationCode":"# Estimate header padding vs load-command count\nLCOUNT=$(otool -l bin/app 2>/dev/null | grep -c 'LC_')\necho \"load commands: $LCOUNT (more = less room for DWARF cmd)\"\n# If close to the limit, plan to strip DWARF or grow headerpad","typeGuard":null,"tryCatchPattern":"# Fall back to a stripped build if there is no header room for DWARF\nset +e\ngo build -o bin/app ./...\nrc=$?\nset -e\nif [ $rc -ne 0 ]; then\n  echo 'no room for DWARF; building stripped' >&2\n  go build -ldflags='-s -w' -o bin/app ./...\nfi","preventionTips":["Minimize rpaths and embedded dylibs to free header padding.","Request extra header padding via `-extldflags='-headerpad ...'`.","Strip DWARF (`-s -w`) for release builds that do not need it.","Avoid injecting many load commands via post-processing."],"tags":["linker","go-toolchain","macos","dwarf","mach-o","header-padding"],"backgroundTag":null,"analyzedSha":"b6b368adc57c96c3151d224d172029f233ead2c3","analyzedAt":"2026-08-12T00:22:02.250Z","schemaVersion":2},"datasetVersion":"2026-08-12T13:17:24.610Z"}