Fix decode error for dictionary-encoded structs#354
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tigrannajaryan merged 1 commit intomainfrom Feb 15, 2026
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The problem occurs when decoding dictionary-encoded structs and the refNum is 0, which corresponds to nil struct. Nil is not allowed for structs unless they are optional. Decoding error is found by FuzzSampleReader and corresponding seeds are included in this PR.
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Pull request overview
Fixes a decode failure when dictionary-encoded struct references use refNum == 0 (nil) in contexts where nil structs are invalid, and adds fuzz-regression seeds capturing the issue.
Changes:
- Add explicit nil checks after decoding dict-encoded struct pointers (reject nil for non-optional/invalid cases).
- Add a generic
pkg.ErrDecodeErrorsentinel used for “invalid decode state” returns. - Refactor many generated decoders to use inline
if err := ...; err != nilstyle and adjust oneof decoders to surface buffer errors immediately after reading the variant type.
Reviewed changes
Copilot reviewed 51 out of 51 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
| stefc/templates/go/struct.go.tmpl | Add nil rejection for non-optional dict-encoded pointer fields after decode; simplify error handling. |
| stefc/templates/go/oneof.go.tmpl | Check buffer error after reading oneof type; reject nil for dict-encoded pointer variants; return nil when no further buffer interaction is needed. |
| stefc/templates/go/array.go.tmpl | Reject nil elements for dict-encoded struct arrays; simplify error handling in loops. |
| go/pkg/errors.go | Introduce ErrDecodeError decode-error sentinel. |
| go/otel/otelstef/uint64array.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/summaryvalue.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/spanstatus.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/spans.go | Inline decode error handling; reject nil for non-optional dict-decoded struct pointers. |
| go/otel/otelstef/span.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/scope.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/resource.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/quantilevaluearray.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/quantilevalue.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/pointvalue.go | Oneof: check buffer error after reading type; return nil at end. |
| go/otel/otelstef/point.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/metrics.go | Inline decode error handling; reject nil for non-optional dict-decoded struct pointers. |
| go/otel/otelstef/metric.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/linkarray.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/link.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/histogramvalue.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/float64array.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/exphistogramvalue.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/exphistogrambuckets.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/exemplarvalue.go | Oneof: check buffer error after reading type; return nil at end. |
| go/otel/otelstef/exemplararray.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/exemplar.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/eventarray.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/event.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/envelope.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/anyvaluearray.go | Inline decode error handling style cleanup. |
| go/otel/otelstef/anyvalue.go | Oneof: check buffer error after reading type; return nil at end. |
| examples/profile/internal/profile/testdata/fuzz/FuzzSampleReader/d369e9adf349dff1 | Add fuzz seed reproducing the decode issue. |
| examples/profile/internal/profile/testdata/fuzz/FuzzSampleReader/814b20d96326fa74 | Add fuzz seed reproducing the decode issue. |
| examples/profile/internal/profile/stringarray.go | Inline decode error handling style cleanup. |
| examples/profile/internal/profile/samplevaluetype.go | Inline decode error handling style cleanup. |
| examples/profile/internal/profile/samplevaluearray.go | Inline decode error handling style cleanup. |
| examples/profile/internal/profile/samplevalue.go | Inline decode error handling; reject nil for non-optional dict-decoded struct pointers. |
| examples/profile/internal/profile/sample.go | Inline decode error handling style cleanup. |
| examples/profile/internal/profile/profilemetadata.go | Inline decode error handling; reject nil for non-optional dict-decoded struct pointers. |
| examples/profile/internal/profile/numvalue.go | Inline decode error handling style cleanup. |
| examples/profile/internal/profile/mapping.go | Inline decode error handling style cleanup. |
| examples/profile/internal/profile/locationarray.go | Reject nil elements for dict-encoded struct arrays; inline decode error handling. |
| examples/profile/internal/profile/location.go | Inline decode error handling; reject nil for non-optional dict-decoded struct pointers. |
| examples/profile/internal/profile/linearray.go | Inline decode error handling style cleanup. |
| examples/profile/internal/profile/line.go | Inline decode error handling; reject nil for non-optional dict-decoded struct pointers. |
| examples/profile/internal/profile/labelvalue.go | Oneof: check buffer error after reading type; return nil at end. |
| examples/profile/internal/profile/function.go | Inline decode error handling style cleanup. |
| examples/jsonl/internal/jsonstef/record.go | Inline decode error handling style cleanup. |
| examples/jsonl/internal/jsonstef/jsonvaluearray.go | Inline decode error handling style cleanup. |
| examples/jsonl/internal/jsonstef/jsonvalue.go | Oneof: check buffer error after reading type; return nil at end. |
| examples/ints/internal/ints/record.go | Inline decode error handling style cleanup. |
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Merging this one to continue fuzzing. |
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The problem occurs when decoding dictionary-encoded structs and the refNum is 0, which corresponds to nil struct. Nil is not allowed for structs unless they are optional.
Decoding error is found by FuzzSampleReader and corresponding seeds are included in this PR.