Skip memcpy when source vector is empty in MapBufferBuilder::build#57398
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Summary: `buckets_.data()` and `dynamicData_.data()` return `nullptr` when the vector is empty, and glibc marks `memcpy`'s src argument as `nonnull`. Passing `nullptr` is UB even with a size of 0, which trips UBSan halt-on-error on any MapBuffer that has no buckets (`EMPTY()`) or no dynamic-data entries (scalar-only maps). Guard both memcpys with an empty check. Changelog: [General][Fixed] - Avoid `memcpy(_, nullptr, 0)` UB in `MapBufferBuilder::build` for empty / scalar-only MapBuffers Reviewed By: cortinico Differential Revision: D110316404
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…eact#57398) Summary: `buckets_.data()` and `dynamicData_.data()` return `nullptr` when the vector is empty, and glibc marks `memcpy`'s src argument as `nonnull`. Passing `nullptr` is UB even with a size of 0, which trips UBSan halt-on-error on any MapBuffer that has no buckets (`EMPTY()`) or no dynamic-data entries (scalar-only maps). Guard both memcpys with an empty check. Changelog: [General][Fixed] - Avoid `memcpy(_, nullptr, 0)` UB in `MapBufferBuilder::build` for empty / scalar-only MapBuffers Reviewed By: cortinico Differential Revision: D110316404
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Summary:
buckets_.data()anddynamicData_.data()returnnullptrwhen the vector is empty, and glibc marksmemcpy's src argument asnonnull. Passingnullptris UB even with a size of 0, which trips UBSan halt-on-error on any MapBuffer that has no buckets (EMPTY()) or no dynamic-data entries (scalar-only maps). Guard both memcpys with an empty check.Changelog:
[General][Fixed] - Avoid
memcpy(_, nullptr, 0)UB inMapBufferBuilder::buildfor empty / scalar-only MapBuffersReviewed By: cortinico
Differential Revision: D110316404