Int64 attribute is converted to Int32

[sjdaines]

Describe the bug

A Julia Int64 (or Vector{Int64}) attribute is written to netcdf as Int32

(tested with NetCDF dataset attributes, not tried NetCDF variable attributes)

Edit: see comment below, looks like this is an intentional conversion to deal with a netcdf limitation?

To Reproduce

import NCDatasets
ds = NCDatasets.NCDataset("/tmp/test.nc","c")
v_i64 = 42
@assert typeof(v_i64) === Int64
ds.attrib["testInt64"] = 42
typeof(ds.attrib["testInt64"])

Int32

Expected behavior

Int64 attributes should remain as Int64

Environment

versioninfo()
Julia Version 1.10.3
Commit 0b4590a5507 (2024-04-30 10:59 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 12 × AMD Ryzen 5 7600 6-Core Processor
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, znver3)
Threads: 1 default, 0 interactive, 1 GC (on 12 virtual cores)
Environment:
  JULIA_EDITOR = code
  JULIA_NUM_THREADS = 

• NCDatasets version: v0.14.4
• Output of using Pkg; Pkg.status(mode=PKGMODE_MANIFEST)

julia> using Pkg; Pkg.status(mode=PKGMODE_MANIFEST)
Status `~/PALEO/PALEOdev.jl/PALEOexamples/Manifest.toml`
 [47edcb42] ADTypes v1.2.1
 [a4c015fc] ANSIColoredPrinters v0.0.1
 [1520ce14] AbstractTrees v0.4.5
 [7d9f7c33] Accessors v0.1.36
 [79e6a3ab] Adapt v4.0.4
 [ec485272] ArnoldiMethod v0.4.0
 [4fba245c] ArrayInterface v7.10.0
 [4c555306] ArrayLayouts v1.9.3
 [bf4720bc] AssetRegistry v0.1.0
 [13072b0f] AxisAlgorithms v1.1.0
 [6e4b80f9] BenchmarkTools v1.5.0
 [d1d4a3ce] BitFlags v0.1.8
 [62783981] BitTwiddlingConvenienceFunctions v0.1.5
 [ad839575] Blink v0.12.9
 [e1450e63] BufferedStreams v1.2.1
 [fa961155] CEnum v0.5.0
 [179af706] CFTime v0.1.3
 [2a0fbf3d] CPUSummary v0.2.5
 [336ed68f] CSV v0.10.14
 [d360d2e6] ChainRulesCore v1.23.0
 [fb6a15b2] CloseOpenIntervals v0.1.12
 [da1fd8a2] CodeTracking v1.3.5
 [944b1d66] CodecZlib v0.7.4
 [35d6a980] ColorSchemes v3.25.0
 [3da002f7] ColorTypes v0.11.5
 [c3611d14] ColorVectorSpace v0.10.0
 [5ae59095] Colors v0.12.11
 [1fbeeb36] CommonDataModel v0.3.6
 [38540f10] CommonSolve v0.2.4
 [bbf7d656] CommonSubexpressions v0.3.0
 [34da2185] Compat v4.15.0
 [a33af91c] CompositionsBase v0.1.2
 [2569d6c7] ConcreteStructs v0.2.3
 [f0e56b4a] ConcurrentUtilities v2.4.1
 [8f4d0f93] Conda v1.10.0
 [187b0558] ConstructionBase v1.5.5
 [d38c429a] Contour v0.6.3
 [adafc99b] CpuId v0.3.1
 [a8cc5b0e] Crayons v4.1.1
 [9a962f9c] DataAPI v1.16.0
 [a93c6f00] DataFrames v1.6.1
 [864edb3b] DataStructures v0.18.20
 [e2d170a0] DataValueInterfaces v1.0.0
 [8bb1440f] DelimitedFiles v1.9.1
 [2b5f629d] DiffEqBase v6.151.1
 [163ba53b] DiffResults v1.1.0
 [b552c78f] DiffRules v1.15.1
⌅ [3c3547ce] DiskArrays v0.3.23
 [b4f34e82] Distances v0.10.11
 [ffbed154] DocStringExtensions v0.9.3
 [e30172f5] Documenter v1.4.1
 [4e289a0a] EnumX v1.0.4
 [f151be2c] EnzymeCore v0.7.2
 [460bff9d] ExceptionUnwrapping v0.1.10
 [d4d017d3] ExponentialUtilities v1.26.1
 [e2ba6199] ExprTools v0.1.10
 [8f5d6c58] EzXML v1.2.0
 [c87230d0] FFMPEG v0.4.1
 [7034ab61] FastBroadcast v0.2.8
 [9aa1b823] FastClosures v0.3.2
 [29a986be] FastLapackInterface v2.0.3
 [5789e2e9] FileIO v1.16.3
 [48062228] FilePathsBase v0.9.21
 [1a297f60] FillArrays v1.11.0
 [6a86dc24] FiniteDiff v2.23.1
 [53c48c17] FixedPointNumbers v0.8.5
 [1fa38f19] Format v1.3.7
 [f6369f11] ForwardDiff v0.10.36
 [069b7b12] FunctionWrappers v1.1.3
 [77dc65aa] FunctionWrappersWrappers v0.1.3
 [de31a74c] FunctionalCollections v0.5.0
 [46192b85] GPUArraysCore v0.1.6
 [28b8d3ca] GR v0.73.5
 [c145ed77] GenericSchur v0.5.4
⌃ [d7ba0133] Git v1.3.0
 [86223c79] Graphs v1.11.0
 [42e2da0e] Grisu v1.0.2
 [f67ccb44] HDF5 v0.17.2
 [cd3eb016] HTTP v1.10.8
 [9fb69e20] Hiccup v0.2.2
 [3e5b6fbb] HostCPUFeatures v0.1.16
 [7073ff75] IJulia v1.24.2
 [b5f81e59] IOCapture v0.2.4
 [615f187c] IfElse v0.1.1
 [5903a43b] Infiltrator v1.8.2
 [d25df0c9] Inflate v0.1.4
 [842dd82b] InlineStrings v1.4.0
 [a98d9a8b] Interpolations v0.15.1
 [3587e190] InverseFunctions v0.1.14
 [41ab1584] InvertedIndices v1.3.0
 [92d709cd] IrrationalConstants v0.2.2
 [82899510] IteratorInterfaceExtensions v1.0.0
 [033835bb] JLD2 v0.4.48
 [1019f520] JLFzf v0.1.7
 [692b3bcd] JLLWrappers v1.5.0
 [97c1335a] JSExpr v0.5.4
 [682c06a0] JSON v0.21.4
 [aa1ae85d] JuliaInterpreter v0.9.31
 [ef3ab10e] KLU v0.6.0
 [ba0b0d4f] Krylov v0.9.6
 [8ac3fa9e] LRUCache v1.6.1
 [7f56f5a3] LSODA v0.7.5
 [b964fa9f] LaTeXStrings v1.3.1
 [23fbe1c1] Latexify v0.16.3
 [10f19ff3] LayoutPointers v0.1.15
 [0e77f7df] LazilyInitializedFields v1.2.2
 [50d2b5c4] Lazy v0.15.1
⌅ [5078a376] LazyArrays v1.10.0
 [d3d80556] LineSearches v7.2.0
 [7ed4a6bd] LinearSolve v2.30.0
 [2ab3a3ac] LogExpFunctions v0.3.27
 [e6f89c97] LoggingExtras v1.0.3
 [bdcacae8] LoopVectorization v0.12.170
 [6f1432cf] LoweredCodeUtils v2.4.6
 [23992714] MAT v0.10.7
 [3da0fdf6] MPIPreferences v0.1.11
 [1914dd2f] MacroTools v0.5.13
 [d125e4d3] ManualMemory v0.1.8
 [299715c1] MarchingCubes v0.1.9
 [d0879d2d] MarkdownAST v0.1.2
⌅ [a3b82374] MatrixFactorizations v2.2.0
 [bb5d69b7] MaybeInplace v0.1.2
 [739be429] MbedTLS v1.1.9
 [442fdcdd] Measures v0.3.2
 [e1d29d7a] Missings v1.2.0
 [46d2c3a1] MuladdMacro v0.2.4
 [bdf0d083] MultiFloats v2.0.2
 [ffc61752] Mustache v1.0.19
 [a975b10e] Mux v1.0.2
 [0db19996] NBInclude v2.3.0
 [85f8d34a] NCDatasets v0.14.4
 [d41bc354] NLSolversBase v7.8.3
 [2774e3e8] NLsolve v4.5.1 `https://github.com/PALEOtoolkit/NLsolve.jl#project_region`
 [77ba4419] NaNMath v1.0.2
 [8913a72c] NonlinearSolve v3.12.0
 [54ca160b] ODEInterface v0.5.0
 [09606e27] ODEInterfaceDiffEq v3.13.3
 [510215fc] Observables v0.5.5
 [6fe1bfb0] OffsetArrays v1.14.0
 [4d8831e6] OpenSSL v1.4.3
 [bac558e1] OrderedCollections v1.6.3
 [1dea7af3] OrdinaryDiffEq v6.78.0
 [673cec3b] PALEOaqchem v0.3.10
 [804b410e] PALEOboxes v0.21.26
 [4a6ed817] PALEOcopse v0.4.9
 [bf7b4fbe] PALEOmodel v0.15.42 `../../PALEOmodel.jl`
 [41de04b1] PALEOocean v0.4.4
 [bfd8b37b] PALEOreactions v0.21.10 `../PALEOreactions`
 [e0a37952] PALEOsediment v0.3.1
 [65ce6f38] PackageExtensionCompat v1.0.2
 [d96e819e] Parameters v0.12.3
 [69de0a69] Parsers v2.8.1
 [fa939f87] Pidfile v1.3.0
 [b98c9c47] Pipe v1.3.0
 [ccf2f8ad] PlotThemes v3.1.0
 [995b91a9] PlotUtils v1.4.1
 [a03496cd] PlotlyBase v0.8.19
 [f0f68f2c] PlotlyJS v0.18.13
 [f2990250] PlotlyKaleido v2.2.4
 [91a5bcdd] Plots v1.40.4
 [f517fe37] Polyester v0.7.14
 [1d0040c9] PolyesterWeave v0.2.1
 [2dfb63ee] PooledArrays v1.4.3
 [d236fae5] PreallocationTools v0.4.21
 [aea7be01] PrecompileTools v1.2.1
 [21216c6a] Preferences v1.4.3
 [08abe8d2] PrettyTables v2.3.1
 [c84ed2f1] Ratios v0.4.5
 [3cdcf5f2] RecipesBase v1.3.4
 [01d81517] RecipesPipeline v0.6.12
 [731186ca] RecursiveArrayTools v3.19.0
 [f2c3362d] RecursiveFactorization v0.2.23
 [189a3867] Reexport v1.2.2
 [2792f1a3] RegistryInstances v0.1.0
 [05181044] RelocatableFolders v1.0.1
 [ae029012] Requires v1.3.0
 [295af30f] Revise v3.5.14
 [f2b01f46] Roots v2.1.5
 [7e49a35a] RuntimeGeneratedFunctions v0.5.13
 [fdea26ae] SIMD v3.5.0
 [94e857df] SIMDTypes v0.1.0
 [476501e8] SLEEFPirates v0.6.42
 [0bca4576] SciMLBase v2.38.0
 [c0aeaf25] SciMLOperators v0.3.8
 [53ae85a6] SciMLStructures v1.2.0
 [6c6a2e73] Scratch v1.2.1
 [91c51154] SentinelArrays v1.4.3
 [efcf1570] Setfield v1.1.1
 [992d4aef] Showoff v1.0.3
 [777ac1f9] SimpleBufferStream v1.1.0
 [727e6d20] SimpleNonlinearSolve v1.8.0
 [699a6c99] SimpleTraits v0.9.4
 [ce78b400] SimpleUnPack v1.1.0
 [66db9d55] SnoopPrecompile v1.0.3
 [b85f4697] SoftGlobalScope v1.1.0
 [a2af1166] SortingAlgorithms v1.2.1
 [47a9eef4] SparseDiffTools v2.19.0
 [06eadbd4] SparsityTracing v0.2.5
 [e56a9233] Sparspak v0.3.9
 [276daf66] SpecialFunctions v2.4.0
 [aedffcd0] Static v0.8.10
 [0d7ed370] StaticArrayInterface v1.5.0
 [90137ffa] StaticArrays v1.9.4
 [1e83bf80] StaticArraysCore v1.4.2
 [82ae8749] StatsAPI v1.7.0
 [2913bbd2] StatsBase v0.34.3
 [7792a7ef] StrideArraysCore v0.5.6
 [69024149] StringEncodings v0.3.7
 [892a3eda] StringManipulation v0.3.4
 [09ab397b] StructArrays v0.6.18
 [c3572dad] Sundials v4.24.0
 [2efcf032] SymbolicIndexingInterface v0.3.21
 [3783bdb8] TableTraits v1.0.1
 [bd369af6] Tables v1.11.1
 [62fd8b95] TensorCore v0.1.1
 [1e6cf692] TestEnv v1.101.1
 [8290d209] ThreadingUtilities v0.5.2
 [a759f4b9] TimerOutputs v0.5.24
 [3bb67fe8] TranscodingStreams v0.10.8
 [d5829a12] TriangularSolve v0.2.0
 [410a4b4d] Tricks v0.1.8
 [781d530d] TruncatedStacktraces v1.4.0
 [5c2747f8] URIs v1.5.1
 [3a884ed6] UnPack v1.0.2
 [1cfade01] UnicodeFun v0.4.1
 [b8865327] UnicodePlots v3.6.4
 [1986cc42] Unitful v1.20.0
 [45397f5d] UnitfulLatexify v1.6.3
 [41fe7b60] Unzip v0.2.0
 [3d5dd08c] VectorizationBase v0.21.67
 [81def892] VersionParsing v1.3.0
 [19fa3120] VertexSafeGraphs v0.2.0
 [ea10d353] WeakRefStrings v1.4.2
 [0f1e0344] WebIO v0.8.21
 [104b5d7c] WebSockets v1.6.0
 [cc8bc4a8] Widgets v0.6.6
 [efce3f68] WoodburyMatrices v1.0.0
 [76eceee3] WorkerUtilities v1.6.1
 [fdbf4ff8] XLSX v0.10.1
 [ddb6d928] YAML v0.4.9
 [c2297ded] ZMQ v1.2.3
 [a5390f91] ZipFile v0.10.1
 [6e34b625] Bzip2_jll v1.0.8+1
 [83423d85] Cairo_jll v1.18.0+2
 [2702e6a9] EpollShim_jll v0.0.20230411+0
 [2e619515] Expat_jll v2.6.2+0
⌅ [b22a6f82] FFMPEG_jll v4.4.2+2
 [a3f928ae] Fontconfig_jll v2.13.96+0
 [d7e528f0] FreeType2_jll v2.13.2+0
 [559328eb] FriBidi_jll v1.0.14+0
 [0656b61e] GLFW_jll v3.3.9+0
 [d2c73de3] GR_jll v0.73.5+0
 [78b55507] Gettext_jll v0.21.0+0
⌃ [f8c6e375] Git_jll v2.36.1+2
 [7746bdde] Glib_jll v2.80.2+0
 [3b182d85] Graphite2_jll v1.3.14+0
⌅ [0234f1f7] HDF5_jll v1.12.2+2
 [2e76f6c2] HarfBuzz_jll v2.8.1+1
 [1d5cc7b8] IntelOpenMP_jll v2024.1.0+0
 [aacddb02] JpegTurbo_jll v3.0.3+0
 [f7e6163d] Kaleido_jll v0.2.1+0
 [c1c5ebd0] LAME_jll v3.100.2+0
⌅ [88015f11] LERC_jll v3.0.0+1
 [1d63c593] LLVMOpenMP_jll v15.0.7+0
 [aae0fff6] LSODA_jll v0.1.2+0
 [dd4b983a] LZO_jll v2.10.2+0
⌅ [e9f186c6] Libffi_jll v3.2.2+1
 [d4300ac3] Libgcrypt_jll v1.8.11+0
 [7e76a0d4] Libglvnd_jll v1.6.0+0
 [7add5ba3] Libgpg_error_jll v1.49.0+0
 [94ce4f54] Libiconv_jll v1.17.0+0
 [4b2f31a3] Libmount_jll v2.40.1+0
⌅ [89763e89] Libtiff_jll v4.5.1+1
 [38a345b3] Libuuid_jll v2.40.1+0
 [856f044c] MKL_jll v2024.1.0+0
⌃ [7243133f] NetCDF_jll v400.902.5+1
 [c771fb93] ODEInterface_jll v0.0.1+0
 [e7412a2a] Ogg_jll v1.3.5+1
⌅ [458c3c95] OpenSSL_jll v1.1.23+0
 [efe28fd5] OpenSpecFun_jll v0.5.5+0
 [91d4177d] Opus_jll v1.3.2+0
 [30392449] Pixman_jll v0.43.4+0
⌅ [c0090381] Qt6Base_jll v6.5.2+2
 [63e82ce6] SLEEF_jll v3.5.2+0
⌅ [fb77eaff] Sundials_jll v5.2.2+0
 [a44049a8] Vulkan_Loader_jll v1.3.243+0
 [a2964d1f] Wayland_jll v1.21.0+1
 [2381bf8a] Wayland_protocols_jll v1.31.0+0
 [02c8fc9c] XML2_jll v2.12.7+0
 [aed1982a] XSLT_jll v1.1.34+0
 [ffd25f8a] XZ_jll v5.4.6+0
 [f67eecfb] Xorg_libICE_jll v1.1.1+0
 [c834827a] Xorg_libSM_jll v1.2.4+0
 [4f6342f7] Xorg_libX11_jll v1.8.6+0
 [0c0b7dd1] Xorg_libXau_jll v1.0.11+0
 [935fb764] Xorg_libXcursor_jll v1.2.0+4
 [a3789734] Xorg_libXdmcp_jll v1.1.4+0
 [1082639a] Xorg_libXext_jll v1.3.6+0
 [d091e8ba] Xorg_libXfixes_jll v5.0.3+4
 [a51aa0fd] Xorg_libXi_jll v1.7.10+4
 [d1454406] Xorg_libXinerama_jll v1.1.4+4
 [ec84b674] Xorg_libXrandr_jll v1.5.2+4
 [ea2f1a96] Xorg_libXrender_jll v0.9.11+0
 [14d82f49] Xorg_libpthread_stubs_jll v0.1.1+0
 [c7cfdc94] Xorg_libxcb_jll v1.15.0+0
 [cc61e674] Xorg_libxkbfile_jll v1.1.2+0
 [e920d4aa] Xorg_xcb_util_cursor_jll v0.1.4+0
 [12413925] Xorg_xcb_util_image_jll v0.4.0+1
 [2def613f] Xorg_xcb_util_jll v0.4.0+1
 [975044d2] Xorg_xcb_util_keysyms_jll v0.4.0+1
 [0d47668e] Xorg_xcb_util_renderutil_jll v0.3.9+1
 [c22f9ab0] Xorg_xcb_util_wm_jll v0.4.1+1
 [35661453] Xorg_xkbcomp_jll v1.4.6+0
 [33bec58e] Xorg_xkeyboard_config_jll v2.39.0+0
 [c5fb5394] Xorg_xtrans_jll v1.5.0+0
 [8f1865be] ZeroMQ_jll v4.3.5+0
 [3161d3a3] Zstd_jll v1.5.6+0
 [35ca27e7] eudev_jll v3.2.9+0
⌅ [214eeab7] fzf_jll v0.43.0+0
 [1a1c6b14] gperf_jll v3.1.1+0
 [a4ae2306] libaom_jll v3.9.0+0
 [0ac62f75] libass_jll v0.15.1+0
 [2db6ffa8] libevdev_jll v1.11.0+0
 [f638f0a6] libfdk_aac_jll v2.0.2+0
 [36db933b] libinput_jll v1.18.0+0
 [b53b4c65] libpng_jll v1.6.43+1
 [a9144af2] libsodium_jll v1.0.20+0
 [f27f6e37] libvorbis_jll v1.3.7+1
 [009596ad] mtdev_jll v1.1.6+0
 [1317d2d5] oneTBB_jll v2021.12.0+0
 [1270edf5] x264_jll v2021.5.5+0
 [dfaa095f] x265_jll v3.5.0+0
 [d8fb68d0] xkbcommon_jll v1.4.1+1
 [0dad84c5] ArgTools v1.1.1
 [56f22d72] Artifacts
 [2a0f44e3] Base64
 [ade2ca70] Dates
 [8ba89e20] Distributed
 [f43a241f] Downloads v1.6.0
 [7b1f6079] FileWatching
 [9fa8497b] Future
 [b77e0a4c] InteractiveUtils
 [4af54fe1] LazyArtifacts
 [b27032c2] LibCURL v0.6.4
 [76f85450] LibGit2
 [8f399da3] Libdl
 [37e2e46d] LinearAlgebra
 [56ddb016] Logging
 [d6f4376e] Markdown
 [a63ad114] Mmap
 [ca575930] NetworkOptions v1.2.0
 [44cfe95a] Pkg v1.10.0
 [de0858da] Printf
 [9abbd945] Profile
 [3fa0cd96] REPL
 [9a3f8284] Random
 [ea8e919c] SHA v0.7.0
 [9e88b42a] Serialization
 [1a1011a3] SharedArrays
 [6462fe0b] Sockets
 [2f01184e] SparseArrays v1.10.0
 [10745b16] Statistics v1.10.0
 [4607b0f0] SuiteSparse
 [fa267f1f] TOML v1.0.3
 [a4e569a6] Tar v1.10.0
 [8dfed614] Test
 [cf7118a7] UUIDs
 [4ec0a83e] Unicode
 [e66e0078] CompilerSupportLibraries_jll v1.1.1+0
 [781609d7] GMP_jll v6.2.1+6
 [deac9b47] LibCURL_jll v8.4.0+0
 [e37daf67] LibGit2_jll v1.6.4+0
 [29816b5a] LibSSH2_jll v1.11.0+1
 [3a97d323] MPFR_jll v4.2.0+1
 [c8ffd9c3] MbedTLS_jll v2.28.2+1
 [14a3606d] MozillaCACerts_jll v2023.1.10
 [4536629a] OpenBLAS_jll v0.3.23+4
 [05823500] OpenLibm_jll v0.8.1+2
 [efcefdf7] PCRE2_jll v10.42.0+1
 [bea87d4a] SuiteSparse_jll v7.2.1+1
 [83775a58] Zlib_jll v1.2.13+1
 [8e850b90] libblastrampoline_jll v5.8.0+1
 [8e850ede] nghttp2_jll v1.52.0+1
 [3f19e933] p7zip_jll v17.4.0+2

Full output

In case of an error, please paste the full error message and stack trace.

[sjdaines]

Looking at the code,
https://github.com/Alexander-Barth/NCDatasets.jl/blob/354de308b31c27eac66f1de0ca37d0bad15147a7/src/netcdf_c.jl#L566C1-L577C1

this is intentional, so is this a netcdf limitation? (int64 is netcdf4 only, not available with netcdf3 https://docs.unidata.ucar.edu/nug/current/md_types.html)

(if so, perhaps should be added to Corner cases doc?)

[Alexander-Barth]

Yes, in NetCDF 3 and NetCDF 3 (classic format), Int64 are not supported and in the NetCDF CF convention prior to 1.9 they are not allowed.

https://cfconventions.org/Data/cf-conventions/cf-conventions-1.8/cf-conventions.html#_data_types
https://cfconventions.org/Data/cf-conventions/cf-conventions-1.9/cf-conventions.html#_data_types

Since CF 1.9 they are part of the standard. I agree that this should be documented, but I am also open to reconsider the current approach. Since Int64 is the default integer on many platforms, the potential of breaking code is unfortunately quite high.

Does your code, need to store integer larger than typemax(Int32) or it is rather the unexpected type change which is the issue?