[wasi] Implement MksTemps/MkdTemp so GetTempFileName and CreateTempSubdirectory work by lewing · Pull Request #134958 · dotnet/runtime

lewing · 2026-09-30T16:28:57Z

wasi-libc provides neither mkstemps/mkstemp nor mkdtemp. So on WASI, SystemNative_MksTemps asserted and returned -1 without setting errno, and SystemNative_MkdTemp returned NULL the same way. As a result, Path.GetTempFileName threw IOException : Success : '/tmp/', and Directory.CreateTempSubdirectory was also broken. The temp directory itself works fine; the only missing piece was creating a unique name in it.

Change

src/native/libs/System.Native/pal_io.c, WASI only. This mirrors how libc implements these functions:

GetTempNameRandomChars validates the template. It requires six X characters immediately before the suffix and otherwise fails with errno = EINVAL.
FillTempNameRandomChars fills the XXXXXX from getentropy (backed by wasi:random), mapped to [A-Za-z0-9].
SystemNative_MksTemps loops up to 100 times calling open(path, O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0600). It returns the fd on success, retries on EEXIST, and returns -1 with errno preserved on any other error. If every attempt collides, it fails with errno = EEXIST.
SystemNative_MkdTemp runs the same loop with mkdir(path, 0700). It returns the template on success and NULL with errno set on failure.

Non-WASI native code paths are unchanged. The WASI preprocessor branch also uses defined(TARGET_WASI). Because this lives in the shared System.Native, the fix applies to both CoreCLR and Mono on WASI.

After #134813 merged, this branch was rebased onto upstream main fa693c42fb6. It removes all 89 WASI ActiveIssue attributes against #134943 across 24 test files, preserving other attributes, comments, and test code.

Removing the class-wide configuration quarantine exposed a separate missing-user-profile failure. Only ConfigurationTests.TouchingFileWillReloadForUserSecrets remains quarantined on WASI, now against #135225. No harness defaults or unrelated product code change in this PR.

Validation after rebase and quarantine removal

Local macOS arm64 host, wasi-sdk 34, wasmtime via XHarness, CoreCLR WASI interpreter (not ReadyToRun). The worktree-local tool-cache override avoids modifying a concurrently used checkout.

The product command below passed with 0 warnings and 0 errors. Initially the existing CMake caches retained SDK-33 compiler paths despite selecting the SDK-34 toolchain and failed to link WASI networking symbols. Clearing only this worktree's generated WASI CoreCLR/native object directories resolved the mismatch; no source workaround was used.

export DOTNET_WASM_TOOL_CACHE_DIR="$PWD/.dotnet/wasm-tools"
./build.sh -os wasi -arch wasm -rf CoreCLR -s clr+libs+host+packs -c Release
./dotnet.sh build src/libraries/Microsoft.Extensions.Configuration.FileExtensions/tests/Microsoft.Extensions.Configuration.FileExtensions.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
./dotnet.sh build src/libraries/Microsoft.Extensions.Configuration/tests/FunctionalTests/Microsoft.Extensions.Configuration.Functional.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
./dotnet.sh build src/libraries/Microsoft.VisualBasic.Core/tests/Microsoft.VisualBasic.Core.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
./dotnet.sh build src/libraries/System.CodeDom/tests/System.CodeDom.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
./dotnet.sh build src/libraries/System.ComponentModel.Composition/tests/System.ComponentModel.Composition.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
./dotnet.sh build src/libraries/System.Data.Common/tests/System.Data.Common.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
./dotnet.sh build src/libraries/System.Diagnostics.TextWriterTraceListener/tests/System.Diagnostics.TextWriterTraceListener.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
./dotnet.sh build src/libraries/System.Memory.Data/tests/System.Memory.Data.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
./dotnet.sh build src/libraries/System.Private.Xml/tests/System.Private.Xml.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
./dotnet.sh build src/libraries/System.Reflection.Metadata/tests/System.Reflection.Metadata.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
./dotnet.sh build src/libraries/System.Runtime.Loader/tests/RefEmitLoadContext/System.Runtime.Loader.RefEmitLoadContext.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
WasmXHarnessMonoArgs='--env=DOTNET_CI=true' ./dotnet.sh build src/libraries/System.Runtime/tests/System.IO.Tests/System.IO.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release
./dotnet.sh build src/libraries/System.ServiceModel.Syndication/tests/System.ServiceModel.Syndication.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release

All commands above exited 0. Counts were checked in the runner logs and xUnit XML:

Suite	Run	Passed	Skipped
Microsoft.Extensions.Configuration.FileExtensions.Tests	20	20	0
Microsoft.Extensions.Configuration.Functional.Tests	32	29	3
Microsoft.VisualBasic.Core.Tests	22,219	22,215	4
System.CodeDom.Tests	5,982	5,977	5
System.ComponentModel.Composition.Tests	1,431	1,426	5
System.Data.Common.Tests	11,717	11,708	9
System.Diagnostics.TextWriterTraceListener.Tests	132	130	2
System.Memory.Data.Tests	87	81	6
System.Private.Xml.Tests	48,626	48,558	68
System.Reflection.Metadata.Tests	880	869	11
System.Runtime.Loader.RefEmitLoadContext.Tests	1	1	0
System.IO.Tests	3,019	2,963	56
System.ServiceModel.Syndication.Tests	1,323	1,323	0
Total	95,469	95,300	169

System.ComponentModel.Composition.Tests was exercised in the interpreter lane, even though it is excluded from the trimmed WASI R2R lane (#135045).

Two initial-run findings:

Configuration Functional initially reported 33 run, 29 passed, 1 failed, 3 skipped: the missing HOME failure now tracked in [wasi] Library tests have no HOME/user profile (user secrets path) #135225. A diagnostic re-run of the unquarantined bundle with guest HOME=/tmp reported 33 run, 30 passed, 0 failed, 3 skipped. The final normal-environment run after the method-only quarantine reported the 32-test result above; 27 tests in ConfigurationTests still passed.
System.IO initially reported 3,020 run, 2,963 passed, 1 failed, 56 skipped, solely in the unchanged MemoryStream_CapacityBoundaryChecks large-allocation test. That test already carries SkipOnCI; forwarding the existing CI guest setting DOTNET_CI=true reproduces the interpreter CI lane and gives the passing result above. No new MemoryStream quarantine was added, and all eight re-enabled StreamReader/StreamWriter temporary-file cases passed.

Original before/after reproduction

Before the test-standup merge, on the SDK-33 baseline:

./build.sh -os wasi -arch wasm -rf CoreCLR -s clr+libs -c Release
./build.sh -os wasi -arch wasm -rf CoreCLR -s libs.native -c Release
./dotnet.sh build src/libraries/System.Memory.Data/tests/System.Memory.Data.Tests.csproj /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release /p:TargetFramework=net11.0

The product build passed with zero warnings/errors. Stashing the native fix, rebuilding libs.native, and running Memory.Data reproduced 87 run, 80 passed, 1 failed, 6 skipped (BinaryDataTests.CanCreateBinaryDataFromFileStream: IOException : Success : '/tmp/'). Restoring the fix, rebuilding libs.native, and repeating the same test command passed: 87 run, 81 passed, 0 failed, 6 skipped.

The per-app wasihost links libSystem.Native.a from the runtime pack, so the rebuilt library is what the tests use.

System.Runtime.Extensions.Tests (PathTests.GetTempFileName) and System.IO.FileSystem.Tests (Directory_CreateTempSubdirectory) do not target WASI (-windows;-unix;-browser only), so they were not run. Mono WASI and the ReadyToRun lane were not run.

Resolves #134943

Note

This PR was authored with assistance from GitHub Copilot.

azure-pipelines · 2026-09-30T16:29:46Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

dotnet-policy-service · 2026-09-30T16:30:08Z

Tagging subscribers to this area: @dotnet/area-system-io
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dotnet-policy-service · 2026-09-30T16:31:38Z

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
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Path.GetTempFileName/Directory.CreateTempSubdirectory fail because MksTemps/MkdTemp are stubbed (dotnet#134943, fix in dotnet#134958), and File.Copy fails because fchmod returns ENOSYS (dotnet#134944, fix in dotnet#134959). Quarantine at class level where the test constructor fails and at method level otherwise, so the lanes can go green before the fixes merge. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

) The CoreCLR WASI host (`wasihost`) initializes the runtime with only `TRUSTED_PLATFORM_ASSEMBLIES`, `APP_PATHS` and the host runtime contract. It never reads the app's runtime configuration, so none of the `configProperties` from `<app>.runtimeconfig.json` reach `AppContext`: feature switches, `RuntimeHostConfigurationOption` items and so on. For example, `System.Text.Encoding.EnableUnsafeUTF7Encoding` never arrives, so UTF-7 tests throw `NotSupportedException : Support for UTF-7 is disabled`. When trimming, `System.Data.DataSet.XmlSerializationIsSupported` is seen as missing by test `PlatformDetection`. ## Change - `src/native/corehost/wasihost/wasihost.cpp`: read `runtimeconfig.bin` from next to the entry assembly and append its properties to the init properties passed to `coreclr_initialize`. Properties the host sets itself take precedence. `get_runtime_property` already serves from the same vectors, so the contract callback returns the same values. A missing file is ignored, and a malformed one fails startup with a message. - `src/mono/wasi/build/WasiApp.CoreCLR.targets`: copy `runtimeconfig.bin` into `managed/`, next to the entry assembly, the framework, `icudt.dat` and the host. `WasiAppBuilder` places it at the bundle root, which `run-wasmtime.sh` (`cd managed && wasmtime --dir . ...`) does not preopen. `runtimeconfig.bin` is the file `RuntimeConfigParserTask` already produces for WASI apps, and Mono's WASI driver consumes the same file. Its format is an ECMA-335 compressed count followed by key/value serialized strings, so the host needs no JSON parser. The browser CoreCLR host follows the same model: `configProperties` first, with host-set properties overriding them. ## Validation Local, macOS arm64 host, wasi-sdk 33, wasmtime 45. - `./build.sh -os wasi -arch wasm -rf CoreCLR -s clr+libs+host -c Release` on clean upstream `main` → succeeded, 0 warnings, 0 errors. - `./build.sh -os wasi -arch wasm -rf CoreCLR -s host.native -c Release` with the change → succeeded; `wasihost.cpp` compiles with no warnings. **System.Text.Encoding.Tests** (untrimmed, `./dotnet.sh build src/libraries/System.Runtime/tests/System.Text.Encoding.Tests/System.Text.Encoding.Tests.csproj -f net11.0 /t:Test /p:TargetOS=wasi /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Release`) On `main`, the full suite hangs in `TranscodingStreamTests.ReadAsync_LoopsWhenPartialDataReceived`, a blocking wait on single-threaded WASI that is handled in #134813. So I compared the UTF-7-related classes directly with wasmtime on the bundle (`-class` for EncodingMiscTests, EncodingGetEncodingTest, NegativeEncodingTests and the seven `UTF7Encoding*` classes): | | Tests run | Passed | Failed | |---|---|---|---| | Without fix | 1692 | 1654 | **38** (all `Support for UTF-7 is disabled`) | | With fix | 1720 | 1720 | **0** | Full suite with the fix, with the hanging test skipped locally only (not part of this PR): 14614 run, 14605 passed, 4 failed, 5 skipped, 0 UTF-7 failures. The 4 failures are unrelated: `FromUtf16Tests`/`ToUtf16Tests.SomeNonAsciiInput` need System.Security.Cryptography (#99126), and `TranscodingStreamTests.ReadApm`/`WriteApm` throw `PlatformNotSupportedException` from `TaskToAsyncResult.Begin`. **System.Data.Common.Tests** (untrimmed, same command with the System.Data.Common.Tests project) - With fix: 11734 run, 11658 passed, 67 failed, 9 skipped. The same bundle run with `managed/runtimeconfig.bin` removed, which reproduces the pre-fix behavior, gives the identical 67 failures. So there are no regressions. 54 of the failures are `IOException : Success : '/tmp/'` (#134958), and the rest are DbProviderFactories and serialization-guard failures unrelated to runtimeconfig. - The DataSet switch only lands in runtimeconfig when trimming, and trimmed CoreCLR-WASI test builds don't work on `main` yet (ILLink can't resolve System.Private.CoreLib; #134813 sets that up). To confirm the switch now reaches both the product and `PlatformDetection`, I added `System.Data.DataSet.XmlSerializationIsSupported=false` to the bundle's `runtimeconfig.bin` and ran `-class System.Data.Tests.DataSetTest -class System.Data.Tests.DataTableTest5`. The original config gave 63 run, 48 passed, 14 failed (`/tmp`), 1 skipped. With the switch it gave 63 run, 44 passed, 0 failed, 19 skipped: the guarded tests skip and nothing fails from a product/test mismatch. This is split out from the WASI R2R test-standup work in #134813, where the missing properties account for the 38 UTF-7 failures and about 360 System.Data.Common failures in trimmed runs. Resolves #134954 > [!NOTE] > This PR was authored with assistance from GitHub Copilot. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Path.GetTempFileName/Directory.CreateTempSubdirectory fail because MksTemps/MkdTemp are stubbed (dotnet#134943, fix in dotnet#134958), and File.Copy fails because fchmod returns ENOSYS (dotnet#134944, fix in dotnet#134959). Quarantine at class level where the test constructor fails and at method level otherwise, so the lanes can go green before the fixes merge. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

jkotas · 2026-10-05T14:47:10Z

Re-enable tests disabled against #134943

wasi-libc provides neither mkstemp(s) nor mkdtemp, so on WASI these entry points were stubbed out and returned failure without setting errno. This made Path.GetTempFileName throw "IOException : Success : '/tmp/'" and broke Directory.CreateTempSubdirectory. Emulate them the way libc does: validate the template, fill the trailing XXXXXX from getentropy mapped to [A-Za-z0-9], and create the entry with open(O_CREAT|O_EXCL) / mkdir, retrying on EEXIST a bounded number of times. errno is set on every failure path. Non-WASI code paths are unchanged. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Remove all 89 WASI quarantines against issue 134943 after the MksTemps/MkdTemp fix. Preserve unrelated attributes and test code. Keep only the independently failing user-secrets reload test quarantined against issue 135225; the rest of ConfigurationTests now runs on WASI. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

lewing · 2026-10-06T09:25:23Z

filed #135268 for the error

lewing · 2026-10-06T09:27:19Z

/azp run runtime-coreclr outerloop

azure-pipelines · 2026-10-06T09:27:39Z

Azure Pipelines: Successfully started running 1 pipeline(s).

lewing · 2026-10-06T15:15:08Z

/ba-g unrelated failures are filed

github-actions Bot added the area-System.IO label Sep 30, 2026

lewing added arch-wasm WebAssembly architecture os-wasi Related to WASI variant of arch-wasm labels Sep 30, 2026

lewing requested review from pavelsavara and radekdoulik September 30, 2026 16:31

dotnet-policy-service Bot assigned lewing Sep 30, 2026

lewing mentioned this pull request Sep 30, 2026

[wasi] Pass runtimeconfig properties to the runtime in wasihost #134964

Merged

build-analysis Bot mentioned this pull request Sep 30, 2026

Error while retrieving client Settings for PipelineArtifact. HttpRequestException: nodename nor servname provided, or not known (vsblobprodcus3.vsblob.visualstudio.com:443) #96798

Open

lewing marked this pull request as ready for review October 2, 2026 01:46

build-analysis Bot mentioned this pull request Oct 2, 2026

[ci-scan] Test failure: HandleEventShutdownInitiatedByTransport fails with QuicException : The connection timed out from inactivity. #133373

Open

lewing mentioned this pull request Oct 5, 2026

[wasi] Library tests have no HOME/user profile (user secrets path) #135225

Open

lewing force-pushed the lewing-wasi-mkstemps-fix branch from 3515dd0 to 0e71660 Compare October 5, 2026 15:45

lewing mentioned this pull request Oct 6, 2026

[ci-scan] Test failure: System.Net.Http.Functional.Tests.SocketsHttpHandlerTest_HttpClientHandlerTest_Http3.LargeUriAndHeaders_Works #135268

Open

lewing requested a review from akoeplinger October 6, 2026 09:25

pavelsavara approved these changes Oct 6, 2026

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This was referenced Oct 6, 2026

[ci-scan] Test failure: profiler runtimeasyncapis crashes (Abort trap: 6, exit 133) on interpreter osx-arm64 #133006

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tracing\eventpipe\reverse test failing with EndOfStreamException #134280

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lewing merged commit d0e41cb into dotnet:main Oct 6, 2026
170 of 174 checks passed

dotnet-maestro Bot mentioned this pull request Oct 7, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#10016

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[wasi] Implement MksTemps/MkdTemp so GetTempFileName and CreateTempSubdirectory work - #134958

[wasi] Implement MksTemps/MkdTemp so GetTempFileName and CreateTempSubdirectory work#134958
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Validation after rebase and quarantine removal

Original before/after reproduction

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