Fix GetTempFileName() on Windows

[danmoseley]

Fix #73793

1. Change from GetTempFileNameW to generating a random file with the same pattern we use on Unix - tmpXXXXXX.tmp.
2. Tweak an error string to make it more specific.

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.19044.1889 (21H2)
Intel Core i7-7700 CPU 3.60GHz (Kaby Lake), 1 CPU, 8 logical and 4 physical cores
.NET SDK=7.0.100-rc.2.22419.24
  [Host]     : .NET 7.0.0 (7.0.22.41112), X64 RyuJIT
  Job-SVOUAO : .NET 8.0.0 (42.42.42.42424), X64 RyuJIT
  Job-YORQJO : .NET 8.0.0 (42.42.42.42424), X64 RyuJIT

InvocationCount=1  UnrollFactor=1

|          Method |        Job |         Toolchain |     Mean |    Error |   StdDev |   Median | Ratio | RatioSD | Allocated |
|---------------- |----------- |------------------ |---------:|---------:|---------:|---------:|------:|--------:|----------:|
| GetTempFileName | Job-SVOUAO | \main\corerun.exe | 353.0 us | 21.81 us | 63.28 us | 343.2 us |  1.00 |    0.00 |         - |
| GetTempFileName | Job-YORQJO |   \pr\corerun.exe | 300.2 us | 17.85 us | 50.92 us | 279.3 us |  0.86 |    0.19 |         - |

That's with the best situation, where there's no existing temp files. When the temp folder is nearly full, the existing API deteriorates substantially:

|          Method |        Job |         Toolchain |        Mean |        Error |        StdDev |      Median | Ratio | RatioSD | Allocated |
|---------------- |----------- |------------------ |------------:|-------------:|--------------:|------------:|------:|--------:|----------:|
| GetTempFileName | Job-IBETAP | \main\corerun.exe | 94,514.5 us | 59,324.54 us | 160,387.33 us | 13,492.7 us |  1.00 |    0.00 |         - |
| GetTempFileName | Job-NDLNYW |   \pr\corerun.exe |    310.0 us |     16.70 us |      48.18 us |    297.4 us |  0.09 |    0.16 |         - |

This API will be hidden as part of #72881, but a great deal of code has been written to use it and that code will become faster/more robust. Incidentally, in testing this I filled up the temp folder and (with the previous implementation) Benchmark .NET crashed. That will now be fixed.

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Issue Details

---

Fix #73793

1. Change from GetTempFileNameW to generating a random file with the same pattern we use on Unix - tmpXXXXXX.tmp.
2. Tweak an error string to make it more specific.

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.19044.1889 (21H2)
Intel Core i7-7700 CPU 3.60GHz (Kaby Lake), 1 CPU, 8 logical and 4 physical cores
.NET SDK=7.0.100-rc.2.22419.24
  [Host]     : .NET 7.0.0 (7.0.22.41112), X64 RyuJIT
  Job-SVOUAO : .NET 8.0.0 (42.42.42.42424), X64 RyuJIT
  Job-YORQJO : .NET 8.0.0 (42.42.42.42424), X64 RyuJIT

InvocationCount=1  UnrollFactor=1

|          Method |        Job |         Toolchain |     Mean |    Error |   StdDev |   Median | Ratio | RatioSD | Allocated |
|---------------- |----------- |------------------ |---------:|---------:|---------:|---------:|------:|--------:|----------:|
| GetTempFileName | Job-SVOUAO | \main\corerun.exe | 353.0 us | 21.81 us | 63.28 us | 343.2 us |  1.00 |    0.00 |         - |
| GetTempFileName | Job-YORQJO |   \pr\corerun.exe | 300.2 us | 17.85 us | 50.92 us | 279.3 us |  0.86 |    0.19 |         - |

That's with the best situation, where there's no existing temp files. When the temp folder is nearly full, the existing API deteriorates substantially:

|          Method |        Job |         Toolchain |        Mean |        Error |        StdDev |      Median | Ratio | RatioSD | Allocated |
|---------------- |----------- |------------------ |------------:|-------------:|--------------:|------------:|------:|--------:|----------:|
| GetTempFileName | Job-IBETAP | \main\corerun.exe | 94,514.5 us | 59,324.54 us | 160,387.33 us | 13,492.7 us |  1.00 |    0.00 |         - |
| GetTempFileName | Job-NDLNYW |   \pr\corerun.exe |    310.0 us |     16.70 us |      48.18 us |    297.4 us |  0.09 |    0.16 |         - |

This API will be hidden as part of #72881, but a great deal of code has been written to use it and that code will become faster/more robust. Incidentally, in testing this I filled up the temp folder and (with the previous implementation) Benchmark .NET crashed. That will now be fixed.

Author:	danmoseley
Assignees:	danmoseley
Labels:	area-System.IO
Milestone:	-

[danmoseley]

Updated.

|          Method |        Job |         Toolchain |     Mean |   Error |  StdDev | Ratio | RatioSD | Allocated |
|---------------- |----------- |------------------ |---------:|--------:|--------:|------:|--------:|----------:|
| GetTempFileName | Job-FYMLRF | \main\corerun.exe | 362.1 us | 3.76 us | 3.33 us |  1.00 |    0.00 |     112 B |
| GetTempFileName | Job-VTFTPP |   \pr\corerun.exe | 341.6 us | 6.79 us | 9.06 us |  0.94 |    0.02 |     392 B |

for convenience, the above includes the cleanup: public string GetTempFileName() { string path = Path.GetTempFileName(); File.Delete(path); return path; }.

[danmoseley]

I think this is good to go. It does feel like this and GetTempFileName ideally would use 36 not 32 chars, giving another 4000 possibilities. I can change both if folks want. But 1 billion is a lot better than 65K.

[danmoseley]

Addressed feedback again.

[eerhardt]

LGTM. This is great. Now we can recommend using this API without having to add the caveat of "on Windows this is limited to 65K files".

We should also be sure to update the docs to remove that part for .NET 8:

https://docs.microsoft.com/en-us/dotnet/api/system.io.path.gettempfilename

The GetTempFileName method will raise an IOException if it is used to create more than 65535 files without deleting previous temporary files.

[danmoseley]

I think everything's addressed, unless you want me to remove the ToLowerInvariant.

[stephentoub]

I think everything's addressed, unless you want me to remove the ToLowerInvariant.

I mean, only if you care about saving the trees.

[danmoseley]

@stephentoub I noticed that GetTempFileName() on Unix throws FileNotFoundException when TMPDIR is bad. Windows throws DirectoryNotFoundException when TMP is bad. I fixed Unix - LMK if you have concerns. Perhaps a breaking change note to make.

where TMPDIR was /tmp/tmp7xcc3h.tmp/ it was Could not find file '/tmp/tmp7xcc3h.tmp/'. and it is now Could not find a part of the path '/tmp/tmp7xcc3h.tmp/'. with the correct DirectoryNotFoundException type.

[adamsitnik]

LGTM, thank you @danmoseley !

[danmoseley]

Failures are QUIC and LibrariesInteropGenerator