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Fix macOS dir behaviour by providing EINTR handling #48694

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Merged
merged 3 commits into from
Feb 25, 2021
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Fix macOS dir behaviour by providing EINTR handling #48694

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Fix macOS dir behaviour by providing EINTR handling
Therzok Feb 24, 2021
89605a0
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Therzok Feb 24, 2021
82fa411
Use errno instead of error for looping.
Therzok Feb 25, 2021
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24 changes: 21 additions & 3 deletions src/libraries/Native/Unix/System.Native/pal_io.c
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Original file line number Diff line number Diff line change
Expand Up @@ -427,7 +427,10 @@ int32_t SystemNative_ReadDirR(DIR* dir, uint8_t* buffer, int32_t bufferSize, Dir
return errno == 0 ? -1 : errno;
}
#else
int error = readdir_r(dir, entry, &result);
int error;

// EINTR isn't documented, happens in practice on macOS.
while ((error = readdir_r(dir, entry, &result)) && error == EINTR);
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are you sure the EINTR is returned as the return value and not in errno?

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@Therzok Therzok Feb 25, 2021 •
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I don't have a reliable repro, but I can look in xnu source. I can adapt it so it checks errno.

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Seems like readdir_r sets the return value to whatever is in errno?

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I've read a few man pages of different OSes and there seems to be little consistency regarding this.
If using errno works on macOS then I'd prefer that since it's what we use everywhere else.

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I've changed it.

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If using errno works on macOS then I'd prefer that since it's what we use everywhere else.

Except this API explicitly says errors are returned rather than surfacing through errno. Is there an example man page that says readdir_r sets errno? What happens if a readdir_r implementation doesn't touch errno at all, errno retains an EINTR value from prior to the readdir_r call, and readdir_r hits another error... might we end up in an infinite loop?

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I can change the code back to checking the return code :D

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Before you do, I'd like to hear from @akoeplinger :) I was actually asking questions rather than stating things that must happen ;-)

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Specifically, on macOS/FreeBSD, it looks like this: https://opensource.apple.com/source/Libc/Libc-1439.40.11/gen/FreeBSD/readdir.c.auto.html


// positive error number returned -> failure
if (error != 0)
Expand Down Expand Up @@ -473,12 +476,27 @@ int32_t SystemNative_ReadDirR(DIR* dir, uint8_t* buffer, int32_t bufferSize, Dir

DIR* SystemNative_OpenDir(const char* path)
{
return opendir(path);
DIR *result;

// EINTR isn't documented, happens in practice on macOS.
while ((result = opendir(path)) == NULL && errno == EINTR);

return result;
}

int32_t SystemNative_CloseDir(DIR* dir)
{
return closedir(dir);
int32_t result;

result = closedir(dir);

// EINTR isn't documented, happens in practice on macOS.
if (result < 0 && errno == EINTR)
{
result = 0;
}

return result;
}

int32_t SystemNative_Pipe(int32_t pipeFds[2], int32_t flags)
Expand Down