Return nil when openFifo returns nil #47
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The return statement in the OpenFifo wrapper function implicitly boxes the *fifo pointer into an io.ReadWriteCloser interface value, even when the value is (*fifo)(nil). It is the same gotcha described in https://go.dev/doc/faq#nil_error and causes the same sorts of confusing situations. Modify the OpenFifo wrapper function to return a nil interface value when openFifo returns a nil pointer value. Signed-off-by: Cory Snider <[email protected]>
corhere
commented
Nov 8, 2022
| @@ -42,15 +42,16 @@ func TestFifoCancel(t *testing.T) { | |||
| leakCheckWg = nil | |||
| }() | |||
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| _, err = OpenFifo(context.Background(), filepath.Join(tmpdir, "f0"), syscall.O_RDONLY|syscall.O_NONBLOCK, 0600) | |||
| f, err := OpenFifo(context.Background(), filepath.Join(tmpdir, "f0"), syscall.O_RDONLY|syscall.O_NONBLOCK, 0600) | |||
| assert.Exactly(t, nil, f) | |||
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Annoyingly, assert.Nil considers non-nil interface values which contain nil concrete values to be nil values despite those values being != nil.
AkihiroSuda
approved these changes
Nov 8, 2022
cpuguy83
approved these changes
Nov 8, 2022
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Oh! Saw the PR title and had to think of #32, but I see you linked that above, nice 👍 |
thaJeztah
reviewed
Nov 8, 2022
| assert.NotNil(t, err) | ||
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| assert.NoError(t, checkWgDone(leakCheckWg)) | ||
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| ctx, cancel := context.WithTimeout(context.Background(), 500*time.Millisecond) | ||
| defer cancel() | ||
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| f, err := OpenFifo(ctx, filepath.Join(tmpdir, "f0"), syscall.O_RDONLY|syscall.O_CREAT|syscall.O_NONBLOCK, 0600) | ||
| f, err = OpenFifo(ctx, filepath.Join(tmpdir, "f0"), syscall.O_RDONLY|syscall.O_CREAT|syscall.O_NONBLOCK, 0600) |
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Oh! Not a blocker (at all), but if you want to reduce code-churn, perhaps reformat the octal values to the new format (0o600) while updating these lines
This was referenced Feb 21, 2023
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The return statement in the
OpenFifowrapper function implicitly boxes the*fifopointer into anio.ReadWriteCloserinterface value, even when the value is(*fifo)(nil). It is the same gotcha described in https://go.dev/doc/faq#nil_error and causes the same sorts of confusing situations. Modify theOpenFifowrapper function to return anilinterface value whenopenFiforeturns anilpointer value.(*fifo)(nil)value could escape the package, and therefore the root cause of SIGSEGV dockerd 20.10.2 docker/for-linux#1186 for which fifo.Close(): prevent possible panic if fifo is nil #32 was added as a workaround.