On Fri, May 11, 2018 at 9:47 PM, Zhang Qiang <dotslash...@gmail.com> wrote:
>
> Thanks for your valuable advice on debugging.
>
> The SysProcAttr field is nil, and I can't see why it fails from the
> strace, seems it just found the executable and then fails without
> doing fork:
>
> stat("/usr/bin/qemu-img", {st_mode=S_IFREG|0755, st_size=815784, ...}) = 0
> write(1, "SysProcAttr: <nil>", 18SysProcAttr: <nil>) = 18
> openat(AT_FDCWD, "/dev/null", O_RDONLY|O_CLOEXEC) = 7
> pipe2([8, 9], O_CLOEXEC) = 0
> pipe2([10, 11], O_CLOEXEC) = 0
> close(7) = 0
> close(9) = 0
> close(11) = 0
> close(8) = 0
> close(10) = 0
> write(1, "ret {\"status\":\"error\",\"error\":\"f"..., 79ret
> {"status":"error","error":"fork/exec /usr/bin/qemu-img: invalid
> argument"}
Thanks. That looks like the output from strace, not strace -f.
Ian
> On 12 May 2018 at 12:30, Ian Lance Taylor <i...@golang.org> wrote:
>> On Fri, May 11, 2018 at 8:36 PM, Tashi Lu <dotslash...@gmail.com> wrote:
>>>
>>> I faced a strange problem： os/exec always fails with `fork/exec
>>> /usr/bin/qemu-img: invalid argument'.
>>>
>>> Simplified code is at https://play.golang.org/p/v1APfzmS2p9. It seems this
>>> simplified snippet runs well without errors, but my real code is no more
>>> than just some variable initializations than this snippet. So I suspect it's
>>> the context's problem, but my context is too complex to simplify and put
>>> onto the playground. What I can think of that what might be linked to this
>>> error is that this function is run in a goroutine. But I did write a
>>> simplified goroutine version, sadly it worked well too... I had no idea how
>>> to do further debugging.
>>>
>>> And further, the executable is not to blame, it fails with the same error
>>> even if I substitute the executable to `ls' or anything else.
>>>
>>> Can you provide me some suggestions to the possible reason or the way to
>>> debug? Thanks.
>>
>> I would look first at the SysProcAttr field. Do you set that? Look
>> closely at the values.
>>
>> If that doesn't help, run your failing program under strace -f and
>> look for the failing system call.
>>
>> Ian
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