On Thu, Dec 22, 2016 at 11:40 AM, Andrii Kroitor <an.kroi...@samsung.com> wrote:
> On 22.12.16 15:00, Gustavo Sverzut Barbieri wrote:
>> On Thu, Dec 22, 2016 at 10:27 AM, Andrii Kroitor <an.kroi...@samsung.com>
>> wrote:
>>> lorddrew pushed a commit to branch master.
>>>
>>> http://git.enlightenment.org/core/efl.git/commit/?id=11e687578dca47f024dc230f2d23c579ddd91961
>>>
>>> commit 11e687578dca47f024dc230f2d23c579ddd91961
>>> Author: Andrii Kroitor <an.kroi...@samsung.com>
>>> Date: Thu Dec 22 14:10:10 2016 +0200
>>>
>>> ecore_exe: fix send on Windows
>>>
>>> Check for bytes written only if more than 0 bytes were sent.
>>> I don't know why some efl code is trying to send 0 bytes, but that
>>> works on
>>> Linux and therefore should be fixed on Windows.
>>> ---
>>> src/lib/ecore/ecore_exe_win32.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/src/lib/ecore/ecore_exe_win32.c
>>> b/src/lib/ecore/ecore_exe_win32.c
>>> index 305298e..3532fe1 100644
>>> --- a/src/lib/ecore/ecore_exe_win32.c
>>> +++ b/src/lib/ecore/ecore_exe_win32.c
>>> @@ -560,7 +560,7 @@ _impl_ecore_exe_send(Ecore_Exe *obj,
>>> BOOL res;
>>>
>>> res = WriteFile(exe->pipe_write.child_pipe_x, data, size, &num_exe,
>>> NULL);
>>> - if (!res || num_exe == 0)
>>> + if (size && !res || num_exe == 0)
>> eventually apps don't check what they try to send... but the library
>> should, then don't try to send, the WriteFile with zero-size is not
>> right.
>>
> I've experimented with adding abort() on sending zero bytes and this
> leads to segfault on `elementary_test -to Thumb` on Linux.
> So EFL code itself is actually trying to send 0 bytes to child process.
> I'm wondering is there any reason to do this on Linux?
I bet it's a bug in upper layers. But we shouldn't try to write zero
bytes. Also, see the Linux manpage write(2):
If count is zero and fd refers to a regular file, then write() may
return a failure status if one of the errors below is detected. If no
errors are detected, or error detection is not performed, 0 will be
returned without causing any other effect. If count is zero and fd
refers to a file other than a regular file, the results are not speci‐
fied.
We're talking about non-regular file, thus the second case, which
means unspecified.
TL;DR: before WriteFile() or write() we should check:
EINA_SAFETY_ON_TRUE_RETURN_VAL(size == 0, ...);
--
Gustavo Sverzut Barbieri
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