Re: Uninitialized structure in printing functions

[Giacomo Tesio <giacomo at tesio dot it>]

Sorry, I've just noticed that -O0 was not enough: I also configured
newlib with --disable-newlib-fwrite-in-streamio actually removing the
uio structures altogether.

Neither -O0 nor --disable-newlib-fwrite-in-streamio were enough alone.
They are needed together to make the hello world test pass.


Giacomo



2017-04-27 16:10 GMT+02:00 Giacomo Tesio <giacomo@tesio.it>:
> Hi, I've just found that with -O0 both my tests and the newlib's
> testsuite work as expected, even removing the uio initialization
> provided in the patch.
>
> This is a bit weird. My cross compiler is GCC 4.9.4: is it possible
> that newlib is not actually tested with this version?
>
>
> Giacomo
>
> 2017-04-26 11:35 GMT+02:00 Giacomo Tesio <giacomo@tesio.it>:
>> Hi Corinna,
>>
>> I was trying to fix a simple "hello, world" test:
>> https://github.com/JehanneOS/jehanne/blob/c2982db8a2c57a3250c129c28bb395715521ec4e/qa/lib/newlib/hello.c.
>>
>> During debug one of the issue I've noticed was a fault related to uio
>> in vfprintf.c:348: apparently uio->uio_resid was uninitialized and
>> actually the patch I provided fixed the test.
>> However with a different test I'm working on now, I've found that
>> zeroing the structures is not enough.
>> Somehow uio->uio_resid overflows there, but I wasn't able yet to
>> identify why or where.
>>
>> Any suggestion is welcome. I supposed I've just hit an untested
>> combination of configure options, but actually --enable-newlib-mb is
>> the only configure option I'm using (except for prefix and target,
>> obviously).
>>
>>
>>
>> Giacomo
>>
>>
>> 2017-04-26 10:24 GMT+02:00 Corinna Vinschen <vinschen@redhat.com>:
>>> On Apr 21 19:03, Giacomo Tesio wrote:
>>>> Hi, during the port to Jehanne, I had issues with the uninitialized
>>>> uio structure in several printing functions.
>>>>
>>>> The attached patch fixes them.
>>>
>>> I'm puzzled what problem you're solving.
>>>
>>> I inspected the code in question and the uio structure is always filled
>>> with values for all three members before using it.  Setting uio to 0
>>> in all these places looks gratuitous.
>>>
>>> Can you please explain what exactly you're observing and how setting
>>> uio to all 0 solved this problem?
>>>
>>>
>>> Corinna
>>>
>>> --
>>> Corinna Vinschen
>>> Cygwin Maintainer
>>> Red Hat