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Subject:	Re: [ANNOUNCEMENT] TEST RELEASE: Cygwin 2.10.0-0.1
To:	cygwin AT cygwin DOT com
References:	<announce DOT 20180116155108 DOT GA9503 AT calimero DOT vinschen DOT de> <9990d909-f112-9658-1b0f-d63e3f338a18 AT cornell DOT edu> <4f7edc68-4c98-8fa3-9fef-47bdd3343330 AT cornell DOT edu> <3b738a06-a3b8-210b-2886-4c9701efcd48 AT cygwin DOT com> <eb4e6cf2-12aa-bb4c-738e-f2259f58f3fe AT cornell DOT edu> <c5a92ae1-3b63-0227-f170-fa1d0ac959eb AT cornell DOT edu> <39045e32-8a2c-c767-0fcd-27d544ba6d93 AT cornell DOT edu>
From:	Ken Brown <kbrown AT cornell DOT edu>
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Date:	Sat, 20 Jan 2018 18:49:36 -0500
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On 1/20/2018 7:23 AM, Ken Brown wrote:
> On 1/19/2018 10:27 PM, Ken Brown wrote:
>> On 1/18/2018 6:28 PM, Ken Brown wrote:
>>> On 1/18/2018 4:30 PM, Yaakov Selkowitz wrote:
>>>> On 2018-01-18 08:35, Ken Brown wrote:
>>>>> On 1/17/2018 5:29 PM, Ken Brown wrote:
>>>>>> Do we need a new gcc release to go along with the recent ssp changes?
>>>>>
>>>>> The following commit message seems to answer my question:
>>>>>
>>>>>      Note that this does require building gcc with --disable-libssp 
>>>>> and
>>>>>      gcc_cv_libc_provides_ssp=yes.
>>>>
>>>> Correct.
>>>>
>>>>> Are there plans to coordinate the release of Cygwin 2.10.0 with a new
>>>>> gcc release?  In the meantime, I guess package maintainers have to 
>>>>> build
>>>>> with -U_FORTIFY_SOURCE in order to test building with Cygwin 
>>>>> 2.10.0.  Or
>>>>> am I missing something?
>>>>
>>>> -D_FORTIFY_SOURCE is not the default, so simply omitting it is
>>>> sufficient.
>>>
>>> I was talking about building projects in which _FORTIFY_SOURCE is 
>>> defined by default.  That happens, for instance, in the gnulib 
>>> subdirectory of the emacs tree, so it may affect other projects that 
>>> use gnulib also.
>>>
>>>> You could also just delete
>>>> /usr/lib/gcc/*-pc-cygwin/6.4.0/include/ssp, since we won't need it
>>>> anymore and it wasn't even being used properly in the first place.
>>>
>>> That's a simpler workaround than what I was doing.  Thanks.
>>
>> Here's another issue that's come up with _FORTIFY_SOURCE.  One of the 
>> emacs source files, fileio.c, makes use of a pointer to readlinkat. 
>> [More precisely, the file uses an external function foo() with a 
>> parameter 'bar' that's a pointer to a function; foo is called in 
>> fileio.c with bar = readlinkat.]
>>
>> When _FORTIFY_SOURCE > 0, this leads to an "undefined reference to 
>> `__ssp_protected_readlinkat'" linking error.  Does this sound like 
>> something that will be fixed with the new gcc release?
>>
>> I realize I haven't given you full details, but it might be a few days 
>> until I have a chance to extract an STC for this issue, so I thought 
>> I'd give it a shot.
>>
>> If you can't answer the question based on the information above, I'll 
>> make an STC as soon as I can.
> 
> I got to this sooner than expected:
> 
> $ cat ssp_test.c
> #define  _FORTIFY_SOURCE 1
> #include <unistd.h>
> void foo (ssize_t (*preadlinkat) (int, char const *, char *, size_t));
> 
> void baz ()
> {
>    foo (readlinkat);
> }
> 
> $ gcc -c -O1 ssp_test.c
> 
> $ objdump -x ssp_test.o | grep readlinkat
>    6 .rdata$.refptr.__ssp_protected_readlinkat 00000010 
> 0000000000000000  0000000000000000  00000180  2**4
> [...]

And the problem is still there with the new GCC that was just released.

Ken


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