GNU bug report logs - #15793
Bug: linking shared libraries on Cygwin results in undefined references to __stack_chck_guard for code compiled with -fstack-protector

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From: Richard PALO <richard <at> netbsd.org>
To: libtool-patches <at> gnu.org
Cc: 15793 <at> debbugs.gnu.org
Subject: bug#15793: Bug: linking shared libraries on Cygwin results in undefined references to __stack_chck_guard for code compiled with -fstack-protector
Date: Thu, 24 Sep 2015 15:15:57 +0200

[Message part 1 (text/plain, inline)]

Le 02/11/13 23:45, Richard PALO a écrit :
> Le 02/06/10 05:24, Yaakov (Cygwin/X) a écrit :
>> On Sat, 15 May 2010 09:07:49 +0200
>> Bart Van Assche <bvanassche <at> acm.org> wrote:
>>> This behavior has been observed with libtool version 2.2.6.
>>
>> Bug confirmed.  When code is compiled with -fstack-protector{,-all},
>> GCC "emits extra code to check for buffer overflows, such as stack
>> smashing attacks".  This extra code uses symbols from libssp, and
>> therefore (at least) Cygwin's GCC specs contain:
>>
>> *link_ssp:
>> %{fstack-protector|fstack-protector-all:-lssp_nonshared -lssp}
>>
>> Therefore, when libtool fails to pass -fstack-protector{,-all} at link
>> stage, the link fails.
>>
>> Patch attached.  (Yes, I have a copyright assignment on file.)
>>
>>
>> Yaakov
>> Cygwin/X
>>
> 
> I've done some limited testing of this patch on a SunOS distro with 
> pkgsrc, and it certainly helps a number of cases since it is gcc that 
> generates the necessary '-lssp_nonshared -lssp' libs for linking (at 
> least in absence of '-nostdlib').
> 
> Please include in the upcoming version.
> 
> 
> 
> 

I'd like to propose a slight modification this which, in addition, seems to get over the
issue (at least on solaris) of c++ shared libraries linking '-nostdlib'.  

This could easily be adapted for other hosts using g++. Note, it is harmless if '-dumpspecs'
or no spec with fstack-protector* is available.

It appears there was no warm welcome in tossing the '-nostdlib' setup for g++ shared libraries 
for solaris, so this seems to be a reasonable workaround.

-- 
Richard PALO

[0001-workaround-for-nostdlib-with-fstack-protector-on-sol.patch (text/x-patch, attachment)]

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