Re: Cyg32 on Win64 fails with stack-protector

[Ben RUBSON <ben dot rubson at gmail dot com>]

On 29 May 2018 18:59, Corinna Vinschen wrote:

> I suggest to build your own Cygwin and bisect it.

So I tried to bisect and had some difficulties.
I used a fresh 32 bits installation on a 64 bits system and followed this  
howto :
https://cygwin.com/faq/faq.html#faq.programming.building-cygwin

Prior to this commit : 6a848db44242a24d6570ef7994918c66ce483fd2
2017-11-29 - Yaakov Selkowitz - cygwin: export SSP functions
(which is the one JonY suspects)

With gcc 7.3, compilation fails with undefined __stack_chk_fail,  
__stack_chk_guard etc...
With gcc 6.4, compilation succeeds. Cygwin correctly starts with the new  
cygwin1.dll, but then, some programs, such as cmake (cmake --help) do not  
show any output anymore.
Same behavior using Cygwin snapshots. As it worked a few weeks ago, I tried  
to downgrade some runtime libraries, but with no luck.
This is easily reproductible, just install Cygwin32 on a 64-bits system,  
and select Cygwin 2.9 library instead of the 2.10 one.

So, unfortunately, I was not able to test any commit prior to the one given  
above.
This commit however correctly compiles with both gcc 6.4 and 7.3.
Cygwin correctly starts with it, program correctly show their output. And  
I'm able to reproduce the issue I opened this topic for.
So something important has changed between 2017-11-14 and 2017-11-29 which  
triggers this bug.

Perhaps the new SSP mechanism is more powerful than the previous one and  
triggers a long-time existing bug ?

Thank you again,

Ben