Question on statically linking with cygwin

[Johannes Thoma]

Hi Jon, Hi Martin,

Thanks for your answer, comments inline:

Am 16.10.23 um 17:28 schrieb Jon Turney:
> On 22/09/2023 12:12, Johannes Thoma via Cygwin wrote:
>> Hi Martin,
>>
>> Thanks for your answer, comments inline:
>>
>> Am 22.09.23 um 07:54 schrieb Martin Wege via Cygwin:
>>> On Tue, Sep 19, 2023 at 5:24 PM Johannes Thoma via Cygwin
>>> <cygwin@cygwin.com> wrote:
>>>>
>>>> Hi,
>>>>
>>>> As I understood the reason for not being able to statically link
>>>> the cygwin1.dll in to a binary and distribute that is because of
>>>> licensing issues.
>>>
>>> Do you have any references for that?
>> I read that in the Cygwin FAQ:
>>
>> https://cygwin.com/faq/faq.html#faq.programming.static-linking
>>
>> I read through the licensing options and IMHO linking statically
>> against cygwin (which is GPL) from a program (like WinDRBD) that
>> is also GPL should be allowed. But I am not a lawyer ...
> 
> That FAQ probably needs clarifying.
> 
> The two sentences are probably intended to be taken separately.
> 
> So, to be clear, there are technical reasons why the cygwin DLL is not also made available as a static library.
> 
>>>> Are there any technical issues that would make
>>>> it impossible to link with cygwin statically?
>>>>
>>>> The reason I am asking is I am working on a GPL project
>>>> (WinDRBD: https://github.com/LINBIT/windrbd) and am currently
>>>> delivering the cygwin1.dll along with the binary. It would be
>>>> desireable to have the cygwin1.dll statically linked (for example
>>>> to avoid version clashes) instead. Is that technically possible?
>>>> If necessary I am ready to compile cygwin (at least the needed
>>>> files) on my own.
>>>
>>> Interesting.
>>> But how (from a developers perspective) do you link cygwin1.dll
>>> statically into a binary?
>>>
>> I would build my own cygwin1.lib or cygwin1.a and statically link
>> against it.
> 
> If you do work out how to do this, patches would be welcome...
> 
You are right it is far from trivial. I am working on it, not
sure now if it will be possible or how long it takes (my main
project is WinDRBD, so unfortunately I cannot spend full time on
getting static linking work). Right now, I can compile cygwin on my own
and digged a little bit in the program startup code (lib subdir),
I will keep you updated once I go along.

Best regards,

- Johannes