Re: dynamic conpty loading

Hi Thomas,

On Thu, 27 Nov 2025 17:52:33 +0100
Thomas Wolff wrote:
> Am 27.11.2025 um 15:04 schrieb Takashi Yano via Cygwin:
> > On Thu, 27 Nov 2025 17:20:26 +0900
> > Takashi Yano wrote:
> >> On Wed, 26 Nov 2025 19:50:07 +0100
> >> Thomas Wolff wrote:
> >>> Am 26.11.2025 um 11:32 schrieb Takashi Yano via Cygwin:
> >>>> On Fri, 21 Nov 2025 17:58:01 +0100
> >>>> Thomas Wolff wrote:
> >>>>
> >>>>> Am 21.11.2025 um 17:46 schrieb Corinna Vinschen via Cygwin:
> >>>>>> Hi Thomas,
> >>>>>>
> >>>>>> On Nov 21 16:46, Thomas Wolff via Cygwin wrote:
> >>>>>>> Am 21.11.2025 um 11:04 schrieb Takashi Yano via Cygwin:
> >>>>>>>> On Sun, 5 Oct 2025 10:15:55 +0200
> >>>>>>>> Thomas Wolff wrote:
> >>>>>>>>>>> The procedure seems to be:
> >>>>>>>>>>> try LoadLibrary("conpty.dll"), (if not successful, fallback to
> >>>>>>>>>>> GetModuleHandle("kernel32") instead) to retrieve GetProcAddress for
> >>>>>>>>>>> CreatePseudoConsole, ResizePseudoConsole, ClosePseudoConsole, and
> >>>>>>>>>>> then somehow (?) use those while calling CreateProcess.
> >>>>>>>>>>> The latter is woven into the cygwin library and I don't think it's a
> >>>>>>>>>>> good idea to clone that out of cygwin for a patched process creation
> >>>>>>>>>>> in mintty.
> >>>>>>>>>>>
> >>>>>>>>>>> My question/suggestion:
> >>>>>>>>>>> Can a cygwin mode switch to a selected conpty library instead of the
> >>>>>>>>>>> default one please?
> >>>>>> Where do you expect this conpty.dll to reside?
> >>>>>>
> >>>>>> If we do something like that, I would suggest to make sure that this
> >>>>>> conpty.dll is in a well-defined place. /bin or /lib might be a good
> >>>>>> idea. And if it exists in this defined place, it will be used by Cygwin.
> >>>>>>
> >>>>>> We can tweak the autoload mechanism to allow a primary DLL and a fallback
> >>>>>> DLL, that drops the need to set the CYWIN env var.
> >>>>>>
> >>>>>> The mintty package could contain a post-install script, or some other
> >>>>>> script in /bin to allow a user with admin rights downloading the latest
> >>>>>> (or the most sensible) conpty.dll from MSFT.
> >>>>>>
> >>>>>> Would that make sense?
> >>>>>>
> >>>>>>
> >>>>>> Corinna
> >>>>>>
> >>>>> That makes much sense, yes, thank you. /bin/conpty.dll would probably be
> >>>>> a good place.
> >>>> I checked the source of conpty.dll
> >>>> https://github.com/microsoft/terminal/blob/main/src/winconpty/winconpty.cpp
> >>>>
> >>>> conpty.dll seems to launch OpenConsole.exe in the directory where
> >>>> WindowsTerminal is installed.
> >>>> However, BUILTIN\Users does not have permission to execute OpenConsole.exe.
> >>>>
> >>>> Do you have some idea how to solve this problem?
> >>>> WindowsTerminal itself can launch OpenConsole.exe, so there should be
> >>>> some solutions, I think.
> >>> Did you install the nuget package? It can be extracted with zip, so you
> >>> can install OpenConsole as a normal program...
> >>> I did not find a way, though, to invoke it explicitly so that it would
> >>> solve the pty interworking problems.
> >> Thanks.
> >>
> >> I've made an experimental patch against fhandler/pty.cc and
> >> draft package named openconsole that installs official OpenConsole.exe
> >> binary into /usr/bin.
> >>
> >> I confirmed the patch with openconsole package enables the mouse
> >> support for vim91 and neovim 0.8.0 (native windows binary) in
> >> pseudo console.
> >>
> >> Any comments and suggestions would be appreciated.
> > openconsole-1.23.12811.0-1.cygwin.patch fixed.
> Thanks, I've tried to build latest newlib-cygwin with the 0001-... patch 
> but then I'm getting this:
> 
>        0 [main] bash 27975 child_copy: dll data read copy failed, 
> 0x7FFA4C7CE000..0x7FFA4C7E7C90, done 0, windows pid 22444, Win32 error 299
>                                                                   0 
> [main] -bash 27950 dofork: child -1 - forked process 22444 died 
> unexpectedly, retry 0, exit code 0xC0000005, errno 11
>                          -bash: fork: retry: Resource temporarily 
> unavailable

Thanks for testing.
When do you get the error above?

In my environment, the patch works under Win11/Win10 with and without
OpenConsole.exe installed.

Win32 error 299 is ERROR_PARTIAL_COPY, so child_copy copied only
partially some reason. However, I don't change any code path for
native cygwin program with this patch. Therefore, I believe the
patch does not affect fork().

-- 
Takashi Yano <[email protected]>

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