RE: Regression in Cygwin 3.2.0

[David Allsopp <David.Allsopp@cl.cam.ac.uk>]

Thomas Wolff wrote:
> Am 16.04.2021 um 12:17 schrieb David Allsopp via Cygwin:
> > I'm unable to build OCaml using the mingw-w64 compilers with Cygwin
> > 3.2.0. Windows 10.0.19042.928 (and tried on three different machines
> > so far)
> >
> > Repro:
> >
> >   - Fresh Cygwin64 installation with make, libiconv,
> > mingw64-x86_64-gcc-core and git added; fire up mintty
> >   - git clone --depth 1 --recursive https://github.com/ocaml/ocaml
> >   - cd ocaml && ./configure --host=x86_64-w64-mingw32 && make -j8
> > flexdll && make -j8 world.opt
> >
> > This is consistently hanging with Cygwin 3.2.0 and seems possibly to
> > have something to do with linking (the creation of
> > runtime/ocamlrun.exe and stdlib/camlheader, which is also an
> > executable, seem to be part of the problem).
> >
> > It can be immediately fixed by downgrading to Cygwin 3.1.7, cleaning
> > the tree and repeating the build.
> >
> > I'm of course very happy to try to reduce this to a smaller repro
> > case, but is there an obvious culprit in Cygwin 3.2.0 to check before I
> > do?
> The build fails for me with error messages but it does not hang.

Thanks for confirming!

> You could have tried at least building without -j option, and running the
> build steps separately for better diagnostics.

Indeed - the repro case above was intended to be small and fast. I was still
at the "is this just me/us", stage. Suggesting a non-parallel build of OCaml
would have been mean, as it takes about an hour if it doesn't crash...!

That said, the non-parallel build I think reveals the Cygwin problem: there
are console windows constantly flashing up (it renders the workstation
unusable for the duration of the build). The first stage of the build
compiles ocamlrun.exe which is non-Cygwin in this case and then it uses
that throughout the build, so I guess it's the conpty changes which are biting.

However, the build did succeed when run without -j, however this (which will
take about 20 mins or so):

./configure --build=x86_64-w64-mingw32 --disable-native-compiler
make flexdll runtop

causes a new console Window to pop up with an OCaml prompt (which can be quit
by taking #quit;;) rather than the same prompt being connected to mintty.

With make -j, it doesn't appear to flash up all the console Windows, but it's
also reliably failing. I tried with the cygwin1.dll snapshot from this morning
which seems to be doing the same.


David