bug#45518: Ctrl-G Fails to Interrupt Hung Tramp Remote-Compile in Emacs 27.1

[Duncan Greatwood <dgbulk@gmail.com>]

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Michael -

On Wed, Jan 6, 2021 at 5:37 AM Michael Albinus <michael.albinus@gmx.de>
wrote:

> Duncan Greatwood <dgbulk@gmail.com> writes:
>
> Hi Duncan,
>
> > I would suggest that you take a favorite large C++ autotools project,
> > add test.cpp to the source tree and Makefile.am, and see if the hang
> > reproduces for you.
>
> I don't work with C++, so I haven't.
>
[DG] Oh, no worries. Let me try and give a more explicit recipe.

This is what I did:

Download the autotools "hello world" program, and modify it as follows.

Go to https://github.com/shanecelis/amhello (or *many* other places), and
download the "hello world" code (click Code button on the github page,
choose "Download zip" for simplicity).

Expand the zip file, and cd into amhello-master directory. This is on a
linux machine, an ubuntu machine in my case.

Open configure.ac in a text editor. You'll see a section headed:
    # Checks for programs.
We need to add AC_PROG_CXX and AM_PROG_AR, so this section will look like:
    # Checks for programs.

    AC_PROG_CC
    AC_PROG_CXX
    AM_PROG_AR
    AC_PROG_LIBTOOL
Save configure.ac, and exit the text editor.

Copy my test.cpp file into the src subdirectory of amhello-master.

Open src/Makefile.am in a text editor.
Added test.cpp to the sources line, so that line looks like:
    hello_SOURCES = main.c test.cpp
Save src/Makefile.am and exit the editor.

I presume you already have the autotools toolset installed, but if not,
install them.
    sudo apt-get install -y autotools-dev autoconf

Now at the shell command line (*not* in emacs) on the target linux machine,
in the amhello-master directory:
    autoreconf --install
    ./configure
    make

You should see the many syntax errors of test.cpp spewing out in the shell.

Now *in gui emacs*, from a mac machine using Tramp,
open amhello-master/src/test.cpp remotely (using tramp) on the remote linux
machine.
With that remote test.cpp open, In emacs, do
    M-compile
    Use the compile command: make -k

Tramp window hangs

As you noted prior, if you use compile command "gcc test.cpp", tramp does
not hang. Only if you use compile command "make" does it hang.

I was using my macbook laptop for the GUI-emacs-with-tramp, and ubuntu for
the target linux machine. I was using emacs 26.2 gui-mode, but no reason to
suppose it varies with other emacs versions.

I did try it with a Linux laptop, running emacs-gui (26.3) and tramp to
connect to the remote Linux host. However, in that case the issue did *not*
reproduce for me, at least using this method. Perhaps emacs/tramp must be
running from a mac for the issue to show up.

Hope this helps.
Thanks once more.
Duncan



>
> > For your reference, I am also pasting the output from the hung tramp
> > window when I added test.cpp to a library within one of my own larger
> > projects.
>
> I tried to mimic that, but it still just shows all errors, and no hung
> window. Tested with recent Tramp 2.5.0 and all Emacs versions 26, 27,
> 28. See appended compile output.
>
> > Regards,
> > D.
>
> Best regards, Michael.

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