[PATCH] Cygwin: pty: Fix 'Bad address' error when running 'cmd.exe /c dir'

[Johannes Schindelin]

Hi Takashi,

On Sat, 22 Oct 2022, Takashi Yano wrote:

> On Sat, 22 Oct 2022 07:58:37 +0200
> Johannes Schindelin wrote:
> > On October 22, 2022 7:34:20 AM GMT+02:00, Takashi Yano <takashi.yano@nifty.ne.jp> wrote:
> > >- If the command executed is 'cmd.exe /c [...]', runpath in spawn.cc
> > >  will be NULL. In this case, is_console_app(runpath) check causes
> > >  access violation. This case also the command executed is obviously
> > >  console app., therefore, treat it as console app to fix this issue.
> > >
> > >  Addresses: https://github.com/msys2/msys2-runtime/issues/108
> > >---
> > > winsup/cygwin/spawn.cc | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > >diff --git a/winsup/cygwin/spawn.cc b/winsup/cygwin/spawn.cc
> > >index 5aa52ab1e..4fc842a2b 100644
> > >--- a/winsup/cygwin/spawn.cc
> > >+++ b/winsup/cygwin/spawn.cc
> > >@@ -215,6 +215,8 @@ handle (int fd, bool writing)
> > > static bool
> > > is_console_app (WCHAR *filename)
> > > {
> > >+  if (filename == NULL)
> > >+    return true; /* The command executed is command.com or cmd.exe. */
> > >   HANDLE h;
> > >   const int id_offset = 92;
> > >   h = CreateFileW (filename, GENERIC_READ, FILE_SHARE_READ,
> >
> > The commit message of the original patch was substantially clearer and offered a thorough analysis. This patch lost that.
>
> The reason which I did not apply your patch as-is is:
> is_console_app() returns false for 'cmd.exe /c [...]' case
> with your patch, while it should return true.

Sure. And a simple "can you please modify the patch to return `true` in
the `cmd /c <command>` case" feedback would have avoided all the
contention.

Having said that, I fear that you completely misread what I wrote, as I
did not comment on your diff but on your quite improvable commit message.

Ciao,
Johannes