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CTRL-C event kills the application #205

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commented Jun 17, 2015

git-cmd.exe has a bad behavior when it receives CTRL-C event. A command line shell must handle the events.
For example, CTRL-C should be used to terminate the current command and not to terminate the shell himself.

When git-cmd.exe is launched, git-cmd.exe launches a child process (for example cmd.exe).
git-cmd.exe monitors the child process. When the child process exits, git-cmd.exe exits too.

When the user presses CTRL-C, the Windows console receives Windows messages for WM_KEYDOWN/WM_KEYUP.
Then the TranslateMessage function generates a CTRL-C event.

The CTRL-C event is handled by the Control Handler Function.
When a CTRL_BREAK_EVENT, CTRL_LOGOFF_EVENT, or CTRL_SHUTDOWN_EVENT signal is received, the control handler returns FALSE. Doing this causes the signal to be passed to the next control handler function. If no other control handlers have been registered or none of the registered handlers returns TRUE, the default handler will be used, resulting in the process being terminated.

cmd.exe Control Handler function terminates the current command and returns FALSE.
git-cmd.exe has no Control Handler Function registered. So git-cmd.exe is terminated.

When git-cmd.exe is used with programs like ConsoleZ, ConsoleZ injects a dll in git-cmd.exe and monitors this process.
When the user presses CTRL-C, git-cmd is terminated and so the ConsoleZ's tab is closed.

To fix this behavior, we can simply register a Control Handler function that returns TRUE (for all events). In this case the only way to exit this program is the launched command end.

Signed-off-by: Christophe Bucher Developer christophe.bucher@laposte.net

CTRL-C event kills the application
git-cmd.exe has a bad behavior when it receives CTRL-C event. A command line shell must handle the events.
For example, CTRL-C should be used to terminate the current command and not to terminate the shell himself.

When git-cmd.exe is launched, git-cmd.exe launches a child process (for example cmd.exe).
git-cmd.exe monitors the child process. When the child process exits, git-cmd.exe exits too.

When the user presses CTRL-C, the Windows console receives Windows messages for WM_KEYDOWN/WM_KEYUP.
Then the TranslateMessage function generates a CTRL-C event.

The CTRL-C event is handled by the Control Handler Function.
When a CTRL_BREAK_EVENT, CTRL_LOGOFF_EVENT, or CTRL_SHUTDOWN_EVENT signal is received, the control handler returns FALSE. Doing this causes the signal to be passed to the next control handler function. If no other control handlers have been registered or none of the registered handlers returns TRUE, the default handler will be used, resulting in the process being terminated.

cmd.exe Control Handler function terminates the current command and returns FALSE.
git-cmd.exe has no Control Handler Function registered. So git-cmd.exe is terminated.

When git-cmd.exe is used with programs like ConsoleZ, ConsoleZ injects a dll in git-cmd.exe and monitors this process.
When the user presses CTRL-C, git-cmd is terminated and so the ConsoleZ's tab is closed.

To fix this behavior, we can simply register a Control Handler function that returns TRUE (for all events). In this case the only way to exit this program is the launched command end.

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>

@cbucher cbucher referenced this pull request Jun 17, 2015

Closed

Proper support for Git 2 #230

@kjeremy kjeremy referenced this pull request Jun 17, 2015

Closed

Ctrl-C closes the console #192

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commented Jun 18, 2015

I've tested this patch, rebuilt mingw-w64-git using the 64 bit Git SDK, replaced the stock git-cmd.exe with the newly built one and it seems to fix the issue. No regressions so far.

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commented Jun 18, 2015

This is almost the solution I was looking for. I will reformat the commit message to make it comply with Git's standards, no need to worry about that.

The bigger worry is that there is a chance that we need to be able to disable the new behavior, most likely by introducing an appropriate command-line option. git-cmd.exe has to cater to more than just ConsoleZ.

I will still need to test whether everything is working alright (I could imagine that Ctrl+C is no longer handled correctly when trying to interrupt a runaway executable spitting out millions of lines).

However, I tested that the current git-cmd.exe, i.e. the one without this patch works correctly when I double-click it in the Explorer and press Ctrl+C.

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commented Jun 18, 2015

However, I tested that the current git-cmd.exe, i.e. the one without this patch works correctly when I double-click it in the Explorer and press Ctrl+C.

@dscho I hope you do realize that git-cmd.exe on its own was never an issue. The issue is with git-cmd.exe --command=usr\bin\bash.exe --login -i.

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commented Jun 18, 2015

I hope you do realize that git-cmd.exe on its own was never an issue. The issue is with git-cmd.exe --command=usr\bin\bash.exe --login -i.

I just created a shortcut, launched it, and it still does exactly what I want it to do: if I press Ctrl+C at the Bash prompt, it cancels the current command line and gives me a new one. If I run cat and press Ctrl+C, that program is interrupted. Even if I run git rev-list HEAD -- which is a Win32 executable, not an MSys2 one -- and press Ctrl+C, that program is interrupted as well.

So yes, I think I realize how you run git-cmd. It's just that doing so outside of ConsoleZ seems to work without any problem.

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commented Jun 18, 2015

@dscho press Win+R (Run command), start git-cmd.exe --command=usr\bin\bash.exe --login -i, press Ctrl+C, and check out your taskmgr, git-cmd will be gone, even tho your prompt will be retained.

Press Win+R, start cmd.exe, git-cmd.exe --command=usr\bin\bash.exe --login -i from within CMD, press Ctrl+C twice, and on top of git-cmd being gone, you'll only get More ? messages upon keypresses.

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commented Jun 18, 2015

Unfortunately, my concerns were legitimate: if I run the patches git-cmd.exe and try to interrupt a long-running git rev-list HEAD, it simply freezes. With no way to recover other than calling the Task Manager, guessing the correct git.exe and terminating the process (with two frightening warnings).

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commented Jun 18, 2015

press Win+R (Run command), start git-cmd.exe --command=usr\bin\bash.exe --login -i

FWIW I get the exact same freezing behavior with the patches git-cmd.exe when I call it that way rather than via a newly-created shortcut.

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commented Jun 18, 2015

@bviktor @cbucher as I do not have ConsoleZ, could you please test whether you also experience the freezing behavior?

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commented Jun 18, 2015

@dscho sure, just give me a repo and the exact command you're running :)

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commented Jun 18, 2015

Actually, I've found a very simple way of triggering freezes: just start git-cmd.exe --command=usr\bin\bash.exe --login -i and press Ctrl+C continuously. It will freeze within a second.

Here's the funny thing: if you let it run for like a minute, it'll eventually return the prompt and even display what you've typed during the freeze.

Note: this only happens with git-cmd.exe --command=usr\bin\bash.exe --login -i. The standard git-cmd.exe or git-bash.exe won't trigger this.

Now the bad news: this happens both with and without the patch, so I'm not quite sure the freeze you encountered was caused by the patch, it may have always been present... I assume you don't usually invoke the shell with git-cmd.exe --command=usr\bin\bash.exe --login -i (especially since --command is a very new feature) so it could be that you simply haven't faced the issue earlier.

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commented Jun 18, 2015

@cbucher I could imagine that something like this is what you actually need:

diff --git a/compat/win32/git-wrapper.c b/compat/win32/git-wrapper.c
index 396a4ee..27b7777 100644
--- a/compat/win32/git-wrapper.c
+++ b/compat/win32/git-wrapper.c
@@ -535,6 +535,8 @@ int main(void)
            si.dwFlags |= STARTF_USESHOWWINDOW;
            si.wShowWindow = SW_SHOW;
        }
+       if (wait)
+           creation_flags |= CREATE_NEW_PROCESS_GROUP;
        br = CreateProcess(/* module: null means use command line */
                exep,
                cmd,  /* modified command line */
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commented Jun 18, 2015

@dscho for me all the difference this patch makes is that the first freeze kicks in after like 10 seconds instead of just 1. After that, additional freezes again take just 1 second.

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commented Jun 21, 2015

RC3 introduced the redirectors. This means that I can use just bin\bash.exe --login -i and git commands will still be available.

Now the funny thing is that even tho git-cmd.exe is no longer involved,

  • Ctrl+C still closes the tab in ConsoleZ
  • two consecutive Ctrl+C presses still produce More ? messages when started from CMD
  • it still won't close upon Ctrl+C when started via Win+R, but then spamming Ctrl+C still causes freezes

So basically, bin\bash.exe --login -i produces the exact same symptoms as git-cmd.exe --command=usr\bin\bash.exe --login -i. Yeesh.

So after all, it may not be git-cmd's fault at all. At this point, it seems more like a bash problem.

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commented Jun 21, 2015

So after all, it may not be git-cmd's fault at all. At this point, it seems more like a bash problem.

No, it is still the Git wrapper's problem (or ConsoleZ's, still unsure), because the redirector is simply an adapted copy of the Git wrapper, just like git-cmd.exe, except that it executes a different command-line by default.

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commented Jun 21, 2015

@bviktor did you have a chance to test the CREATE_NEW_PROCESS_GROUP idea yet?

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commented Jun 21, 2015

@bviktor did you have a chance to test the CREATE_NEW_PROCESS_GROUP idea yet?

Sure, I already tried that.

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commented Jun 22, 2015

Hmm. This makes me believe that there is another, completely separate issue going on there, that is not helped by the ctrl handler nor the new process group?

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commented Jun 22, 2015

Should I open a separate ticket about Ctrl+C spam freezing?

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commented Jun 22, 2015

@bviktor I think this should be a separate ticket, because the symptom is already different, therefore I suspect the cause to be different, too.

If this still happens even with the ctrl handler patch of @cbucher, I strongly suspect that it is a ConsoleZ issue, either. In any case, it will require quite a lot of effort to figure out, I am afraid.

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commented Jun 22, 2015

I strongly suspect that it is a ConsoleZ issue

ConsoleZ issue for an issue you can reproduce without ConsoleZ?!?
ahem...

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commented Jun 22, 2015

Lol, I believe it was a typo :D

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commented Jun 22, 2015

I strongly suspect that it is a ConsoleZ issue

ConsoleZ issue for an issue you can reproduce without ConsoleZ?!?
ahem...

Well, given that I cannot reproduce that freeze after 10 seconds, I assume that it is a ConsoleZ issue.

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commented Jun 22, 2015

@dscho this happens with standard Git2, zero ConsoleZ involved. But I'll have to check it on a Win8 comp, too. If you can't repro, this may be Win10-specific then. I'll let you know in a new ticket.

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commented Jun 22, 2015

@cbucher BTW I think that we should introduce a new command-line option to install that ctrl handler and not do that by default, seeing as it would cause problems with MinTTY if we do so. I trust you agree that this is a good compromise.

@bviktor I cannot reproduce. Git2, zero ConsoleZ. No freeze. I also got that exact same behavior on 8.1, 7 and XP.

dscho pushed a commit that referenced this pull request Aug 13, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho pushed a commit that referenced this pull request Aug 13, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho pushed a commit that referenced this pull request Aug 15, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho pushed a commit that referenced this pull request Aug 15, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho added a commit that referenced this pull request Aug 15, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho added a commit that referenced this pull request Aug 15, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho pushed a commit that referenced this pull request Aug 20, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho pushed a commit that referenced this pull request Aug 20, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho added a commit that referenced this pull request Aug 22, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho added a commit that referenced this pull request Aug 22, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho added a commit that referenced this pull request Aug 22, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho pushed a commit that referenced this pull request Aug 25, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho pushed a commit that referenced this pull request Aug 25, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho added a commit that referenced this pull request Aug 25, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho pushed a commit that referenced this pull request Aug 26, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho pushed a commit that referenced this pull request Aug 26, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho pushed a commit that referenced this pull request Aug 27, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho added a commit that referenced this pull request Aug 28, 2016

git-wrapper: do not let the Ctrl-C event kill the wrapper
... while waiting for the child process to finish.

The Git wrapper serves, among other things, as git-cmd.exe. In that
role, its primary purpose is to provide an interactive cmd window that
knows where to find Git.

A secondary use of git-cmd.exe is to be able to launch other console
processes that know about Git, e.g. when ConsoleZ wants to call an
interactive Bash (it cannot call git-bash.exe because that would open a
new MinTTY window). To this end, git-cmd.exe supports the --command=...
command-line option. The interactive bash would be called like this:

	git-cmd --command=usr\bin\bash.exe -l -i

The command-line arguments after the --command=... options are simply
passed through to the command itself. If no --command=... option is
specified, git-cmd.exe defaults to cmd.exe.

Once git-cmd.exe is launched, it finds the top-level directory of the
Git for Windows installation and then launches the command as a child
process. And this is where things get a little bit tricky: When the user
presses CTRL-C, the cmd window receives WM_KEYDOWN/WM_KEYUP messages
which are then handled by the TranslateMessage function that generates a
CTRL-C event that is sent to the console processes running in the
console window (i.e. both git-cmd.exe and the child process).

If no Console Ctrl Handlers have been registered, the git-cmd.exe
process will simply be terminated, without having waited for the
interactive Bash to quit (it does not quit, of course, because it
handles Ctrl+C by terminating any process launched from within the
Bash). Now both cmd and the Bash compete for user input.

Luckily, the solution is very easy: the Win32 API sports a
SetConsoleCtrlHandler() function to register/unregister Console Ctrl
Handlers. When the NULL pointer is registered as "handler", it "causes
the calling process to ignore CTRL+C input":

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686016.aspx

This is exactly what we need here: while waiting for the child processes
to finish, the git-cmd.exe process itself should not be interruptible by
the user. Immediately after the child process terminates, we unregister
the Console Ctrl Handler.

Note: we need to be careful with changes to the Git wrapper as it serves
many other purposes in addition to git-cmd.exe. For example, it serves
as the cmd\git.exe as well as all of the git-<builtin>.exe stand-ins.
So do we want the same Ctrl+C behavior even in those instances? Yes: If
the user interrupts using Ctrl+C, the child process should terminate
before the Git wrapper.

Also note: We cannot override the Console Ctrl Handler with a function
that simply always returns TRUE: this would prevent the console window
opened via git-cmd.exe from closing, since the Console Ctrl Handler
*also* handles "signals generated by the system when the user closes the
console, logs off, or shuts down the system."

[jes: changed the patch to conform with the surrounding coding style, to
pass NULL as Console Ctrl Handler and unregister it as soon as
appropriate, fixed commit message to be more accurate and informative,
added link to the SetConsoleCtrlHandler() documentation.]

This fixes #205

Signed-off-by: Christophe Bucher Developer <christophe.bucher@laposte.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

@Eugeny Eugeny referenced this pull request Feb 17, 2019

Closed

Ctrl+c close the tab #596

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