Codestin Search App

Shablone · 2025-09-01T21:33:16Z

Dynamic Console Allocation for Windows

Purpose

Windows GUI builds either always show a short console pupup on windows systemstart implementation or never show one (CLI users can't see output).
See PR10334 , PR926 and many more

Solution

Implement dynamic console allocation:

No console when double-clicked from Explorer
Console appears when launched with CLI arguments
--no-console flag to explicitly disable console
Console behavior preserved across monitor restarts

Testing

syncthing.exe              # No console (GUI)
syncthing.exe --help       # Shows console + help
syncthing.exe --no-console # No console even with args

Opening from explorer won't show a console.

Implementation

Uses Windows API (AllocConsole/AttachConsole) to create console on demand
Monitor process passes --no-console to child processes when appropriate
Windows-only using build constraints

Fixes console window appearing briefly when launched from Explorer while maintaining proper CLI functionality.

Authorship

Name: Elias @Shablone
Email: [email protected]

rafaeloledo · 2025-09-01T22:15:34Z

Did you have success running it?

rasa · 2025-09-02T03:55:32Z

cmd/syncthing/monitor.go

 	}
+
+	// Check if --no-console was passed or if we have no args (double-clicked)
+	noConsole := len(args) <= 1 // No args means launched from GUI


noConsole := slices.Contains(args, "--no-console")

rasa · 2025-09-02T03:56:30Z

cmd/syncthing/monitor.go

+	childArgs := args[1:] // Start with original args (excluding binary name)
+	if noConsole {
+		// Check if --no-console is already in the args
+		hasNoConsole := false


hasNoConsole := slices.Contains(childArgs, "--no-console")

rasa · 2025-09-02T04:03:33Z

cmd/syncthing/console_windows.go

+	procFreeConsole      = kernel32.NewProc("FreeConsole")
+	procGetConsoleWindow = kernel32.NewProc("GetConsoleWindow")
+	procSetStdHandle     = kernel32.NewProc("SetStdHandle")
+	procCreateFileW      = kernel32.NewProc("CreateFileW")


CreateFile and SetStdHandle are in sys/x/windows

lib/osutil/console_windows.go

rasa · 2025-09-02T04:07:47Z

cmd/syncthing/console_windows.go

+		return nil // No command line arguments, don't allocate console
+	}
+
+	// Check if --no-console flag is present


if slices.Contains(os.Args[1:], "--no-console") {
return nil
}

(Prefer if they actually used the arguments parser we have...)

rasa · 2025-09-02T04:17:26Z

One issue with this is if a user runs this GUI version from inside an SSH session, they won't see any output. The console window will appear on the desktop.

calmh

This is the approach that we didn't get to work previously. If it does work, i.e. behaves reasonably in a normal terminal etc, that's cool. I don't see why you're reinventing command line parsing multiple times instead of using the parsed command line though?

Shablone · 2025-09-02T15:37:44Z

Thank you for the review :)
I will rework that changes accordingly.

I was reinventing the stuff because

It was late
I'm not familiar with Go
I didn't get familiar with the remaining codebase
Sorry for that

I will also investigate the ssh session. Although it seems very niche to me, to ssh into a windows server.

calmh · 2025-09-02T15:38:28Z

I think the SSH bit is indeed extremely niche, but probably follows the same scenario as just running the command in an existing cmd? At least the latter should work, imho. (by which I mean "show output in that terminal")

calmh · 2025-09-02T20:03:51Z

This seems somewhat promising. I'll have comments on the actual code and stuff at some point, but just some behavioural notes;

When doubleclicking syncthing.exe from explorer, there is a console flash but it disappears. That's good, but even better if it were possible to avoid the flash? If not, no biggie, it's already at the same level as the old --no-console was while it worked.
This is possibly an extension for a future PR but, currently, if Syncthing is already running and is then doubleclicked again, visually nothing happens (except the flash as above). I think it would be nice and make sense if it resulted in the equivalent of synchthing.exe browser, i.e. start the UI. (Perhaps that's not on you and should just be the default behavior when launching Syncthing a second time under any platform and circumstance. Something to think about.)

Shablone · 2025-09-02T20:10:30Z

I noticed that syncthing not only was starting in console mode, it also opened the browser at runtime via calling cmd.exe resulting in another flash if no console was present yet.
I included the fix here
I haven't checked, but I guess this was the reason for your mentioned scenario @calmh

Shablone · 2025-09-15T14:51:19Z

Hey
I'm not sure if I just need to be patient, but is there anything missing for a merge?

tomasz1986 · 2025-09-15T16:19:45Z

I'm trying to test the PR right now, but for me, even when launched from Explorer, the console window just stays open.

This is under Windows 10 x64, and the default shell is set to Command Prompt.

calmh

Some structural notes

calmh · 2025-09-15T16:37:38Z

cmd/syncthing/console_windows.go

+	}
+
+	// User explicitly disabled console  -> don't allocate console
+	if slices.Contains(os.Args[1:], "--no-console") {


I see no reason to do this instead of using our command line parser? (If there is one it's fine, but requires explanation. If it's about having a console available for when --help gets called, I suspect there is a way around that using the binding callback on the --no-console option perhaps...)

calmh · 2025-09-15T16:38:06Z

cmd/syncthing/console_windows.go

+		return nil
+	}
+
+	// SSH sessions -> don't allocate console


Why not, what happens otherwise?

calmh · 2025-09-15T16:41:06Z

cmd/syncthing/console_windows.go

+	// Try to attach to parent consol
+	if ret, _, err := procAttachConsole.Call(uintptr(ATTACH_PARENT_PROCESS)); ret != 0 {
+		return redirectStdHandles()
+	} else if err != syscall.Errno(0) {


This should probably be !errors.Is(err, syscall.Errno(0)) and errors.As below instead of the direct case

calmh · 2025-09-15T16:41:23Z

cmd/syncthing/console_windows.go

+	if ret, _, err := procAllocConsole.Call(); ret != 0 {
+		consoleAllocated = true
+		return redirectStdHandles()
+	} else if err != syscall.Errno(0) {


calmh · 2025-09-15T16:46:01Z

cmd/syncthing/console_windows.go

+
+// FreeConsole releases the console
+func FreeConsole() {
+	if consoleAllocated {


I'd rather see this as a return value from InitConsole, to avoid keeping the global around...

Signed-off-by: Elias <[email protected]>

Shablone · 2025-09-28T20:57:12Z

Alright. Please have another look

I now splitted the console initialization into attachment (Already on present) and allocation (a new one needed).
Relying on Kong would otherwise be very complex. The console handle should already be there if --help was passed or some invalid arguments. Unfortunately both don't reach Kongs AfterApply(). I also can't use the other hooks of kong, as they wouldn't have parsed the arguments yet.
But I like the new approach better then the manual flag check. So now I always try to to attach to a console if present. Then we can parse the arguments and only create a new console if needed.

I also tested the ssh stuff. With the current commit when I ssh from unix into windows and call synthing.exe, it will pipe the output to my ssh shell. No new console appears 👍

I also learned that FreeConsole() is not needed, as windows this stuff on its own on process termination. So I could delete the defering stuff

I removed the old HideConsole and replaced it with the dynamic allowcation

Shablone · 2025-09-28T20:59:34Z

Please keep in mind, that for testing there should be no newer version online, which does not have this feature implemented. Or auto-upgrade should be disabled.
Otherwise it will upgrade itself and run as console again

calmh · 2025-10-01T21:56:28Z

cmd/syncthing/openurl_windows.go

+// 2. cmd.exe /C start (fallback): Traditional approach that spawns a command
+//    shell. Less secure (potential command injection) but works on all Windows
+//    versions including very old ones.


I'm pretty sure we don't run on those Windows versions...

Signed-off-by: Elias <[email protected]>

calmh

Thanks, sorry for taking some time on this, I do want to get it in. Can you sort out the various style/linter complaints please, and then I think this is ready given it passes some manual testing 🙏

calmh · 2025-10-21T06:12:12Z

cmd/syncthing/main.go

+	var consoleAttached = false
+	if err := osutil.AttachConsole(); err == nil {
+		consoleAttached = true
+	}


Suggested change

var consoleAttached = false

if err := osutil.AttachConsole(); err == nil {

consoleAttached = true

}

consoleAttached := osutil.AttachConsole() == nil

if we don't care about the error, I guess

Signed-off-by: Elias <[email protected]>

Shablone · 2025-10-21T18:53:21Z

Thanks, sorry for taking some time on this, I do want to get it in. Can you sort out the various style/linter complaints please, and then I think this is ready given it passes some manual testing 🙏

Thank you. There is no hurry 🙂

Signed-off-by: Elias <[email protected]>

calmh · 2025-10-23T20:47:40Z

Actual Windows users who want this, can we have some testing? 🙏

Shablone mentioned this pull request Sep 1, 2025

feat: prevent conhost from pop-up on Windows #10334

Closed

Shablone changed the title ~~Dynamic Console Allocation for Windows~~ feat: Dynamic Console Allocation for Windows Sep 1, 2025

github-actions bot added the enhancement New features or improvements of some kind, as opposed to a problem (bug) label Sep 1, 2025

Shablone force-pushed the main branch 3 times, most recently from 78cad68 to c2552bf Compare September 1, 2025 21:57

rasa reviewed Sep 2, 2025

View reviewed changes

lib/osutil/console_windows.go Show resolved Hide resolved

rasa reviewed Sep 2, 2025

View reviewed changes

calmh reviewed Sep 2, 2025

View reviewed changes

tomasz1986 changed the title ~~feat: Dynamic Console Allocation for Windows~~ feat(build, syncthing): dynamic console allocation for Windows Sep 2, 2025

Shablone force-pushed the main branch 2 times, most recently from 8357fc0 to 79e5eb0 Compare September 3, 2025 17:48

Shablone requested review from calmh and rasa September 3, 2025 19:34

calmh reviewed Sep 15, 2025

View reviewed changes

Shablone marked this pull request as draft September 16, 2025 16:22

Elias added 3 commits September 16, 2025 18:29

feat: use a gui build by default and dynamically attach to console

094b8f5

Signed-off-by: Elias <[email protected]>

fix: build param order

3ebef5e

Signed-off-by: Elias <[email protected]>

fix: add copyright

2252e58

Signed-off-by: Elias <[email protected]>

Elias added 4 commits September 28, 2025 22:21

refactor: improve comments

2cdcdbb

Signed-off-by: Elias <[email protected]>

refactor: remove console initialization from helpHandler

9d2019f

Signed-off-by: Elias <[email protected]>

refactor: replace NoConsole2 with Serve.HideConsole

8a188ab

Signed-off-by: Elias <[email protected]>

fix: remove ssh check

f147a12

Signed-off-by: Elias <[email protected]>

Shablone force-pushed the main branch from fc03903 to 228a270 Compare September 28, 2025 20:21

Merge branch 'upstream-main'

4e247b4

Shablone force-pushed the main branch from a50cc78 to 4e247b4 Compare September 28, 2025 20:24

Elias added 2 commits September 28, 2025 22:42

refactor: replace old hide with new dyncamic allowcation

765dd91

Signed-off-by: Elias <[email protected]>

Merge branch 'dynamic-console-allocation'

3671f50

Shablone marked this pull request as ready for review September 28, 2025 20:44

Shablone requested a review from calmh September 28, 2025 20:57

syncthing deleted a comment from calmh Sep 29, 2025

Merge remote-tracking branch 'upstream/main'

62a3a8c

calmh reviewed Oct 1, 2025

View reviewed changes

Elias and others added 4 commits October 2, 2025 16:04

refactor: simplify openURL function by removing fallback to cmd.exe

765de30

Signed-off-by: Elias <[email protected]>

refactor: simplify openURL function

fca85f0

Signed-off-by: Elias <[email protected]>

Merge branch 'dynamic-console-allocation'

ac27972

Merge branch 'main' into main

60ce0f9

calmh reviewed Oct 21, 2025

View reviewed changes

Elias added 4 commits October 21, 2025 20:40

chore: lint

a8b34d3

Signed-off-by: Elias <[email protected]>

Merge branch 'dynamic-console-allocation'

6a33e0e

fix: simplify consoleAttached

562b043

Signed-off-by: Elias <[email protected]>

Merge branch 'dynamic-console-allocation'

71760ee

Elias added 2 commits October 21, 2025 22:21

chore: fix lint

8f6eb85

Signed-off-by: Elias <[email protected]>

Merge branch 'dynamic-console-allocation'

f984b01

Merge remote-tracking branch 'upstream/main'

8a26722

Uh oh!

Conversation

Shablone commented Sep 1, 2025

Dynamic Console Allocation for Windows

Purpose

Solution

Testing

Implementation

Authorship

Uh oh!

rafaeloledo commented Sep 1, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

rasa commented Sep 2, 2025

Uh oh!

calmh left a comment • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Shablone commented Sep 2, 2025

Uh oh!

calmh commented Sep 2, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

calmh commented Sep 2, 2025

Uh oh!

Shablone commented Sep 2, 2025

Uh oh!

Shablone commented Sep 15, 2025

Uh oh!

tomasz1986 commented Sep 15, 2025

Uh oh!

calmh left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Shablone commented Sep 28, 2025

Uh oh!

Shablone commented Sep 28, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

calmh left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Shablone commented Oct 21, 2025

Uh oh!

calmh commented Oct 23, 2025

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

calmh left a comment •

edited

Loading

calmh commented Sep 2, 2025 •

edited

Loading

Shablone commented Sep 28, 2025 •

edited

Loading