Nah, it was down to my lack of knowledge. Don't worry about it.

You learn something new every day. :)

This seems to be a permanent issue today, at least for me - 3 out of 3 posting attempts appeared to have failed, yet my posts showed just fine upon refreshing the threads.

That's bad news, especially when you see how good the forum software is in preserving code snippets in posts.

I seriously doubt GOG is willing to balloon up their CPU budget doing a full sanitization pass on uploaded images.

I've attached a test file to see whether it's a simple header check.

EDIT: Yep. Just a header check. cat im_a_zip.gif content.zip > test_zip.gif gets past it and I can extract the test file from the re-downloaded image.

(The Windows equivalent would be type im_a_zip.gif content.zip > test_zip.gif)

EXPLANATION: Archives like .zip and [/i].rar[/i] are designed to still be extractable once concatenated onto the end of other files, because that's how self-extractors are made.

(They just concatenate an EXE stub and a Zip/Rar file together to get the final EXE, and the stub knows to examine "itself" to find the archive. Any competent extraction tool (eg. the Linux "unzip" command) will retain that capability so it can unpack self-extractors without running them... though some (eg. the Linux "file-roller" GUI) may be too quick to dismiss unrecognized extensions and only actually try said fallback if the file extension is .exe.)

Of course you always will be able to embed information in a file and make it look like an image (even for more thorough tests). But for an average user it may get harder to extract that information.

Because Zip support is built into every major OS, concatenating a Zip onto a valid image preserves the existing "save with a non-default extension and double-click" workflow.

Worst case scenario, the header detection overrules the extension and the recipient has to manually choose to open it as a Zip file.

...and, though I haven't tested it for universal applicability, the self-synchronizing, block-structured nature of RAR and 7-Zip archives seems to allow it to be embedded in the middle of another kind of file, which would allow it to be stored in a PNG metadata chunk. (Which would allow it pass very strict validity checks while still being compatible with "rename and double-click".)

I know. But seeing how often people already fail to rename an attached text file from *.gif to *.txt to "see" the content on Windows... ;)

If you find yourself often on Windows, but wish you had access to UNIX utilities, it might be worth your while installing Cygwin or WSL (WSL is that "Ubuntu on Windows" thing you might have heard about).

You can also use the xxd command to convert a binary file into a hexdump, upload it to a gist, and then just use xxd -r to reconstruct the original file.

There's also xxd -i, which allows you to convert a binary file into a C variable, which you can then include into a C or C++ application. (Rust has a different method of accomplishing the same task; namely the include_bytes! macro.)

Thanks for the effort, but I'm well aware of Cygwin, WSL, as well as GnuWin32, should a few specific binaries be desired which don't rely on a whole Wine-like translation environment.

I just haven't used Windows in any significant way since I got fed up with XP and switched to MandrakeLinux 10.0 mid-way through Dungeon Siege back around 2003. (And I'd never even consider running anything newer than Windows 7 without airgapping it so WSL is out.)

...though, as a rising hobby, I did recently build a couple of nostalgia PCs on their own quarantined little LAN to which I plan to use to experiment with Windows 3.1 programming and Free Pascal. (Two notable holes in my youthful hobby programming experience.)

I also found a great deal on the Microsoft Windows Resource Kit for Operating System Version 3.1, so I've decided to put together a tool for maximally automated/unattended setup of Windows 3.1 inside DOSBox. (Because it's so darn fragile.)

...which reminds me. If I can ever remember when I have a moment, just for kicks, I want to see how much I can reconfigure one of my old copies of Windows 98SE to look and act like Windows 3.1 using things like the "use Program Manager as the desktop shell" facility Microsoft retained all the way up to Windows XP SP1.

(Sorry for going off on a bit of a tangent there. I just can't bring myself to delete it.)

That would require people to have a copy of xxd.

My solution is compatible with GitHub's browser preview for things like images and geodata, and produces ready-to-use files if it has to fall back to the "Can't preview this. Click to download." message.

That said, thank you for mentioning xxd -i. I didn't know about that and it should be useful when I'm playing around with OpenWatcom C/C++. :)

On my phone (Android, Google Chrome) the chat stopped working. When I try to reach it, I always get redirected to the homepage instead. On my desktop PC (Windows, Firefox 56.0.2) it still works fine.

I had Stronghold HD on my wishlist, and got the Stronghold HD+A.D. 2044 freebie on Oct 24, 2017. Yet the game's still on my wishlist marked as "Owned".

Has anyone else experienced anything similar (lately)?

The email topic GOG sent to me for the MDK key is "Вам подарок!".
I do not think it is a suitable topic since my language setting is English.

I had the same thing with The Witcher 3. Someone gifted me the expansion pass, but Blood and Wine remained on my wishlist and was marked as owned.

I'm sure I had that with a game before too... can't remember which but it did clear off the wishlist eventually...