[bee_rider]

What even is a footgun supposed to be? The analogy doesn’t really make sense, in that… I mean the first thing anybody learns about guns is that they are “always loaded” (even when you know they aren’t) and you only point them at things you want shot.

Is a footgun a gun that only aims at feet? Because that seems like a dumb thing to invent in the first place. Or is it a gun that happens a to be aiming at feet? That seems like something that could only exist by user error.

I think “enough rope to hang yourself” is a more accurate description of almost every programming languages, since rope is at least intended to be useful (although it is a bit more morbid of an analogy).

[rmwaite]

Imagine that you had a gun and one of the features of the gun was that if you had sunglasses on and something in your left pocket, holstering the gun would cause it to immediately fire. You could argue that the gun shouldn’t behave this way, but it’s also possible that others are dependent on this behavior and you can’t remove it.

This is a footgun - the way to avoid the holster firing is to simply not wear sunglasses, or keep something in your left pocket, and then it would never fire. But the problem is that both of those things are extremely common (for good reason). It’s a poorly thought out feature because it has severe consequences (potentially shooting your foot) for extremely common situations (wearing sunglasses and using your left pocket).

[bee_rider]

I basically don’t agree that anybody could depend on this holstering-causes-it-to-fire behavior. Or at least, their use-case requires design compromises that are so unthinkably ridiculous as to make the gun they want something that no reasonable person without that use-case would use.

It is possible that the entire field of programming is full of ridiculous people. But it seems more likely that C++ is like a gun with no safety, or something along those lines.

[AnthonyMouse]

A lot of the footguns come from compiler authors wanting to make things UB because it allows them to perform certain optimizations, but then you end up with a lot of things that are formally UB even though in practice they usually do the intuitively expected thing. But then, because the widely done thing is actually UB, the compiler is allowed to do something counterintuitive which causes your program to blow up.

An obvious example is omitting NULL pointer checks. Passing a NULL pointer to certain system library functions is UB even if it would ordinarily be expected to be reasonable, e.g. memset(NULL, 0, 0), so some compilers will see that you passed a pointer to memset, and passing a NULL pointer to memset is UB, therefore it can omit a subsequent NULL pointer check guarding a call to something else when the something else isn't going to behave reasonably given a NULL pointer.

This is an insane footgun, but it also allows the compiler to omit a runtime NULL pointer check, which makes the program faster, so people who care most about performance lobby to keep it.

[samatman]

Just to carry onwards with the use/mention distinction we're aggressively erasing here, you seem to question whether actual, real-life footguns exist.

They do! Here's a reference. https://en.wikipedia.org/wiki/Slamfire

Another common way to shoot yourself in the foot is a gun which will go off if you drop it. An example of a gun where early models were especially susceptible is the Lanchester: https://en.wikipedia.org/wiki/Lanchester_submachine_gun

[kelnos]

> I basically don’t agree that anybody could depend on this holstering-causes-it-to-fire behavior.

It's an idiom. It's not supposed to be entirely logically consistent. It means what it means because people have decided that it means what it means. Your objections aren't really relevant.

"Footgun" is I think a fairly recent addition to the English lexicon, but it's based on the centuries-old "to shoot yourself in the foot". It seems silly to argue with centuries of English idiomatic usage; no one, by definition, is going to win an argument against that.

[wvenable]

Yeah I don't think that's a good analogy. Instead, you have guns that don't let you point at your feet. So you can never shoot yourself there. However, if you ever need to shoot straight down for a legitimate reason, you're out of luck. In C++, you can shoot everywhere without restrictions and sometimes that means shooting yourself in the foot or the head.

[kelnos]

"Footgun" comes from the English idiom "to shoot yourself in the foot", which means "to act against your own interests" (usually accidentally). (Consider similar idioms, like "to dig your own grave".)

I think you're being a bit too literal. It's not an analogy at all, and this has nothing to do with firearms best practices. If we were to define a footgun as "a gun that is only capable of shooting you in the foot" (or perhaps more broadly usefully, "a gun that in theory can be useful, but it is nearly impossibly difficult to make it do anything other than shoot you in the foot"), then the entire point of using the term is to describe something that has no useful, logical purpose, and is unsafe to use, even as designed.

Being "given enough rope to hang yourself" is indeed another good idiom to use for things like this, but the implication is different, I think: when you're given enough rope to hang yourself, the outcome is still very much in your hands. You can intentionally or unintentionally use that rope to hang yourself, or you can be reasonably expected to use that rope in another way that would turn out to be safe or useful.

"Footgun", by contrast, is used to describe something that has no (or negligible) safe uses. Maybe the original intent behind the design of what's being described that way was to have safe uses, but ultimately those safe uses never really panned out, or were so dwarfed by the unsafe uses that the safe use isn't worth the thing existing in the first place. But, unfortunately, there are some people -- maybe only 0.01% of people -- who are able use it safely, and critically depend on that safe use, so we can't completely destroy all these footguns and save everyone else from the error of their ways. And unfortunately most everyone else sees these 0.01% of uses, and believes they are so useful, so efficient, so brilliant, they want to try it too... but in their hubris they end up shooting themselves in the foot, like most others before them.

[samatman]

I've long been partial to this formulation:

> 1972 - Dennis Ritchie invents a powerful gun that shoots both forward and backward simultaneously. Not satisfied with the number of deaths and permanent maimings from that invention he invents C and Unix.

Some of us learn to lean to the side right before pulling the trigger...

http://james-iry.blogspot.com/2009/05/brief-incomplete-and-m...

[sqeaky]

At this point a footgun can stand alone in this industry as a term with its own meaning outside of analogy.

It is any trap in something technical that is likely to cause problems from perceived normal use.

Compare to related terms: "Pit of failure", "Turing tarpit", and "Pit of success".