The amount of people nitpicking about the brand of pseudocode or arguing the question is tricky reminds me of some coworkers, and not the good kind.
If you belong to the above category, try to learn some new programming language / read about some algorithm descriptions (not implementation) and go out take some sun. The question is super intuitive if you’re not stuck to a single paradigm or language.
So I teach coding to idiots. Confusing or poorly defined abstractions in pseudocode are bad. If you want people to infer useful information from pseudocode, and learn good practices from it, you need to treat it as if there a real underlying class structure written with good practices, or even better, make it comply to some actual language which does that. If you want to imply that this is a member of string, something like string.len_chars is way better imo because it captures the idea of a string being an array<char>. Then the next question can be about string.len_bytes (watch the wheels turn!). That naturally transitions nicely into object oriented paradigms of object containers/storage being at once a templated abstraction with a stride and depth, and also a physical thing in memory.
It makes more sense if you think of const as “read-only”. Volatile just means the compiler can’t make the assumption that the compiler is the only thing that can modify the variable. A const volatile variable can return different results when read different times.
I thought of it more in terms of changing constants (by casting the const away). AFAIK when it’s not volatile, the compiler can place it into read-only data segment or make it a part of some other data, etc. So, technically, changing a const volatile would be less of a UB compared to changing a regular const (?)
const volatile is used a lot when doing HW programming. Const will prevent your code from editing it and volatile prevents the compiler from making assumptions. For example reading from a read only MMIO region. Hardware might change the value hence volatile but you can’t because it’s read only so marking it as const allows the compiler to catch it instead of allowing you to try and fail.
I was thinking about telling them how in embedded systems it’s a good practice to allocate the memory by hand, having in mind the backlog, but yours will come first
AFAIK when it’s not volatile, the compiler can place it into read-only data segment
True, but preventing that is merely a side effect of the volatile qualifier when applied to any random variable. The reason for volatile’s existence is that some memory is changed by the underlying hardware, or by an external process, or by the act of accessing it.
The qualifier was a necessary addition to C in order to support such cases, which you might not encounter if you mainly deal with application code, but you’ll see quite a bit in domains like hardware drivers and embedded systems.
A const volatile variable is simply one of these that doesn’t accept explicit writes. A sensor output, for example.
I’ve never really thought about this before, but const volatile value types don’t really make sense, do they? const volatilepointers make sense, since const pointers can point to non-const values, but constvalues are typically placed in read-only memory, in which case the volatile is kind of meaningless, no?
Maybe there’s a signal handler or some other outside force that knows where that variable lives on the stack (maybe through DWARF) and can pause your program to modify it asynchronously. Very niche. More practical is purely to inhibit certain compiler optimizations.
That seems like a better fit for an intrinsic, doesn’t it? If it truly is a register, then referencing it through a (presumably global) variable doesn’t semantically align with its location, and if it’s a special memory location, then it should obviously be referenced through a pointer.
I’ve used it in the past when having flash memory blocks that could change but you need the compiler to put them into flash memory and not RAM. It’s mainly to get the compiler to stop assuming that it can optimize using the default value.
Around 2 years ago, I got an email from a products team asking me for urgent help extending a program in time to make a sale.
I looked over the program and wrote back sonething along the lines of “this program was written almost a decade ago by an unsupervisered highschool intern. Why TF are we still using it?”.
Of course, I ended up helping them, because that highschool intern was me, and I ended up helping because no one else could figure out what highschool me was thinking.
I sometimes wonder if the spaghetti i wrote when i was still learning to program (on my own, in the corner of the room, ignored by all the “real” devs) is still used by the team i wrote it for.
Idk to me it screams “solve this puzzle and win a free wrench” /s
I like the creativity of it, and it does solve the problem in a way that’s user-safe. I thought of removing the knob because that’s what I do with my barbecue as I store items on the grill when not in use. Remove knobs, put on grill, close barbecue, cover.
A lot of people won’t touch electrical, and the problem with modifying the wiring is you need to be able to clearly document or show what was changed in case it needs to be reversed later.
This is ugly, but it’s immediately obvious how to reverse it to anyone who looks at it. And that pipe wrench probably wasn’t being used anymore anyways. I doubt they tapped the holes, those are probably just self-tap screws that both drilled the hole and cut the thread as they screwed in. No one will call this an elegant solution, but if it works it works.
If you’ve ever worked in maintenance, active production, etc, you’ll be lucky to even have schematics. And trust me, there are a lot of hacks of people fucking with controls for 30+ years straight that soooo much of it is full of “fixes” like this, whether it’s something pushing a button in, or pieces of metal instead of fuses, or wires jumping over what’s “in the way” like whole safety systems and e-stops, contactors forced to run, etc etc etc.
This is sometimes practical, too. For example, hooking and extending functions in compiled code that will never be updated by the original author, while preserving the original executable/library files.
Extension functions are not the same at all. Extension functions are syntactic sugar. For example if you have an extension function like
<span style="color:#323232;">public static class ObjectExtension
</span><span style="color:#323232;">{
</span><span style="color:#323232;"> public static void DoSomething(this object input) { }
</span><span style="color:#323232;">}
</span>
You can call that function on an object by doing object.DoSomething() - Yes. But underneath it’s the same as doing ObjectExtension.DoSomething(object)
That function does not actually become part of the object, and you can’t use it to override existing functions
A closer example of how to do something similar in a memory safe language would be - in C# - using something like Castle DynamicProxy - where through a lot of black magic - you can create a DynamicProxy and fool the CLR into thinking it’s talking to an object, while it’s actually talking to a DynamicProxy instead. And so then you can actually intercept invocations to existing methods and overrule them
Generally overruling existing functions at runtime is not that easy
I thought you were talking about keeping an unmaintained library intact but building onto it.
I thought C was a really dangerous way to use that syntactic sugar pattern. Actual manipulation of the bytecode to maintain and extend a compiled binary is wild
This is sometimes practical, too. For example, hooking and extending functions in compiled code that will never be updated by the original author, while preserving the original executable/library files.
Your original comment made it seem more like extensions - extend and preserve. That’s the misunderstanding.
When I said it’s wild to manipulate bytecode I means “wow that’s a terrifying practice, I would hate to check that PR”
Fair enough. What threw me is that you said “bytecode”, which is generally not used when referring to hardware machine instructions. My original comment is about patching the in-memory image of a running program or library, replacing machine instructions in order to intercept certain calls and extend their behavior.
I thought my phrase “compiled code” would convey this, but I guess nowadays bytecode-compiled languages are so common that some people assume that instead.
Yeah and part of this is that the domain I’ve been working in for years now is very far from machine code, and I’m probably overly lax with my language here.
The result of being in very corporate app dev - I’m usually talking in much higher level abstractions. My bad on conflating bytecode and machine code
Sometimes what I’d like to be able to do is treat part of an app as a core and the rest like user provided scripts, but written and evaluated in the host language and not running an embedded scripting language like lua with all the extra burden.
E.g. you have an image editor and you want the user to be able to write native functions to process the image. Or you have a game engine and you want to inject new game code from the user without the engine being a compiler or the game logic being bundled scripts.
And then you can load plugin classes from all the dlls with dependency injection, and execute them though something like this:
<span style="color:#323232;">public class ImageEditor(IEnumerable<IImageEditorPlugin> plugins)
</span><span style="color:#323232;">{
</span><span style="color:#323232;"> public void EditImage(int[,] imageData)
</span><span style="color:#323232;"> {
</span><span style="color:#323232;"> foreach (var imageEditorPlugin in plugins)
</span><span style="color:#323232;"> {
</span><span style="color:#323232;"> imageEditorPlugin.BeforeImageEdit(imageData);
</span><span style="color:#323232;"> // Do internal image edit function
</span><span style="color:#323232;"> imageEditorPlugin.AfterImageEdit(imageData);
</span><span style="color:#323232;"> }
</span><span style="color:#323232;"> }
</span><span style="color:#323232;">}
</span>
This is a very simple example obviously, normally you’d send more meta-data to the plugins, or have multiple different interfaces depending on the kinda plugin it is, or have some methods to ask plugins when they’re suitable to be used. But this way a user can provide compiled versions of their plugins (in the same language as the core application) - instead of having to provide something like lua scripts
Agreed. It’s a very adult approach. C hands you a running chainsaw and whatever happens after that is your responsibility. It is also your responsibility to decide when it’s not the right time to use C.
C is dangerous like your uncle who drinks and smokes. Y’wanna make a weedwhacker-powered skateboard? Bitchin’! Nail that fucker on there good, she’ll be right. Get a bunch of C folks together and they’ll avoid all the stupid easy ways to kill somebody, in service to building something properly dangerous. They’ll raise the stakes from “accident” to “disaster.” Whether or not it works, it’s gonna blow people away.
C++ is dangerous like a quiet librarian who knows exactly which forbidden tomes you’re looking for. He and his… associates… will gladly share all the dark magic you know how to ask about. They’ll assure you, oh no no no, the power cosmic would never pull someone inside-out, without sufficient warning. They don’t question why a loving god would allow the powers you crave. They will show you which runes to carve, and then, they will hand you the knife.
Rust is like a paranoid overprotective guardian. A “mom friend”, of sorts. Always the designated driver of the group, keeps you from staying up too late, stops you from eating things that might be choking hazards without proper precaution, and so on and so forth. You’ll never meet a person more concerned with your health and safety – until, that is, you say the magic word “unsafe”. Suddenly the alter ego that their hypnotist implanted gets activated, and their entire demeanor changes on a dime. BMX biking? Bungee jumping? Inline assembly? Sounds like a great idea! Let’s go, man! Rules are for NERDS! Then the minute the unsafe block ends, they’re back to normal, fully cognizant of the adventure they just went on and thinking absolutely nothing of it. “Whitewater rafting with you guys was really fun, especially the part where Jason jumped into the water and I went after him! I’d best go get the first aid kit, though – that scrape he got when he did that looks like it might get infected. I know he said it didn’t hurt, but better safe than sorry!”
They kinda scare you when they’re like that, if you’re honest.
This is actually how you should declare something that you will never change, but something might change externally, like an input pin or status register.
Writing to it might do something completely different or just crash, but you also don’t want the compiler getting creative with reads; You don’t want the compiler optimizing out a check for a button press because the “constant” value is never changed.
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