4mo ago

I got to avoid memory management for quite some time

Finally I have a valid reason to learn about memory management. It was also hella weird when encountering it.

65 comments

Unused memory is wasted memory
- Cloud providers LOVE you with this one quick trick!
  
  Also goes for mobile. You use more memory and apps get killed.
- and with a good enough leak, the amount of unused memory will become negative!

Not freeing your memory at all is a memory management strategy. I think some LaTeX compilers use it as well as surprisingly many Java applications.
- .net
  Anything I run in C# or similar seems to allocate 512GB of virtual address space and then just populates what it actually uses.
- That's the funny thing. I had a (yet) very basic Programm and did not care at all about memory management. When I did some testing I realised, that for some reason when I printed string 1 I also got characters from string 2.
  
  That sounds like it could be memory corruption. That should not happen because every string should be separated by a null terminator.
  
  Sounds interesting, want to share a minimal example?
- This non-sarcastically. The operating system is better at cleaning up memory than you, and it's completely pointless to free all your allocations if you're about to exit the program. For certain workloads, it can lead to cleaner, less buggy code to not free anything.
  It's important to know the difference between a "memory leak" and unfreed memory. A leak refers to memory that cannot be freed because you lost track of the address to it. Leaks are only really a problem if the amount of leaked memory is unbounded or huge. Every scenario is different.
  Of course, that's not an excuse to be sloppy with memory management. You should only ever fail to free memory intentionally.
  
  Absolutely. I once wrote a server for a factory machine that spawned child processes to work each job item. Intentionally we did not free any memory in the child process because it serves only one request and then exits anyway. It’s much more efficient to have the OS just clean up everything and provides strong guarantees that nothing can be left behind accidentally for a system where up time was money. Any code to manage memory was pointless line noise and extra developer effort.
  In fact I think in the linker we specifically replaced free with a function that does nothing.
- Upvoted. This is something I learned rather recently. Sometimes it's more performant to slowly leak than it would be to free properly. Then take x amount of time to restart every n amount of time.
  
  A middle ground is a memory pool or an object pool where you reuse the memory rather than free it. Instead, you free it all in one operation when that phase of your application is complete. I’ve seen this done for particle systems to reduce overhead.
- Yeah, you can use the Epsilon garbage collector in Java for a no-op garbage collection strategy.
  For short-lived programs that do not risk hitting any memory constraints, it makes a lot of sense - zero time wasted on cleanup during execution, then you just do it all at the end when killing the program, which you can do in constant time since you don't need to reason about what should remain or not.

Back when I was a kid and was learning C, I used to wonder why people considered pointers hard.
My usage of pointers was like:
C

void func (int * arg1) { // do sth with arg1 } int main () { int x; func (&x); return 0; }
I didn't know stuff like malloc and never felt the need in any of the program logic for the little thingies I made.
Pointers are not hard. Memory management makes it hard.
- C makes them unnecessarily confusing in my opinion. In Forth they're as simple as can be compared to C.

You haven't lived until you've produced a memory leak in JavaScript.

RAII.
Can’t leak what never leaves the stack frame.
- Isn’t this for C++?
  
  Classes are just pretentious structs.

Congratulations! Now you can get a job at Fortinet.
(Fortinet is a network security vendor...think firewalls, HLBs, etc. They get an ungodly amount of memory leak bugs, or at least far more than you would expect from an enterprise firewall)
- Get a job playing Fortnite, got it
  (Insert image of Kronk here)

Valgrind to the rescue

And then OP used valgrind
- I did not knew this existed, so thanks for the tip.
  
  have fun (ノಠ益ಠ)ノ彡┻━┻

is this some genX meme that I'm too millennial to understand?
- No. I am just learning C and was curious how long it would take to get my first memory leak.
  
  I think the confusion comes from this not exactly being a positive thing. It reads almost like a new driver saying, "Thank God I finally got my first speeding ticket!"
- Learn some C you whippersnapper! You ain't gonna become a proper programmer unless you understand your basic low level concepts well!
  The youth nowadays, always hiding behind abstractions of abstractions that 90% of the time are just C wrappers anyway /j
  (written by an early 20s PHP dev LOL. Although I do plan on learning C quite a bit before I move to C++ and ultimately Rust)
  
  You're not a "real" programmer unless you started with FORTRAN :p

It'll be fun when you get to funny errors because you used freed memory.
When I was learning about linked lists and decided to use them in a project, I "removed" items by making the previous item's next point to this item's next, except I misplaced a call to free before using the fields, and it somehow still worked most of the time on debug builds, but on optimized builds it would cause a segmentation fault 100% of the time.

Cruft can be a hard thing to debug. Mainly when you're not used to memory issues and haven't learned all the best practices.
There's also zig if you want to play with memory. You'll know a lot about allocation, that's for sure.

I've used C++20 on embedded devices and the generated code was simpler than the C version. Why do you still use C?
- I want to learn rust and got the recommendation to learn C first.
  
  C is a 100% valid language to spend your time on.
  
  That's a nice recommendation.
  For a beginner without experience in using libraries, the additional requirements in Rust would feel unnecessary and frustrating.
  If you take up Rust after learning programming using C (which won't require all that extra stuff and let you learn the basics easily), that would make it easier for you to appreciate the results of the extra work it makes you do.
  
  Probably a good idea. I decided to learn Rust after using Python for a couple years. I took a semester of C++ but barely remember anything. Maybe I should write a project in C and rewrite later in Rust. I personally only learn when I get inspiration to make a program, which means I learn on the spot. I don't think it is the best way to do things (if I knew the language better I may make better decisions), but it is the only way I can motivate myself to learn.
  
  C is useless nowadays (and has been for at least 20 years). Either learn Rust or C++.

65 comments