Ownership semantics are a set of rules that govern the lifetime of allocated resources. Ownership semantics determine when and how allocated resources can be freed, and whether ownership can be shared.
Questions tagged [ownership-semantics]
67 questions
2
votes
1 answer
Do Rust collections have the ability to own the data they store?
Given the following code (which does not compile):
fn main() {
let mut v = vec!();
{
let name = "Bob the Builder".to_string();
v.push(&name);
}
for m in &v{
println!("{}", m);
}
}
I have created a…
Ralph Caraveo
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2
votes
1 answer
Can Rust consume an iterator passed into a function?
I'm trying to implement a simple REPL calculator in Rust and I'm hitting brick walls all over the place.
I'm consuming chars while iterating over a hardcoded string. When I hit a numeric character I want to pass control over to a function that will…
neektza
- 483
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- 11
2
votes
2 answers
How to manage object life time using Boost library smart pointers?
There is a scenario that i need to solve with shared_ptr and weak_ptr smart pointers.
Two threads, thread 1 & 2, are using a shared object called A. Each of the threads have a reference to that object. thread 1 decides to delete object A but at the…
red.clover
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1
vote
1 answer
How do I model a non-owning view on some resource (not itself managed via shared_ptr), if not via raw pointer?
std::unique_ptr is for exclusive ownership.
std::shared_ptr is for shared ownership.
So it looks like a raw pointer is left just the job of being a non-owning pointer, at least in good code.
But if I see a raw pointer somewhere, I actually don't…
Enlico
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1
vote
1 answer
Pass ownership of an object into method of the same object?
I came across come C++ code similar to the following (more or less minimal) example. Please consider the marked method call in the function on the bottom:
#include
static unsigned returnValue = 5;
void setReturnValue(unsigned u) {…
HelpingHand
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- 27
1
vote
1 answer
Sharing arrays between threads in Rust
I'm new to Rust and I'm struggling with some ownership semantics.
The goal is to do some nonsense measurements on multiplying 2 f64 arrays and writing the result in a third array.
In the single-threaded version, a single thread takes care of the…
pveentjer
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1
vote
3 answers
Moving objects can change the order destructors are called. Why isn't that a problem?
In the following example, a mutex is used to protect a file:
#include
#include
#include
std::mutex m;
int main() {
std::unique_ptr> ptr_1 =…
Mark Wallace
- 528
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- 12
1
vote
1 answer
Fire event at changing refcount in PHP
When refcount = 0, the __destruct magic method is called. Is there any way to catch the fact that refcount is decreased or increased, but not zero?
A use-case for such an event is to detect if an object is being shared (refcount > 1) or owned…
Olle Härstedt
- 3,799
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1
vote
1 answer
Immutable Strings and Cloning
I have the mindset keeping my Strings immutable, a single source of truth.
As I take the same mindset into Rust, I find I have to do a lot of cloning.
Since the Strings do not change, all the cloning is unnecessary.
Below there is an example of this…
NebulaFox
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1
vote
1 answer
Movable but non-copyable objects: passing by value vs by reference?
Considering only objects that are movable but non-copyable (e.g., std::thread or std::unique_ptr), I want to transfer the ownership of the resource such an object contains by passing it as an argument to a constructor. I'm comparing two approaches:…
JFMR
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1
vote
2 answers
calling functions which take unique_ptr object
I have a function in which the callback receives an event holding a unique_ptr instace of data. I can retrieve the char* through event.data.get() which should give me the pointer but not ownership allowing the object to freely delete it. Now I have…
Irelia
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1
vote
2 answers
How to organize object ownership for class that lives lesser time than owner of the object?
I have the following situation: there is class of GraphicsContext:
class GraphicsContext {
...
private:
std::unique_ptr m_renderer;
}
And there is a class of application that uses the GraphicsContext:
class Application {
…
Nikolai
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1
vote
1 answer
Swift unowned self leaking when 'owned' by a view being presented
I am experiencing a leak with unowned self under conditions where, to the best of my knowledge, there shouldn't be a leak. Let me show an example, it is a little contrived, so bear with me, I've tried to make the simplest case I could.
Suppose I…
Darumar
- 71
- 9
1
vote
1 answer
Why does the Rust book present assigning a variable to another as copying the top-level structure?
In the section on ownership in The Rust Programming Language, Strings are represented as a structure with 3 fields (with one of the 3 fields being a pointer to the actual byte vector). There is an example:
let s1 = String::from("hello");
let s2 =…
Stefan
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1
vote
1 answer
What is the difference between dereferencing a raw pointer to a String and a raw pointer to an i32?
fn func(s: *mut String, a: *mut i32) -> usize {
println!("{}", unsafe { *s });
println!("{}", unsafe { *a });
unsafe { (*s).len() }
}
fn main() {
let mut s = String::from("hello");
let mut a = 10;
func(&mut s, &mut…
soupybionics
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