Hi When does we use pointer to something in return type

Question

Go

Mehrad

Hi When does we use pointer to something in return type

as signature instead of the type it self ?
func function () *T
Instead
Func function () T

What is the benefit ?

0

13.11.2023

17 ответов

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Mehrad Автор вопроса

Sebastian
T in this case is an copy of an type. Different go...

what about method receivers ? can i always use pointer receiver instead of value receiver ? when should i use value receiver ?

0

13.11.2023

Akshit

Mehrad
what about method receivers ? can i always use poi...

Think of receivers as a first argument to your function. Non-pointer receivers will copy. Now depending on what you want to do — mutate or not, and how big the data structure is, you may prefer one over the other. Although the rule of thumb is, be consistent with your receivers, and when in doubt, use a pointer receiver.

0

13.11.2023

Roman Sharkov

Mehrad
what about method receivers ? can i always use poi...

https://go.dev/tour/methods/8 don 't forget however, that copying small stuff (usually < 64 bytes) is very cheap and pointers usually cause allocation on the heap, which creates garbage that the garbage collector will have to clean up. If you create too much garbage you will unnecessarily slow down your code.

0

13.11.2023

Akshit

Sebastian
T in this case is an copy of an type. Different go...

It depends. maps and slices are passed by reference. In case the T is a slice or a map, you are essentially passing a pointer to a reference.

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13.11.2023

Roman Sharkov

Akshit
It depends. maps and slices are passed by referenc...

sometimes this is necessary if you want to append onto a slice for example

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13.11.2023

Akshit

Roman Sharkov
sometimes this is necessary if you want to append ...

You mean a pointer to a slice? Never seen that.

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13.11.2023

Akshit

Both of them produce the same result, but from what i've seen, returning the new slice is "more idiomatic"

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13.11.2023

Mehrad Автор вопроса

Akshit
You mean a pointer to a slice? Never seen that.

append has a new allocation inside (when resizing) if you dont pass pointer you will get wrong behavior

0

13.11.2023

Thomas

Akshit

Both of them produce the same result, but from wha...

pointer usage is reasonable to me

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13.11.2023

Akshit

Mehrad
append has a new allocation inside (when resizing)...

It's not "wrong behaviour". Its the behaviour you wrote. The computer does what it is being told.

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13.11.2023

Akshit

Thomas
pointer usage is reasonable to me

Its reasonable, and fine to do. But what I'm saying is I have seen more returning the new slice than passing by pointer.

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13.11.2023

Thomas

Akshit
Its reasonable, and fine to do. But what I'm sayin...

ahh yea

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13.11.2023

Mehrad Автор вопроса

Akshit
It's not "wrong behaviour". Its the behaviour you ...

so u should use pointer not get your wrong behavior

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13.11.2023

Akshit

Thomas
ahh yea

Although I'm curious if one is "more optimized" by the compiler than the other.

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13.11.2023

Thomas

Akshit
Although I'm curious if one is "more optimized" by...

The pointer one is likely superior if anything

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13.11.2023

Akshit

Thomas
The pointer one is likely superior if anything

I doubt. Let me dump the SSA.

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13.11.2023

Sebastian · Accepted Answer

Sebastian

T in this case is an copy of an type. Different goroutines can act on it without affecting the others. With pointers they access the same memory and when the wrize to that shared space it can lead to problems. Copies are rather expensive for bigger objects, so sometimes the originals are pooled and only accessed through pointers.

0

13.11.2023

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Hi When does we use pointer to something in return type

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