# Rust lang memory management

**URL:** <https://discourse.ats-lang.org/t/rust-lang-memory-management/599>\
**Category:** Google Group\
**Created:** [October 1, 2014, 4:20pm UTC](https://discourse.ats-lang.org/t/rust-lang-memory-management/599 "2014-10-01T16:20:34Z")\
**Posts on this page:** 9\
**Page:** 3

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**Author:** ![H\_Zhang](https://avatars.discourse-cdn.com/v4/letter/h/b77776/32.png) [@H\_Zhang](https://discourse.ats-lang.org/u/H_Zhang)\
**Post date:** [October 2, 2014, 1:50am UTC](https://discourse.ats-lang.org/t/rust-lang-memory-management/599/41 "2014-10-02T01:50:49Z")

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GC is not bad per se. We don’t write code in isolation. I interact with  
GC’ed languages all day long, but sometimes I need to drop down to a lower  
level to write extensions. You can’t just put GC in a library willy nilly.On Wed, Oct 1, 2014 at 4:36 PM, Raoul Duke [rao...@gmail.com](mailto:rao...@gmail.com) wrote:

> On Wed, Oct 1, 2014 at 3:57 PM, Haitao Zhang [zht...@gmail.com](mailto:zht...@gmail.com) wrote:
> 
> > That requires GC at some stage
> 
> why is GC so bad? 🙂
> 
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> .

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**Author:** ![H\_Zhang](https://avatars.discourse-cdn.com/v4/letter/h/b77776/32.png) [@H\_Zhang](https://discourse.ats-lang.org/u/H_Zhang)\
**Post date:** [October 1, 2014, 7:01pm UTC](https://discourse.ats-lang.org/t/rust-lang-memory-management/599/42 "2014-10-01T19:01:42Z")

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Rust is Apache/MIT licensed so that whatever they do should be okay to  
borrow in ATS as well?

The way I think about the language mismatch problem, if we take data  
structures as the central of focus of programming, is that managed  
languages don’t let you control every detail of the data structure that is  
most important to you, while c/c++ forces you to manage every little detail  
that is unimportant to you. For the data structure that carries the whole  
program state I want to be very careful about everything, but in any given  
function I am only working on a small part of it I want to be able to use  
abstract (not just primitive) temporary or not so temporary smallish  
structures without having to manually manage all the life cycles. I don’t  
know if Rust is It but I do think it is an important gap to address.On Wednesday, October 1, 2014 10:35:18 AM UTC-7, gmhwxi wrote:

> Interesting.
> 
> My guess is that some kind of (sophisticated) flow analysis is involved.
> 
> > > Is everything on stack?
> 
> Putting everything on stack would make it so difficult to do  
> general-purpose programming  
> even if it is still possible.
> 
> > > Why can’t ATS do something similar?
> 
> You mean to rely on flow analysis (instead of linear types) for memory  
> management?
> 
> Well, this has to do with my training. The lessons I learned from  
> automated theorem-proving  
> made me constantly try to avert complex algorithms of heavy heuristic  
> nature.
> 
> On Wednesday, October 1, 2014 12:20:34 PM UTC-4, H Zhang wrote:
> 
> > Rust is able to do support ADT and pattern matching without requiring the  
> > use of GC. Does anyone know how that is achieved? Is everything on stack?  
> > Why can’t ATS do something similar?
> > 
> > Haitao

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<div class="post-metadata">

**Author:** ![Raoul\_Duke](https://avatars.discourse-cdn.com/v4/letter/r/bbe5ce/32.png) [@Raoul\_Duke](https://discourse.ats-lang.org/u/Raoul_Duke)\
**Post date:** [October 1, 2014, 5:54pm UTC](https://discourse.ats-lang.org/t/rust-lang-memory-management/599/43 "2014-10-01T17:54:53Z")

</div>

> However, the values to be matched against are usually compound values  
> that need to be created at run-time. I guess Haitao’s question is about  
> where  
> such compound values are stored and how they are freed.

i still don’t get it. i can have (things approximating at least) ADTs  
in C/++/Obj-C, can i not?

(note: i’m not arguing for non-gc, i just do not yet understand the  
issue here, it all seems confused and conflated and confabulated to  
me.)

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**Author:** ![gmhwxi](https://avatars.discourse-cdn.com/v4/letter/g/67e7ee/32.png) [@gmhwxi](https://discourse.ats-lang.org/u/gmhwxi)\
**Post date:** [October 1, 2014, 8:05pm UTC](https://discourse.ats-lang.org/t/rust-lang-memory-management/599/44 "2014-10-01T20:05:52Z")

</div>

The typechecker of ATS will enforce type-correctness,  
which will get rid of a lot of stupid bugs.On Wednesday, October 1, 2014 4:00:57 PM UTC-4, Raoul Duke wrote:

> it isn’t the burden of finger typing on keyboards.
> 
> it is the burden of stupid bugs crashes etc. later.

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**Author:** ![Shea\_Levy](https://avatars.discourse-cdn.com/v4/letter/s/b38774/32.png) [@Shea\_Levy](https://discourse.ats-lang.org/u/Shea_Levy)\
**Post date:** [October 1, 2014, 10:50pm UTC](https://discourse.ats-lang.org/t/rust-lang-memory-management/599/45 "2014-10-01T22:50:37Z")

</div>

If you want to just do exe\_name := file\_name\_step + “.exe” and not have  
to worry about it, then what’s wrong exactly with using normal ADTs?

~SheaOn Wed, Oct 01, 2014 at 03:41:40PM -0700, H Zhang wrote:

> The problem with letting it dangle now and fix it later that is: 1) I have  
> to remember doing that and also pick up what I was doing before and 2)  
> assuming the tools give meaningful warnings so I can go right to where the  
> issue is the “fix” would still pollute the code and make it harder to read.  
> Really I should be able to say exe\_name := file\_name\_stem + “.exe” and  
> forget about it. I don’t care about the performance here nor memory usage.  
> Just needs it to be safe. But it is a heavy price to pay if I have to use  
> Python to get little niceties like this. If 90% of the cases can be handled  
> automatically I don’t mind handling the cases that can’t be resolved. Then  
> I can reserve the mental energy to use linear types on things that really  
> matter to me performance wise (time and space).
> 
> On Wednesday, October 1, 2014 2:45:06 PM UTC-7, gmhwxi wrote:
> 
> > > > It is the mental distraction that is annoying.
> > 
> > I once tried to juggle 3 oranges (or apples) in front of the students  
> > taking my class  
> > so as to show them how difficult it is. When programming, people tend to  
> > juggle many  
> > concepts mentally, complicating programming unnecessarily.
> > 
> > In ATS, you can always use a non-linear type first and then change it to a  
> > linear one  
> > later. This allows you to focus on what you are doing.
> > 
> > On Wed, Oct 1, 2014 at 4:40 PM, H Zhang \<[zht...@gmail.com](mailto:zht...@gmail.com) \<javascript:\>\> wrote:
> > 
> > > It is the mental distraction that is annoying. E.g. in C for something  
> > > trivial like changing the extension of a filename one needs to allocate a  
> > > string, pass it on and later remember to free it. That is just very  
> > > distracting from the logical flow. Not only that, it is very annoying to  
> > > read codes that are littered with things like that as it interferes with  
> > > following the programmer’s true intention.
> > > 
> > > On Wednesday, October 1, 2014 12:48:40 PM UTC-7, gmhwxi wrote:
> > > 
> > > > > > without having to manually manage all the life cycles
> > > > 
> > > > Your assumption is that this must be very burdensome. But really? One  
> > > > needs to actually  
> > > > do it in order to get a real sense of it.
> > > > 
> > > > Think about a system that you want to implement. If there is something  
> > > > that prevents you from  
> > > > implementing the system, I bet it is unlikely due to the need to  
> > > > manually manage something; it  
> > > > usually happens at a much earlier stage.
> > > > 
> > > > On Wednesday, October 1, 2014 3:01:43 PM UTC-4, H Zhang wrote:
> > > > 
> > > > > Rust is Apache/MIT licensed so that whatever they do should be okay to  
> > > > > borrow in ATS as well?
> > > > > 
> > > > > The way I think about the language mismatch problem, if we take data  
> > > > > structures as the central of focus of programming, is that managed  
> > > > > languages don’t let you control every detail of the data structure that is  
> > > > > most important to you, while c/c++ forces you to manage every little detail  
> > > > > that is unimportant to you. For the data structure that carries the whole  
> > > > > program state I want to be very careful about everything, but in any given  
> > > > > function I am only working on a small part of it I want to be able to use  
> > > > > abstract (not just primitive) temporary or not so temporary smallish  
> > > > > structures without having to manually manage all the life cycles. I don’t  
> > > > > know if Rust is It but I do think it is an important gap to address.
> > > > > 
> > > > > On Wednesday, October 1, 2014 10:35:18 AM UTC-7, gmhwxi wrote:
> > > > > 
> > > > > > Interesting.
> > > > > > 
> > > > > > My guess is that some kind of (sophisticated) flow analysis is  
> > > > > > involved.
> > > > > > 
> > > > > > > > Is everything on stack?
> > > > > > 
> > > > > > Putting everything on stack would make it so difficult to do  
> > > > > > general-purpose programming  
> > > > > > even if it is still possible.
> > > > > > 
> > > > > > > > Why can’t ATS do something similar?
> > > > > > 
> > > > > > You mean to rely on flow analysis (instead of linear types) for memory  
> > > > > > management?
> > > > > > 
> > > > > > Well, this has to do with my training. The lessons I learned from  
> > > > > > automated theorem-proving  
> > > > > > made me constantly try to avert complex algorithms of heavy heuristic  
> > > > > > nature.
> > > > > > 
> > > > > > On Wednesday, October 1, 2014 12:20:34 PM UTC-4, H Zhang wrote:
> > > > > > 
> > > > > > > Rust is able to do support ADT and pattern matching without requiring  
> > > > > > > the use of GC. Does anyone know how that is achieved? Is everything on  
> > > > > > > stack? Why can’t ATS do something similar?
> > > > > > > 
> > > > > > > Haitao
> > > > > > 
> > > > > > –  
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> > > > > > \<javascript:\>.  
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> > > > > > .
> 
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<div class="post-metadata">

**Author:** ![gmhwxi](https://avatars.discourse-cdn.com/v4/letter/g/67e7ee/32.png) [@gmhwxi](https://discourse.ats-lang.org/u/gmhwxi)\
**Post date:** [October 2, 2014, 1:18am UTC](https://discourse.ats-lang.org/t/rust-lang-memory-management/599/46 "2014-10-02T01:18:02Z")

</div>

Yes, you can have different sets of malloc/free pairs as long as you don’t  
use GC.  
If you use GC, then you probably do not want to have different sets of  
malloc/free pairs.On Wednesday, October 1, 2014 7:27:41 PM UTC-4, H Zhang wrote:

> Yes that is what regions analysis does. That is a good “poor man”'s  
> substitute for regions analysis but I think in ATS you can’t really specify  
> multiple mallocs (?). You would have to drop back to C to do that.
> 
> On Wed, Oct 1, 2014 at 4:17 PM, Barry Schwartz \< [chem...@chemoelectric.org](mailto:chem...@chemoelectric.org) \<javascript:\>\> wrote:
> 
> > H Zhang \<[zht...@gmail.com](mailto:zht...@gmail.com) \<javascript:\>\> skribis:
> > 
> > > The problem with letting it dangle now and fix it later that is: 1) I  
> > > have  
> > > to remember doing that and also pick up what I was doing before and 2)  
> > > assuming the tools give meaningful warnings so I can go right to where  
> > > the  
> > > issue is the “fix” would still pollute the code and make it harder to  
> > > read.  
> > > Really I should be able to say exe\_name := file\_name\_stem + “.exe” and  
> > > forget about it. I don’t care about the performance here nor memory  
> > > usage.  
> > > Just needs it to be safe. But it is a heavy price to pay if I have to  
> > > use  
> > > Python to get little niceties like this. If 90% of the cases can be  
> > > handled  
> > > automatically I don’t mind handling the cases that can’t be resolved.  
> > > Then  
> > > I can reserve the mental energy to use linear types on things that  
> > > really  
> > > matter to me performance wise (time and space).
> > 
> > In my working days as a C programmer of slow programs that could eat  
> > up memory freely, I used to use a little ‘reaping allocator’ I  
> > wrote. Not at all complicated. Call it instead of malloc directly, and  
> > use it just like malloc, but the allocated pieces had a link field in  
> > them so you could free them all at once. So I’d start up the allocator  
> > at the beginning of routine and put a ‘reap’ at the end. In between, I  
> > could act somewhat as if I had a garbage collector.
> > 
> > Simple solutions often work fine.
> > 
> > (Python OTOH makes things so complicated that I wouldn’t trust a proof  
> > of correctness of some Python code if it existed, and don’t trust  
> > tests.)
> > 
> > –  
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> > .

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<div class="post-metadata">

**Author:** ![Raoul\_Duke](https://avatars.discourse-cdn.com/v4/letter/r/bbe5ce/32.png) [@Raoul\_Duke](https://discourse.ats-lang.org/u/Raoul_Duke)\
**Post date:** [October 1, 2014, 9:48pm UTC](https://discourse.ats-lang.org/t/rust-lang-memory-management/599/47 "2014-10-01T21:48:52Z")

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> In ATS, you can always use a non-linear type first and then change it to a  
> linear one  
> later. This allows you to focus on what you are doing.

do i get it right that you can start with Boehm first, too? as the  
most easy route to Getting Something Working. and then easily  
(easily?) migrate to statically tracked manual memory management?

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<div class="post-metadata">

**Author:** ![Raoul\_Duke](https://avatars.discourse-cdn.com/v4/letter/r/bbe5ce/32.png) [@Raoul\_Duke](https://discourse.ats-lang.org/u/Raoul_Duke)\
**Post date:** [October 1, 2014, 8:00pm UTC](https://discourse.ats-lang.org/t/rust-lang-memory-management/599/48 "2014-10-01T20:00:36Z")

</div>

it isn’t the burden of finger typing on keyboards.

it is the burden of stupid bugs crashes etc. later.

---

<div class="post-metadata">

**Author:** ![Raoul\_Duke](https://avatars.discourse-cdn.com/v4/letter/r/bbe5ce/32.png) [@Raoul\_Duke](https://discourse.ats-lang.org/u/Raoul_Duke)\
**Post date:** [October 1, 2014, 8:12pm UTC](https://discourse.ats-lang.org/t/rust-lang-memory-management/599/49 "2014-10-01T20:12:53Z")

</div>

> The typechecker of ATS will enforce type-correctness,  
> which will get rid of a lot of stupid bugs.

sure, agreed, i’m all for good typing 🙂 e.g. i assume/hope also  
especially if linears are used to statically find memory problems.

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