# Does std.process.Init.environ\_map allocate memory or not? **URL:** \ **Category:** Explain\ **Tags:** memory-management, standard-library, zig-0-16\ **Created:** [April 27, 2026, 3:56pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202 "2026-04-27T15:56:12Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Ahmad](https://ziggit.dev/user_avatar/ziggit.dev/ahmad/32/10010_2.png) [@Ahmad](https://ziggit.dev/u/Ahmad)\ **Post date:** [April 27, 2026, 3:56pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/1 "2026-04-27T15:56:12Z")
The doc comment for it says “Environment variables, initialized with gpa" so when I used it first time I did the following ```zig const environ_map = init.environ_map; defer environ_map.deinit(); ``` But it failed … ```sh thread 16198 panic: integer overflow Unwind error at address `./development:0x2dc2f6` (unwind info unavailable), remaining frames may be incorrect ???:?:?: 0x3e12ff in multi_array_list.MultiArrayList(array_hash_map.Custom([]const u8,[]const u8,process.Environ.Map.EnvNameHashContext,false).Data).slice (./development) ???:?:?: 0x3e1ff0 in multi_array_list.MultiArrayList(array_hash_map.Custom([]const u8,[]const u8,process.Environ.Map.EnvNameHashContext,false).Data).items__anon_24407 (./development) ???:?:?: 0x3e1f28 in array_hash_map.Custom([]const u8,[]const u8,process.Environ.Map.EnvNameHashContext,false).keys (./development) ???:?:?: 0x3e1df6 in process.Environ.Map.keys (./development) ???:?:?: 0x44761e in process.Environ.Map.deinit (./development) ???:?:?: 0x442e83 in start.posixCallMainAndExit (./development) ???:?:?: 0x441bf1 in start.\_start (./development) zsh: abort ./development ``` I removed the deinit part and it was fine(I also tried making environ\_map mutable). Another thing that added to the confusion is … ```zig const environ = init.minimal.environ; var environ_map = environ.createMap(gpa); defer environ_map.deinit(); ``` So, does it allocate? If so, then how come that it didn’t accept an allocator parameter? If not, then what is the significance of the part of the doc comment that says “initialized with gpa”? ---
**Author:** ![Southporter](https://ziggit.dev/user_avatar/ziggit.dev/southporter/32/2500_2.png) [@Southporter](https://ziggit.dev/u/Southporter)\ **Post date:** [April 27, 2026, 4:04pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/2 "2026-04-27T16:04:12Z")
Hi @Ahmad , welcome to Ziggit! Juicy main does the deinit for you. So the ones passed into main will be initialized with GPA and should handle the deinit as well. For the second example, because you are creating the map, you are in charge of deallocating. That’s why the `deinit` works fine. ---
**Author:** ![Ahmad](https://ziggit.dev/user_avatar/ziggit.dev/ahmad/32/10010_2.png) [@Ahmad](https://ziggit.dev/u/Ahmad)\ **Post date:** [April 27, 2026, 5:00pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/3 "2026-04-27T17:00:02Z")
The source of all this for me is that I didn’t pass an allocator parameter, but if I understand correctly this is the first exception to that rule. ---
**Author:** ![Southporter](https://ziggit.dev/user_avatar/ziggit.dev/southporter/32/2500_2.png) [@Southporter](https://ziggit.dev/u/Southporter)\ **Post date:** [April 27, 2026, 5:35pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/4 "2026-04-27T17:35:35Z")
A general rule of thumb is if you didn’t ever pass an allocator, then you don’t have to call `deinit`. This is a special case of that rule. Juicy main did the allocation, so you don’t have to. The special case is that since juicy main does the deallocation, you don’t have to worry about it, even if you call one of the apis and pass in an allocator. ---
**Author:** ![pachde](https://ziggit.dev/user_avatar/ziggit.dev/pachde/32/2485_2.png) [@pachde](https://ziggit.dev/u/pachde)\ **Post date:** [April 27, 2026, 6:01pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/5 "2026-04-27T18:01:41Z")
‘deinit’ doesn’t always mean deallocation: it can be closing a database handle and similar resource release. ---
**Author:** ![Southporter](https://ziggit.dev/user_avatar/ziggit.dev/southporter/32/2500_2.png) [@Southporter](https://ziggit.dev/u/Southporter)\ **Post date:** [April 27, 2026, 6:29pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/6 "2026-04-27T18:29:05Z")
True. I was talking more about allocation specifically. It’s good to call this out. Generally if you create the resource, you are incharge of calling `deinit` ---
**Author:** ![LucasSantos91](https://ziggit.dev/user_avatar/ziggit.dev/lucassantos91/32/440_2.png) [@LucasSantos91](https://ziggit.dev/u/LucasSantos91)\ **Post date:** [April 27, 2026, 6:32pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/7 "2026-04-27T18:32:18Z")
> [@Southporter](#): > > Juicy main does the deinit for you. So the ones passed into main will be initialized with GPA and should handle the deinit as well. Hidden control flow has crept into zig. ---
**Author:** ![Chaz](https://ziggit.dev/letter_avatar_proxy/v4/letter/c/4491bb/32.png) [@Chaz](https://ziggit.dev/u/Chaz)\ **Post date:** [April 27, 2026, 6:57pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/8 "2026-04-27T18:57:58Z")
> [@LucasSantos91](#): > > Hidden control flow has crept into zig. I’m not sure what you mean here. ---
**Author:** ![pachde](https://ziggit.dev/user_avatar/ziggit.dev/pachde/32/2485_2.png) [@pachde](https://ziggit.dev/u/pachde)\ **Post date:** [April 27, 2026, 8:08pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/9 "2026-04-27T20:08:34Z")
Not if you go read start.zig 😉 ---
**Author:** ![Ahmad](https://ziggit.dev/user_avatar/ziggit.dev/ahmad/32/10010_2.png) [@Ahmad](https://ziggit.dev/u/Ahmad)\ **Post date:** [April 27, 2026, 8:13pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/10 "2026-04-27T20:13:15Z")
Then it will also be true for any programming language if your read the source code and documentation. At this point hidden flow is not but an illusion ---
**Author:** ![DEN0MINAT0R](https://ziggit.dev/letter_avatar_proxy/v4/letter/d/a88e4f/32.png) [@DEN0MINAT0R](https://ziggit.dev/u/DEN0MINAT0R)\ **Post date:** [April 27, 2026, 8:41pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/11 "2026-04-27T20:41:07Z")
I mean… no. Memory allocation is not control flow. Also, this is exactly the same as any other case where someone hands you some memory that you didn’t allocate— if you didn’t allocate it then you shouldn’t be responsible for freeing it. At best this is a hidden dynamic allocation, since you have to know about the different process initialization options to control it, but in no way is this control flow. ---
**Author:** ![LucasSantos91](https://ziggit.dev/user_avatar/ziggit.dev/lucassantos91/32/440_2.png) [@LucasSantos91](https://ziggit.dev/u/LucasSantos91)\ **Post date:** [April 27, 2026, 9:03pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/12 "2026-04-27T21:03:51Z")
OP’s initial code and argument (passing a gpa to the map) seemed very reasonable to me. The reason why it failed was hidden in non-trivial code which was nowhere in his source code or dependencies. That’s hidden control flow, or hidden code, whatever you want to call it. ---
**Author:** ![squeek502](https://ziggit.dev/user_avatar/ziggit.dev/squeek502/32/409_2.png) [@squeek502](https://ziggit.dev/u/squeek502)\ **Post date:** [April 27, 2026, 9:16pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/13 "2026-04-27T21:16:41Z")
Since nobody has linked it, here’s the relevant part of `start.zig`: [https://codeberg.org/ziglang/zig/src/commit/764760df62c63bc2a3d4bd4ec95c000233625834/lib/std/start.zig#L697-L749](https://codeberg.org/ziglang/zig/src/commit/764760df62c63bc2a3d4bd4ec95c000233625834/lib/std/start.zig#L697-L749) ---
**Author:** ![Ahmad](https://ziggit.dev/user_avatar/ziggit.dev/ahmad/32/10010_2.png) [@Ahmad](https://ziggit.dev/u/Ahmad)\ **Post date:** [April 28, 2026, 6:47pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/14 "2026-04-28T18:47:21Z")
I forgot to check `start.zig` source code thank you for posting that. But still one does not pass an allocator parameter to allocate that memory, but sense it happens in `callMain()` I think it’s less bad because what! you want to pass an allocator the main function! Then, why even include it to begin with? what big problem does this exception to “In Zig if an API allocates memory then it must take an allocator” solve? I personally will not use `init.environ_map` I think the following is just fine … ```zig var environ_map = init.minimal.environ.createMap(gpa); defer environ_map.deinit(); ``` ---
**Author:** ![Ahmad](https://ziggit.dev/user_avatar/ziggit.dev/ahmad/32/10010_2.png) [@Ahmad](https://ziggit.dev/u/Ahmad)\ **Post date:** [April 28, 2026, 6:57pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/15 "2026-04-28T18:57:49Z")
It turned out `std.process.Init.environ_map` is not the only thing that allocates memory in `main`, great!!! ---
**Author:** ![vulpesx](https://ziggit.dev/user_avatar/ziggit.dev/vulpesx/32/3989_2.png) [@vulpesx](https://ziggit.dev/u/vulpesx)\ **Post date:** [April 29, 2026, 8:01am UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/16 "2026-04-29T08:01:39Z")
> [@Ahmad](#): > > ```zig > var environ_map = init.minimal.environ.createMap(gpa); > defer environ_map.deinit(); > > ``` that is literally what `init.environ_map` is, not only that, but your snippet is still using the full `std.process.Init` so `init.environ_map` still exists meaning your allocation is unecessary. If you were to use `std.process.Init.Minimal` as the parameter it would be fine, but to ask for the full thing, then duplicate what it does with no changes is just un optimal. ---
**Author:** ![Adau](https://ziggit.dev/user_avatar/ziggit.dev/adau/32/5320_2.png) [@Adau](https://ziggit.dev/u/Adau)\ **Post date:** [April 29, 2026, 8:18am UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/17 "2026-04-29T08:18:39Z")
`Juicy Main` is great to get things quickly, especially `allocator` and `io`. It’s a nice way to lower the barrier for newcomers to the language, as `Hello World` might have been frightening at first sight. I never saw `Juicy Main` as something else than pure convenience to start with. But at some point in a project, I assume it has to be removed, at least to choose from Threaded/Evented io. ---
**Author:** ![Ahmad](https://ziggit.dev/user_avatar/ziggit.dev/ahmad/32/10010_2.png) [@Ahmad](https://ziggit.dev/u/Ahmad)\ **Post date:** [April 29, 2026, 3:13pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/18 "2026-04-29T15:13:49Z")
Thank you for reminding me. I actually thought about using `Init.Minimal` but I got lazy replacing `init.io` and `init.gpa` (which picks an appropriate allocator not just `debug_allocator`). ---
**Author:** ![jmctagger](https://ziggit.dev/letter_avatar_proxy/v4/letter/j/8dc957/32.png) [@jmctagger](https://ziggit.dev/u/jmctagger)\ **Post date:** [April 29, 2026, 9:26pm UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/19 "2026-04-29T21:26:21Z")
> [@Ahmad](#): > > ```zig > const environ_map = init.environ_map; > defer environ_map.deinit(); > > ``` I don’t know if it’s just familiarity, but my knee-jerk reaction was, “why would you `deinit()` when you weren’t responsible for `init()`?” And I don’t even use juicy-main, and know very little about it! I think that what makes this “not hidden magic” is that symmetry. What would be “wrong”, for sure, is if I called `foo.init(gpa)` (or `create()` or whatever) and was informed, in a back alley, that I should NOT call `defer foo.deinit()`, or otherwise consider my responsibility for the resource that required an allocator to create/init. _That_ would be “bad magic” (which some might wrongly think “a nice convenience”, in the vein of GC). But juicy-main does feel like it’s supposed to be a batteries-included power-tool, so I’d enter into its use expecting it to do allocations, initializations, setups as well as the symmetric deallocations, deinitializations, and teardowns for me. I’d expect this with environ\_map, io, and the whole kitten kaboodle (unless std.process.Init.Minimal was used instead of the full .Init, apparently, as @vulpesx pointed out, and about which I knew nothing about before). ---
**Author:** ![Ahmad](https://ziggit.dev/user_avatar/ziggit.dev/ahmad/32/10010_2.png) [@Ahmad](https://ziggit.dev/u/Ahmad)\ **Post date:** [April 30, 2026, 2:49am UTC](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202/20 "2026-04-30T02:49:03Z")
That is besides the point I only included … ```zig const environ_map = init.environ_map; defer environ_map.deinit(); ``` in my question as I was telling my thought process, I was telling the whole story that led to my confusion. I don’t mean that should be the way. What I do think should be the way is … ```zig const environ_map = init.environ_map(gpa); defer environ_map.deinit(); ``` IMO, juicy main can still be batteries included with just, just, APIs that allocate memory to expect an allocator parameter, that is it. [Next page](https://ziggit.dev/t/does-std-process-init-environ-map-allocate-memory-or-not/15202.md?page=2)