Re: 'make clean' followed by 'make' in the same Nix shell doesn't work

Demi Marie Obenour
2025-08-05T19:47:28Z

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On 8/5/25 15:33, Alyssa Ross wrote:
> Demi Marie Obenour <demiobenour@gmail.com> writes:
>
>> On 7/29/25 08:33, Alyssa Ross wrote:
>>> Demi Marie Obenour <demiobenour@gmail.com> writes:
>>>
>>>> The following command fails to rebuild the image:
>>>>
>>>> $ nix-shell --run 'make clean && make run-qemu'
>>>>
>>>> The following command succeeds:
>>>>
>>>> $ nix-shell --pure --run 'make clean' && nix-shell --pure --run 'make run-qemu'
>>>>
>>>> Interactive Nix shells exhibit the same problems, and adding
>>>> --pure to the first invocation does not help.
>>>
>>> Works for me on 560fd87 in img/app. What were you testing? Logs?
>>
>> I think the problem only arises when there is a dependency that
>> default.nix knows about but the makefile doesn't. nix-shell
>> appears to import default.nix directly, so
>>
>> $ nix-build default.nix
>>
>> inside a Nix shell does not update various paths (like the path
>> to the kernel) that the makefile needs.
>>
>> I think it would be better for the makefile to import the
>> variables from Nix if possible.
>
> Yeah, that's not how it works. You need to exit and re-enter the shell.
> nix-build will not update your shell environment, and that's where Make
> variables come from.

Ack. I think it is best to recommend (perhaps in the docs?) that one run
`nix-shell --pure --run 'make THINGS'`, which avoids all of these problems.
Providing a that did that would be ideal and should be fairly straightforward.
Using an interactive shell can be an optimization, but it can also result in
silently broken builds for at least the reason you mentioned, so I think it
is best to discourage it except in the repository root.