Re: Fixed output derivation hash mismatch - why?

[Mark H Weaver <mhw@netris.org>]

Hi Chris,

Chris Marusich <cmmarusich@gmail.com> writes:

> I'm trying to define a fixed output derivation using gexp->derivation,
> but I'm getting a hash mismatch, and I can't figure out why.  I've
> attached a minimal script that illustrates the problem.  When I run it,
> I see the following output:
>
> $ /tmp/test-fixed-output-derivation.scm 
> ;;; note: auto-compilation is enabled, set GUILE_AUTO_COMPILE=0
> ;;;       or pass the --no-auto-compile argument to disable.
> ;;; compiling /tmp/test-fixed-output-derivation.scm
> ;;; compiled /home/marusich/.cache/guile/ccache/2.2-LE-8-3.A/tmp/test-fixed-output-derivation.scm.go
> The following derivation will be built:
>    /gnu/store/fiiz8cxz90q7l0c6jfdrpzkanyyvhpv8-test.drv
> building path(s) `/gnu/store/8s4m28x6qmpkqhqasy59lw3hih548kxv-test'
> `/gnu/store/kfzwabhn37bg692ayb2czb853drlv2gp-test' -> `/gnu/store/8s4m28x6qmpkqhqasy59lw3hih548kxv-test'
> sha256 hash mismatch for output path `/gnu/store/8s4m28x6qmpkqhqasy59lw3hih548kxv-test'
>   expected: 0dids4n73p8w77pn9nffs7x0ww1a3f1jbic1p642hwd0jfl3zcg9
>   actual:   1r3v22qkypccqifzbww5lrn6hf1chi23m6zzkyvb8bvg457nxslq
> Backtrace:
>            8 (apply-smob/1 #<catch-closure 2507640>)
> In ice-9/boot-9.scm:
>     705:2  7 (call-with-prompt _ _ #<procedure default-prompt-handle…>)
> In ice-9/eval.scm:
>     619:8  6 (_ #(#(#<directory (guile-user) 25be140>)))
> In ice-9/boot-9.scm:
>    2312:4  5 (save-module-excursion _)
>   3822:12  4 (_)
> In /tmp/test-fixed-output-derivation.scm:
>      30:2  3 (_)
> In guix/store.scm:
>   1443:24  2 (run-with-store _ _ #:guile-for-build _ #:system _ # _)
>   1362:38  1 (_ #<build-daemon 256.97 2bd1eb0>)
>    936:15  0 (_ #<build-daemon 256.97 2bd1eb0> _ _)
>
> guix/store.scm:936:15: Throw to key `srfi-34' with args `(#<condition &nix-protocol-error [message: "build of `/gnu/store/fiiz8cxz90q7l0c6jfdrpzkanyyvhpv8-test.drv' failed" status: 1] 33c9030>)'.
>
> I don't understand why the Guix daemon thinks that the output
> (/gnu/store/8s4m28x6qmpkqhqasy59lw3hih548kxv-test) hashes to
> 0dids4n73p8w77pn9nffs7x0ww1a3f1jbic1p642hwd0jfl3zcg9.

It doesn't.  When the daemon writes:

   expected: 0dids4n73p8w77pn9nffs7x0ww1a3f1jbic1p642hwd0jfl3zcg9
   actual:   1r3v22qkypccqifzbww5lrn6hf1chi23m6zzkyvb8bvg457nxslq

that means that the output hashes to
1r3v22qkypccqifzbww5lrn6hf1chi23m6zzkyvb8bvg457nxslq, but you told it to
expect 0dids4n73p8w77pn9nffs7x0ww1a3f1jbic1p642hwd0jfl3zcg9.

> That doesn't even
> match what "guix hash" says:
>
>   $ guix hash /gnu/store/8s4m28x6qmpkqhqasy59lw3hih548kxv-test
>   1r3v22qkypccqifzbww5lrn6hf1chi23m6zzkyvb8bvg457nxslq

Yes it does.  This matches what the daemon wrote was the "actual" hash.

> Note that the result of "guix hash" above DOES match the hash value for
> /tmp/test:
>
>   $ guix hash /tmp/test
>   1r3v22qkypccqifzbww5lrn6hf1chi23m6zzkyvb8bvg457nxslq

It matches both of them.

> What's going on here?

I think the problem is here:

  (define hash (sha256
                (base32
                 "1r3v22qkypccqifzbww5lrn6hf1chi23m6zzkyvb8bvg457nxslq")))

Remove the 'sha256'.  It should just be this:

  (define hash (base32
                "1r3v22qkypccqifzbww5lrn6hf1chi23m6zzkyvb8bvg457nxslq"))

Within 'origin' records, the 'sha256' is the field name, part of the
constructor syntax.  Here, you are not within an 'origin' constructor,
and the 'sha256' is instead a procedure which computes the sha256 hash
of its argument.

      Mark