bug#61055: file-needed/recurive does not canonicalize paths

[Lars-Dominik Braun]

Hi,

(CC-ing Ludo, who wrote the code according to git logs)

during testing of wip-haskell I observed the make-dynamic-linker-cache
phase is taking alot of time (up to two minutes on a fast machine with
SSD). Looking at ghc-hindent for example [1]:

    starting phase `make-dynamic-linker-cache'
    created 
'/gnu/store/2nrzbaxmqs2rq9yv52bpyn2azb3qj6h1-ghc-hindent-5.3.4/etc/ld.so.cache' 
from 10085 library search path entries
    phase `make-dynamic-linker-cache' succeeded after 119.5 seconds

And while Haskell packages link to a pretty large number of dynamic
libraries (116 in this case), 10000 search path entries seems wrong. Running 
just

    (file-needed/recursive 
"/gnu/store/2nrzbaxmqs2rq9yv52bpyn2azb3qj6h1-ghc-hindent-5.3.4/bin/hindent")

takes a long time and reveals entries like
/gnu/store/1cyk8j2nd6r0cvm6kx1408kd763yf8h5-ghc-9.2.5/lib/ghc-9.2.5/Cabal-3.6.3.0/../directory-1.3.6.2/../unix-2.7.2.2/../bytestring-0.11.3.1/../template-haskell-2.18.0.0/../pretty-1.1.3.6/../array-0.5.4.0/../base-4.16.4.0/../ghc-bignum-1.2/../ghc-prim-0.8.0/libHSghc-prim-0.8.0-ghc9.2.5.so
so it looks like it deduplicates values, but does not canonicalize
paths. A relatively straight-forward fix could be the following change,
but I don’t know if that would cause any issues, since canonicalize-path
throws an exception if the resulting path does not exist. It’s also
a world rebuild since pretty much any package uses this phase (and the
reason and I cannot test it on a larger scale).

---snip---
diff --git a/guix/build/gremlin.scm b/guix/build/gremlin.scm
index 2a74d51dd9..6eb8f688ea 100644
--- a/guix/build/gremlin.scm
+++ b/guix/build/gremlin.scm
@@ -285,8 +285,8 @@ (define (file-needed/recursive file)
             (if (and runpath needed)
                 (let* ((runpath  (map (cute expand-origin <> (dirname file))
                                       runpath))
-                       (resolved (map (cut search-path runpath <>)
-                                      needed))
+                       (resolved (map (lambda (x) (and=> x canonicalize-path)) 
(map (cut search-path runpath <>)
+                                      needed)))
                        (failed   (filter-map (lambda (needed resolved)
                                                (and (not resolved)
                                                     (not (libc-library? 
needed))
---snap---

Cheers,
Lars

[1] https://ci.guix.gnu.org/build/366156/log/raw