utils: Move 'fcntl-flock' to (guix build syscalls).

* guix/utils.scm (%struct-flock, F_SETLKW, F_SETLK, F_xxLCK)
(fcntl-flock): Move to...
* guix/build/syscalls.scm: ... here.  New variables.
* guix/nar.scm: Adjust imports accordingly.
* tests/utils.scm ("fcntl-flock wait", "fcntl-flock non-blocking"): Move
to...
* tests/syscalls.scm: ... here.  New tests.
(temp-file): New variable.

3 files changed, 72 insertions, 76 deletions

diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index a9cd6e93c8..86723c23c7 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -65,6 +65,7 @@
             processes
             mkdtemp!
             pivot-root
+            fcntl-flock
 
             CLONE_CHILD_CLEARTID
             CLONE_CHILD_SETTID
@@ -639,6 +640,74 @@ system to PUT-OLD."
 
 
 ;;;
+;;; Advisory file locking.
+;;;
+
+(define %struct-flock
+  ;; 'struct flock' from <fcntl.h>.
+  (list short                                     ; l_type
+        short                                     ; l_whence
+        size_t                                    ; l_start
+        size_t                                    ; l_len
+        int))                                     ; l_pid
+
+(define F_SETLKW
+  ;; On Linux-based systems, this is usually 7, but not always
+  ;; (exceptions include SPARC.)  On GNU/Hurd, it's 9.
+  (cond ((string-contains %host-type "sparc") 9)  ; sparc-*-linux-gnu
+        ((string-contains %host-type "linux") 7)  ; *-linux-gnu
+        (else 9)))                                ; *-gnu*
+
+(define F_SETLK
+  ;; Likewise: GNU/Hurd and SPARC use 8, while the others typically use 6.
+  (cond ((string-contains %host-type "sparc") 8)  ; sparc-*-linux-gnu
+        ((string-contains %host-type "linux") 6)  ; *-linux-gnu
+        (else 8)))                                ; *-gnu*
+
+(define F_xxLCK
+  ;; The F_RDLCK, F_WRLCK, and F_UNLCK constants.
+  (cond ((string-contains %host-type "sparc") #(1 2 3))    ; sparc-*-linux-gnu
+        ((string-contains %host-type "hppa")  #(1 2 3))    ; hppa-*-linux-gnu
+        ((string-contains %host-type "linux") #(0 1 2))    ; *-linux-gnu
+        (else                                 #(1 2 3))))  ; *-gnu*
+
+(define fcntl-flock
+  (let ((proc (syscall->procedure int "fcntl" `(,int ,int *))))
+    (lambda* (fd-or-port operation #:key (wait? #t))
+      "Perform locking OPERATION on the file beneath FD-OR-PORT.  OPERATION
+must be a symbol, one of 'read-lock, 'write-lock, or 'unlock.  When WAIT? is
+true, block until the lock is acquired; otherwise, thrown an 'flock-error'
+exception if it's already taken."
+      (define (operation->int op)
+        (case op
+          ((read-lock)  (vector-ref F_xxLCK 0))
+          ((write-lock) (vector-ref F_xxLCK 1))
+          ((unlock)     (vector-ref F_xxLCK 2))
+          (else         (error "invalid fcntl-flock operation" op))))
+
+      (define fd
+        (if (port? fd-or-port)
+            (fileno fd-or-port)
+            fd-or-port))
+
+      ;; XXX: 'fcntl' is a vararg function, but here we happily use the
+      ;; standard ABI; crossing fingers.
+      (let ((err (proc fd
+                       (if wait?
+                           F_SETLKW               ; lock & wait
+                           F_SETLK)               ; non-blocking attempt
+                       (make-c-struct %struct-flock
+                                      (list (operation->int operation)
+                                            SEEK_SET
+                                            0 0   ; whole file
+                                            0)))))
+        (or (zero? err)
+
+            ;; Presumably we got EAGAIN or so.
+            (throw 'flock-error (errno)))))))
+
+
+;;;
 ;;; Network interfaces.
 ;;;
 
diff --git a/guix/nar.scm b/guix/nar.scm
index 43e5210752..739d3d3a57 100644
--- a/guix/nar.scm
+++ b/guix/nar.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014 Mark H Weaver <mhw@netris.org>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -18,8 +18,8 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (guix nar)
-  #:use-module (guix utils)
   #:use-module (guix serialization)
+  #:use-module (guix build syscalls)
   #:use-module ((guix build utils)
                 #:select (delete-file-recursively with-directory-excursion))
   #:use-module (guix store)
diff --git a/guix/utils.scm b/guix/utils.scm
index f18bbd19ac..d924e434bd 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -34,7 +34,7 @@
   #:use-module ((rnrs bytevectors) #:select (bytevector-u8-set!))
   #:use-module (guix combinators)
   #:use-module ((guix build utils) #:select (dump-port))
-  #:use-module ((guix build syscalls) #:select (errno mkdtemp!))
+  #:use-module ((guix build syscalls) #:select (mkdtemp!))
   #:use-module (ice-9 vlist)
   #:use-module (ice-9 format)
   #:autoload   (ice-9 popen)  (open-pipe*)
@@ -47,7 +47,6 @@
   #:export (bytevector->base16-string
             base16-string->bytevector
 
-            fcntl-flock
             strip-keyword-arguments
             default-keyword-arguments
             substitute-keyword-arguments
@@ -340,78 +339,6 @@ This procedure returns #t on success."
 
 
 ;;;
-;;; Advisory file locking.
-;;;
-
-(define %struct-flock
-  ;; 'struct flock' from <fcntl.h>.
-  (list short                                     ; l_type
-        short                                     ; l_whence
-        size_t                                    ; l_start
-        size_t                                    ; l_len
-        int))                                     ; l_pid
-
-(define F_SETLKW
-  ;; On Linux-based systems, this is usually 7, but not always
-  ;; (exceptions include SPARC.)  On GNU/Hurd, it's 9.
-  (compile-time-value
-   (cond ((string-contains %host-type "sparc") 9) ; sparc-*-linux-gnu
-         ((string-contains %host-type "linux") 7) ; *-linux-gnu
-         (else 9))))                              ; *-gnu*
-
-(define F_SETLK
-  ;; Likewise: GNU/Hurd and SPARC use 8, while the others typically use 6.
-  (compile-time-value
-   (cond ((string-contains %host-type "sparc") 8) ; sparc-*-linux-gnu
-         ((string-contains %host-type "linux") 6) ; *-linux-gnu
-         (else 8))))                              ; *-gnu*
-
-(define F_xxLCK
-  ;; The F_RDLCK, F_WRLCK, and F_UNLCK constants.
-  (compile-time-value
-   (cond ((string-contains %host-type "sparc") #(1 2 3))    ; sparc-*-linux-gnu
-         ((string-contains %host-type "hppa")  #(1 2 3))    ; hppa-*-linux-gnu
-         ((string-contains %host-type "linux") #(0 1 2))    ; *-linux-gnu
-         (else                                 #(1 2 3))))) ; *-gnu*
-
-(define fcntl-flock
-  (let* ((ptr  (dynamic-func "fcntl" (dynamic-link)))
-         (proc (pointer->procedure int ptr `(,int ,int *))))
-    (lambda* (fd-or-port operation #:key (wait? #t))
-      "Perform locking OPERATION on the file beneath FD-OR-PORT.  OPERATION
-must be a symbol, one of 'read-lock, 'write-lock, or 'unlock.  When WAIT? is
-true, block until the lock is acquired; otherwise, thrown an 'flock-error'
-exception if it's already taken."
-      (define (operation->int op)
-        (case op
-          ((read-lock)  (vector-ref F_xxLCK 0))
-          ((write-lock) (vector-ref F_xxLCK 1))
-          ((unlock)     (vector-ref F_xxLCK 2))
-          (else         (error "invalid fcntl-flock operation" op))))
-
-      (define fd
-        (if (port? fd-or-port)
-            (fileno fd-or-port)
-            fd-or-port))
-
-      ;; XXX: 'fcntl' is a vararg function, but here we happily use the
-      ;; standard ABI; crossing fingers.
-      (let ((err (proc fd
-                       (if wait?
-                           F_SETLKW               ; lock & wait
-                           F_SETLK)               ; non-blocking attempt
-                       (make-c-struct %struct-flock
-                                      (list (operation->int operation)
-                                            SEEK_SET
-                                            0 0   ; whole file
-                                            0)))))
-        (or (zero? err)
-
-            ;; Presumably we got EAGAIN or so.
-            (throw 'flock-error (errno)))))))
-
-
-;;;
 ;;; Keyword arguments.
 ;;;