build: Capture configure-time settings in (guix config).

* configure.ac: Compute and substitute `guix_localstatedir'.
* m4/guix.m4: Substitute `guix_system'.
* guix/config.scm.in (%store-directory, %store-directory, %system): New
  variables.
* guix/store.scm (%nix-state-dir): Remove.
  (%default-socket-path): Use %STATE-DIRECTORY as the default.
  (%store-prefix): Use %STORE-DIRECTORY as the default.
* guix/utils.scm (%current-system): Default to %SYSTEM.

configure.ac

@@ -30,6 +30,11 @@ AC_ARG_WITH(store-dir,
   [storedir="/nix/store"])
 AC_SUBST(storedir)
 
+# Prepare a version of $localstatedir that does not contain references
+# to shell variables.
+guix_localstatedir="`eval echo $localstatedir | sed -e "s|NONE|/usr/local|g"`"
+AC_SUBST([guix_localstatedir])
+
 PKG_CHECK_MODULES([GUILE], [guile-2.0])
 AC_PATH_PROG([GUILE], [guile])
 AC_PATH_PROG([GUILD], [guild])

guix/config.scm.in

@@ -20,6 +20,9 @@ (define-module (guix config)
   #:export (%guix-package-name
             %guix-version
             %guix-bug-report-address
+            %store-directory
+            %state-directory
+            %system
             %libgcrypt
             %nixpkgs
             %nix-instantiate))
@@ -39,6 +42,15 @@ (define %guix-version
 (define %guix-bug-report-address
   "@PACKAGE_BUGREPORT@")
 
+(define %store-directory
+  "@storedir@")
+
+(define %state-directory
+  "@guix_localstatedir@")
+
+(define %system
+  "@guix_system@")
+
 (define %libgcrypt
   "@LIBGCRYPT@")
 

guix/store.scm

@@ -18,6 +18,7 @@
 
 (define-module (guix store)
   #:use-module (guix utils)
+  #:use-module (guix config)
   #:use-module (rnrs bytevectors)
   #:use-module (rnrs io ports)
   #:use-module (srfi srfi-1)
@@ -111,10 +112,9 @@ (define-enumerate-type hash-algo
   (sha1 2)
   (sha256 3))
 
-(define %nix-state-dir
-  (or (getenv "NIX_STATE_DIR") "/nix/var/nix"))
 (define %default-socket-path
-  (string-append %nix-state-dir "/daemon-socket/socket"))
+  (string-append (or (getenv "NIX_STATE_DIR") %state-directory)
+                 "/daemon-socket/socket"))
 
 
 ;; serialize.cc
@@ -439,7 +439,7 @@ (define-operation (add-indirect-root (string file-name))
 (define %store-prefix
   ;; Absolute path to the Nix store.
   (make-parameter (or (and=> (getenv "NIX_STORE_DIR") canonicalize-path)
-                      "/nix/store")))
+                      %store-directory)))
 
 (define (store-path? path)
   "Return #t if PATH is a store path."

guix/utils.scm

@@ -342,7 +342,8 @@ (define (gnu-triplet->nix-system triplet)
 
 (define %current-system
   ;; System type as expected by Nix, usually ARCHITECTURE-KERNEL.
-  (make-parameter (gnu-triplet->nix-system %host-type)))
+  ;; By default, this is equal to (gnu-triplet->nix-system %host-type).
+  (make-parameter %system))
 
 (define (package-name->name+version name)
   "Given NAME, a package name like \"foo-0.9.1b\", return two values:

m4/guix.m4

@@ -61,4 +61,5 @@ AC_DEFUN([GUIX_SYSTEM_TYPE], [
 	  # `darwin10.2.0', etc.
 	  guix_system="$machine_name-`echo $host_os | "$SED" -e's/@<:@0-9.@:>@*$//g'`";;
      esac])
+  AC_SUBST([guix_system])
 ])