1 files changed, 48 insertions, 29 deletions

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index ef2f7adf3194..6f02762442a1 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -961,6 +961,16 @@ PathSet outputPaths(const DerivationOutputs & outputs)
 }
 
 
+static bool canBuildLocally(const string & platform)
+{
+    return platform == thisSystem 
+#ifdef CAN_DO_LINUX32_BUILDS
+        || (platform == "i686-linux" && thisSystem == "x86_64-linux")
+#endif
+        ;
+}
+
+
 void DerivationGoal::tryToBuild()
 {
     trace("trying to build");
@@ -1028,28 +1038,38 @@ void DerivationGoal::tryToBuild()
     foreach (DerivationOutputs::iterator, i, drv.outputs)
         if (pathFailed(i->second.path)) return;
 
+    /* Don't do a remote build if the derivation has the attribute
+       `preferLocalBuild' set. */
+    bool preferLocalBuild =
+        drv.env["preferLocalBuild"] == "1" && canBuildLocally(drv.platform);
+
     /* Is the build hook willing to accept this job? */
-    usingBuildHook = true;
-    switch (tryBuildHook()) {
-        case rpAccept:
-            /* Yes, it has started doing so.  Wait until we get EOF
-               from the hook. */
-            state = &DerivationGoal::buildDone;
-            return;
-        case rpPostpone:
-            /* Not now; wait until at least one child finishes. */
-            worker.waitForAWhile(shared_from_this());
-            outputLocks.unlock();
-            return;
-        case rpDecline:
-            /* We should do it ourselves. */
-            break;
+    if (!preferLocalBuild) {
+        usingBuildHook = true;
+        switch (tryBuildHook()) {
+            case rpAccept:
+                /* Yes, it has started doing so.  Wait until we get
+                   EOF from the hook. */
+                state = &DerivationGoal::buildDone;
+                return;
+            case rpPostpone:
+                /* Not now; wait until at least one child finishes. */
+                worker.waitForAWhile(shared_from_this());
+                outputLocks.unlock();
+                return;
+            case rpDecline:
+                /* We should do it ourselves. */
+                break;
+        }
     }
-
+    
     usingBuildHook = false;
 
-    /* Make sure that we are allowed to start a build. */
-    if (worker.getNrLocalBuilds() >= maxBuildJobs) {
+    /* Make sure that we are allowed to start a build.  If this
+       derivation prefers to be done locally, do it even if
+       maxBuildJobs is 0. */
+    unsigned int curBuilds = worker.getNrLocalBuilds();
+    if (curBuilds >= maxBuildJobs && !(preferLocalBuild && curBuilds == 0)) {
         worker.waitForBuildSlot(shared_from_this());
         outputLocks.unlock();
         return;
@@ -1380,11 +1400,7 @@ void DerivationGoal::startBuilder()
         format("building path(s) %1%") % showPaths(outputPaths(drv.outputs)))
     
     /* Right platform? */
-    if (drv.platform != thisSystem 
-#ifdef CAN_DO_LINUX32_BUILDS
-        && !(drv.platform == "i686-linux" && thisSystem == "x86_64-linux")
-#endif
-        )
+    if (!canBuildLocally(drv.platform))
         throw Error(
             format("a `%1%' is required to build `%3%', but I am a `%2%'")
             % drv.platform % thisSystem % drvPath);
@@ -1549,6 +1565,9 @@ void DerivationGoal::startBuilder()
 
     if (fixedOutput) useChroot = false;
 
+    /* Hack to allow derivations to disable chroot builds. */
+    if (drv.env["__noChroot"] == "1") useChroot = false;
+
     if (useChroot) {
 #if CHROOT_ENABLED
         /* Create a temporary directory in which we set up the chroot
@@ -1572,7 +1591,7 @@ void DerivationGoal::startBuilder()
 
         /* Create a /etc/passwd with entries for the build user and the
            nobody account.  The latter is kind of a hack to support
-           Samba-in-QEMU.  */
+           Samba-in-QEMU. */
         createDirs(chrootRootDir + "/etc");
 
         writeFile(chrootRootDir + "/etc/passwd",
@@ -1580,13 +1599,13 @@ void DerivationGoal::startBuilder()
                 "nixbld:x:%1%:%2%:Nix build user:/:/noshell\n"
                 "nobody:x:65534:65534:Nobody:/:/noshell\n")
                 % (buildUser.enabled() ? buildUser.getUID() : getuid())
-	        % (buildUser.enabled() ? buildUser.getGID() : getgid())).str());
+                % (buildUser.enabled() ? buildUser.getGID() : getgid())).str());
 
 	/* Declare the build user's group so that programs get a consistent
-	   view of the system (e.g., "id -gn").  */
-	writeFile(chrootRootDir + "/etc/group",
-		  (format("nixbld:!:%1%:\n")
-		   % (buildUser.enabled() ? buildUser.getGID() : getgid())).str());
+	   view of the system (e.g., "id -gn"). */
+        writeFile(chrootRootDir + "/etc/group",
+            (format("nixbld:!:%1%:\n")
+                % (buildUser.enabled() ? buildUser.getGID() : getgid())).str());
 
         /* Bind-mount a user-configurable set of directories from the
            host file system.  The `/dev/pts' directory must be mounted