* Sync with the trunk.

src/libstore/build.cc

@@ -25,6 +25,7 @@
 #include <unistd.h>
 #include <errno.h>
 #include <stdio.h>
+#include <cstring>
 
 #include <pwd.h>
 #include <grp.h>
@@ -1427,6 +1428,9 @@ void DerivationGoal::startBuilder()
        in the store or in the build directory). */
     env["NIX_STORE"] = nixStore;
 
+    /* The maximum number of cores to utilize for parallel building. */
+    env["NIX_BUILD_CORES"] = (format("%d") % buildCores).str();
+
     /* Add all bindings specified in the derivation. */
     foreach (StringPairs::iterator, i, drv.env)
         env[i->first] = i->second;
@@ -2654,6 +2658,7 @@ void Worker::waitForInput()
         timeout.tv_sec = std::max((time_t) 0, lastWokenUp + wakeUpInterval - before);
     } else lastWokenUp = 0;
 
+    using namespace std;
     /* Use select() to wait for the input side of any logger pipe to
        become `available'.  Note that `available' (i.e., non-blocking)
        includes EOF. */

src/libstore/globals.cc

@@ -22,6 +22,7 @@ bool keepGoing = false;
 bool tryFallback = false;
 Verbosity buildVerbosity = lvlInfo;
 unsigned int maxBuildJobs = 1;
+unsigned int buildCores = 1;
 bool readOnlyMode = false;
 string thisSystem = "unset";
 time_t maxSilentTime = 0;

src/libstore/globals.hh

@@ -55,6 +55,11 @@ extern Verbosity buildVerbosity;
 /* Maximum number of parallel build jobs.  0 means unlimited. */
 extern unsigned int maxBuildJobs;
 
+/* Number of CPU cores to utilize in parallel within a build, i.e. by passing
+   this number to Make via '-j'. 0 means that the number of actual CPU cores on
+   the local host ought to be auto-detected. */
+extern unsigned int buildCores;
+
 /* Read-only mode.  Don't copy stuff to the store, don't change the
    database. */
 extern bool readOnlyMode;

src/libstore/remote-store.cc

@@ -13,6 +13,7 @@
 
 #include <iostream>
 #include <unistd.h>
+#include <cstring>
 
 
 namespace nix {
@@ -158,6 +159,7 @@ void RemoteStore::connectToDaemon()
     addr.sun_family = AF_UNIX;
     if (socketPathRel.size() >= sizeof(addr.sun_path))
         throw Error(format("socket path `%1%' is too long") % socketPathRel);
+    using namespace std;
     strcpy(addr.sun_path, socketPathRel.c_str());
     
     if (connect(fdSocket, (struct sockaddr *) &addr, sizeof(addr)) == -1)