Merge branch 'master' into make

Conflicts:
	src/libexpr/eval.cc

1 files changed, 6 insertions, 2 deletions

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 63e34d256057..4329d9a22b95 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -1011,7 +1011,7 @@ void DerivationGoal::outputsSubstituted()
     trace("all outputs substituted (maybe)");
 
     if (nrFailed > 0 && nrFailed > nrNoSubstituters + nrIncompleteClosure && !settings.tryFallback)
-        throw Error(format("some substitutes for the outputs of derivation `%1%' failed; try `--fallback'") % drvPath);
+        throw Error(format("some substitutes for the outputs of derivation `%1%' failed (usually happens due to networking issues); try `--fallback' to build derivation from source ") % drvPath);
 
     /*  If the substitutes form an incomplete closure, then we should
         build the dependencies of this derivation, but after that, we
@@ -1623,10 +1623,13 @@ void DerivationGoal::startBuilder()
     startNest(nest, lvlInfo, format(repair ? "repairing path(s) %1%" : "building path(s) %1%") % showPaths(missingPaths));
 
     /* Right platform? */
-    if (!canBuildLocally(drv.platform))
+    if (!canBuildLocally(drv.platform)) {
+        if (settings.printBuildTrace)
+            printMsg(lvlError, format("@ unsupported-platform %1% %2%") % drvPath % drv.platform);
         throw Error(
             format("a `%1%' is required to build `%3%', but I am a `%2%'")
             % drv.platform % settings.thisSystem % drvPath);
+    }
 
     /* Construct the environment passed to the builder. */
 
@@ -2746,6 +2749,7 @@ void SubstitutionGoal::finished()
     logPipe.readSide.close();
 
     /* Get the hash info from stdout. */
+    string dummy = readLine(outPipe.readSide);
     string expectedHashStr = statusOk(status) ? readLine(outPipe.readSide) : "";
     outPipe.readSide.close();