3 files changed, 39 insertions, 6 deletions
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 2998506b5821..e2f5b087f13f 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -927,7 +927,7 @@ string runProgram(Path program, bool searchPath, const Strings & args,
     /* Wait for the child to finish. */
     int status = pid.wait(true);
     if (!statusOk(status))
-        throw ExecError(format("program ‘%1%’ %2%")
+        throw ExecError(status, format("program ‘%1%’ %2%")
             % program % statusToString(status));
 
     return result;
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 1a43bf400a03..259c73260da3 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -247,7 +247,16 @@ pid_t startProcess(std::function<void()> fun, const ProcessOptions & options = P
 string runProgram(Path program, bool searchPath = false,
     const Strings & args = Strings(), const string & input = "");
 
-MakeError(ExecError, Error)
+class ExecError : public Error
+{
+public:
+    int status;
+
+    template<typename... Args>
+    ExecError(int status, Args... args)
+        : Error(args...), status(status)
+    { }
+};
 
 /* Convert a list of strings to a null-terminated vector of char
    *'s. The result must not be accessed beyond the lifetime of the
diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index eb5719e47fb2..b209464b8279 100755
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -60,6 +60,14 @@ std::vector<string> shellwords(const string & s)
     return res;
 }
 
+static void maybePrintExecError(ExecError & e)
+{
+    if (WIFEXITED(e.status))
+        throw Exit(WEXITSTATUS(e.status));
+    else
+        throw e;
+}
+
 int main(int argc, char ** argv)
 {
     return handleExceptions(argv[0], [&]() {
@@ -346,8 +354,12 @@ int main(int argc, char ** argv)
                 for (const auto & arg : instArgs)
                     instantiateArgs.push_back(arg);
                 instantiateArgs.push_back(expr);
-                auto instOutput = runProgram(settings.nixBinDir + "/nix-instantiate", false, instantiateArgs);
-                drvPaths = tokenizeString<std::vector<string>>(instOutput);
+                try {
+                    auto instOutput = runProgram(settings.nixBinDir + "/nix-instantiate", false, instantiateArgs);
+                    drvPaths = tokenizeString<std::vector<string>>(instOutput);
+                } catch (ExecError & e) {
+                    maybePrintExecError(e);
+                }
             } else {
                 drvPaths.push_back(expr);
             }
@@ -370,7 +382,12 @@ int main(int argc, char ** argv)
                         nixStoreArgs.push_back(input.first);
                 for (const auto & src : drv.inputSrcs)
                     nixStoreArgs.push_back(src);
-                runProgram(settings.nixBinDir + "/nix-store", false, nixStoreArgs);
+
+                try {
+                    runProgram(settings.nixBinDir + "/nix-store", false, nixStoreArgs);
+                } catch (ExecError & e) {
+                    maybePrintExecError(e);
+                }
 
                 // Set the environment.
                 auto env = getEnv();
@@ -471,7 +488,14 @@ int main(int argc, char ** argv)
                 nixStoreArgs.push_back(arg);
             for (const auto & path : drvPaths2)
                 nixStoreArgs.push_back(path);
-            auto nixStoreRes = runProgram(settings.nixBinDir + "/nix-store", false, nixStoreArgs);
+
+            std::string nixStoreRes;
+            try {
+                nixStoreRes = runProgram(settings.nixBinDir + "/nix-store", false, nixStoreArgs);
+            } catch (ExecError & e) {
+                maybePrintExecError(e);
+            }
+
             for (const auto & outpath : tokenizeString<std::vector<string>>(nixStoreRes))
                 outPaths.push_back(chomp(outpath));