1 files changed, 13 insertions, 9 deletions
diff --git a/src/libstore/builtins/buildenv.cc b/src/libstore/builtins/buildenv.cc
index 7bba33fb9..c8911d153 100644
--- a/src/libstore/builtins/buildenv.cc
+++ b/src/libstore/builtins/buildenv.cc
@@ -174,15 +174,19 @@ void builtinBuildenv(const BasicDerivation & drv)
     /* Convert the stuff we get from the environment back into a
      * coherent data type. */
     Packages pkgs;
-    auto derivations = tokenizeString<Strings>(getAttr("derivations"));
-    while (!derivations.empty()) {
-        /* !!! We're trusting the caller to structure derivations env var correctly */
-        auto active = derivations.front(); derivations.pop_front();
-        auto priority = stoi(derivations.front()); derivations.pop_front();
-        auto outputs = stoi(derivations.front()); derivations.pop_front();
-        for (auto n = 0; n < outputs; n++) {
-            auto path = derivations.front(); derivations.pop_front();
-            pkgs.emplace_back(path, active != "false", priority);
+    {
+        auto derivations = tokenizeString<Strings>(getAttr("derivations"));
+
+        auto itemIt = derivations.begin();
+        while (itemIt != derivations.end()) {
+            /* !!! We're trusting the caller to structure derivations env var correctly */
+            const bool active = "false" != *itemIt++;
+            const int priority = stoi(*itemIt++);
+            const size_t outputs = stoul(*itemIt++);
+
+            for (size_t n {0}; n < outputs; n++) {
+                pkgs.emplace_back(std::move(*itemIt++), active, priority);
+            }
         }
     }