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-rw-r--r--third_party/nix/src/libexpr/attr-path.cc2
-rw-r--r--third_party/nix/src/libexpr/eval.cc89
-rw-r--r--third_party/nix/src/libexpr/eval.hh11
-rw-r--r--third_party/nix/src/libexpr/get-drvs.cc20
-rw-r--r--third_party/nix/src/libexpr/json-to-value.cc4
-rw-r--r--third_party/nix/src/libexpr/primops.cc158
-rw-r--r--third_party/nix/src/libexpr/primops/context.cc4
-rw-r--r--third_party/nix/src/libexpr/primops/fromTOML.cc6
-rw-r--r--third_party/nix/src/libexpr/value-to-json.cc7
-rw-r--r--third_party/nix/src/libexpr/value-to-xml.cc8
-rw-r--r--third_party/nix/src/libexpr/value.hh37
-rw-r--r--third_party/nix/src/libstore/worker-protocol.hh4
-rw-r--r--third_party/nix/src/nix-env/nix-env.cc7
-rw-r--r--third_party/nix/src/nix-env/user-env.cc24
-rw-r--r--third_party/nix/src/nix-prefetch-url/nix-prefetch-url.cc5
-rw-r--r--third_party/nix/src/nix/repl.cc8
16 files changed, 163 insertions, 231 deletions
diff --git a/third_party/nix/src/libexpr/attr-path.cc b/third_party/nix/src/libexpr/attr-path.cc
index e366f18575e7..a267e82b6ebe 100644
--- a/third_party/nix/src/libexpr/attr-path.cc
+++ b/third_party/nix/src/libexpr/attr-path.cc
@@ -99,7 +99,7 @@ Value* findAlongAttrPath(EvalState& state, const std::string& attrPath,
             attrIndex % attrPath);
       }
 
-      v = v->listElems()[attrIndex];
+      v = (*v->list)[attrIndex];
     }
   }
 
diff --git a/third_party/nix/src/libexpr/eval.cc b/third_party/nix/src/libexpr/eval.cc
index 16e6907214c9..f35f56c83c7d 100644
--- a/third_party/nix/src/libexpr/eval.cc
+++ b/third_party/nix/src/libexpr/eval.cc
@@ -97,12 +97,10 @@ static void printValue(std::ostream& str, std::set<const Value*>& active,
       str << "}";
       break;
     }
-    case tList1:
-    case tList2:
-    case tListN:
+    case tList:
       str << "[ ";
       for (unsigned int n = 0; n < v.listSize(); ++n) {
-        printValue(str, active, *v.listElems()[n]);
+        printValue(str, active, *(*v.list)[n]);
         str << " ";
       }
       str << "]";
@@ -162,9 +160,7 @@ std::string showType(const Value& v) {
       return "null";
     case tAttrs:
       return "a set";
-    case tList1:
-    case tList2:
-    case tListN:
+    case tList:
       return "a list";
     case tThunk:
       return "a thunk";
@@ -641,19 +637,15 @@ Env& EvalState::allocEnv(size_t size) {
   return *env;
 }
 
-void EvalState::mkList(Value& v, size_t size) {
+void EvalState::mkList(Value& v, NixList* list) {
   clearValue(v);
-  if (size == 1) {
-    v.type = tList1;
-  } else if (size == 2) {
-    v.type = tList2;
-  } else {
-    v.type = tListN;
-    v.bigList.size = size;
-    v.bigList.elems =
-        size != 0u ? (Value**)allocBytes(size * sizeof(Value*)) : nullptr;
-  }
-  nrListElems += size;
+  v.type = tList;
+  v.list = list;
+  nrListElems += list->size();
+}
+
+void EvalState::mkList(Value& v, size_t size) {
+  EvalState::mkList(v, new (GC) NixList(size));
 }
 
 unsigned long nrThunks = 0;
@@ -877,7 +869,7 @@ void ExprLet::eval(EvalState& state, Env& env, Value& v) {
 void ExprList::eval(EvalState& state, Env& env, Value& v) {
   state.mkList(v, elems.size());
   for (size_t n = 0; n < elems.size(); ++n) {
-    v.listElems()[n] = elems[n]->maybeThunk(state, env);
+    (*v.list)[n] = elems[n]->maybeThunk(state, env);
   }
 }
 
@@ -1252,39 +1244,21 @@ void ExprOpConcatLists::eval(EvalState& state, Env& env, Value& v) {
   e1->eval(state, env, v1);
   Value v2;
   e2->eval(state, env, v2);
-  Value* lists[2] = {&v1, &v2};
-  state.concatLists(v, 2, lists, pos);
+  state.concatLists(v, {&v1, &v2}, pos);
 }
 
-void EvalState::concatLists(Value& v, size_t nrLists, Value** lists,
-                            const Pos& pos) {
+void EvalState::concatLists(Value& v, const NixList& lists, const Pos& pos) {
   nrListConcats++;
 
-  Value* nonEmpty = nullptr;
-  size_t len = 0;
-  for (size_t n = 0; n < nrLists; ++n) {
-    forceList(*lists[n], pos);
-    auto l = lists[n]->listSize();
-    len += l;
-    if (l != 0u) {
-      nonEmpty = lists[n];
-    }
-  }
+  auto outlist = new (GC) NixList();
 
-  if ((nonEmpty != nullptr) && len == nonEmpty->listSize()) {
-    v = *nonEmpty;
-    return;
+  size_t len = 0;
+  for (Value* list : lists) {
+    forceList(*list, pos);
+    outlist->insert(outlist->end(), list->list->begin(), list->list->end());
   }
 
-  mkList(v, len);
-  auto out = v.listElems();
-  for (size_t n = 0, pos = 0; n < nrLists; ++n) {
-    auto l = lists[n]->listSize();
-    if (l != 0u) {
-      memcpy(out + pos, lists[n]->listElems(), l * sizeof(Value*));
-    }
-    pos += l;
-  }
+  mkList(v, outlist);
 }
 
 void ExprConcatStrings::eval(EvalState& state, Env& env, Value& v) {
@@ -1383,7 +1357,7 @@ void EvalState::forceValueDeep(Value& v) {
       }
     } else if (v.isList()) {
       for (size_t n = 0; n < v.listSize(); ++n) {
-        recurse(*v.listElems()[n]);
+        recurse(*(*v.list)[n]);
       }
     }
   };
@@ -1563,12 +1537,11 @@ std::string EvalState::coerceToString(const Pos& pos, Value& v,
     if (v.isList()) {
       std::string result;
       for (size_t n = 0; n < v.listSize(); ++n) {
-        result += coerceToString(pos, *v.listElems()[n], context, coerceMore,
+        result += coerceToString(pos, *(*v.list)[n], context, coerceMore,
                                  copyToStore);
         if (n < v.listSize() - 1
             /* !!! not quite correct */
-            && (!v.listElems()[n]->isList() ||
-                v.listElems()[n]->listSize() != 0)) {
+            && (!(*v.list)[n]->isList() || (*v.list)[n]->listSize() != 0)) {
           result += " ";
         }
       }
@@ -1653,14 +1626,12 @@ bool EvalState::eqValues(Value& v1, Value& v2) {
     case tNull:
       return true;
 
-    case tList1:
-    case tList2:
-    case tListN:
+    case tList:
       if (v1.listSize() != v2.listSize()) {
         return false;
       }
       for (size_t n = 0; n < v1.listSize(); ++n) {
-        if (!eqValues(*v1.listElems()[n], *v2.listElems()[n])) {
+        if (!eqValues(*(*v1.list)[n], *(*v2.list)[n])) {
           return false;
         }
       }
@@ -1883,14 +1854,12 @@ size_t valueSize(Value& v) {
           }
         }
         break;
-      case tList1:
-      case tList2:
-      case tListN:
-        if (seen.find(v.listElems()) == seen.end()) {
-          seen.insert(v.listElems());
+      case tList:
+        if (seen.find(v.list) == seen.end()) {
+          seen.insert(v.list);
           sz += v.listSize() * sizeof(Value*);
           for (size_t n = 0; n < v.listSize(); ++n) {
-            sz += doValue(*v.listElems()[n]);
+            sz += doValue(*(*v.list)[n]);
           }
         }
         break;
diff --git a/third_party/nix/src/libexpr/eval.hh b/third_party/nix/src/libexpr/eval.hh
index 3da0961b6f4a..3e875fa81134 100644
--- a/third_party/nix/src/libexpr/eval.hh
+++ b/third_party/nix/src/libexpr/eval.hh
@@ -260,12 +260,19 @@ class EvalState {
 
   Value* allocAttr(Value& vAttrs, const Symbol& name);
 
-  void mkList(Value& v, size_t size);
+  // Create a list value from the specified vector.
+  void mkList(Value& v, NixList* list);
+
+  // Create a list value, allocating as many elements as specified in
+  // size. This is used for the many cases in this codebase where
+  // assignment happens into the preallocated list.
+  void mkList(Value& v, size_t size = 0);
+
   void mkAttrs(Value& v, size_t capacity);
   void mkThunk_(Value& v, Expr* expr);
   void mkPos(Value& v, Pos* pos);
 
-  void concatLists(Value& v, size_t nrLists, Value** lists, const Pos& pos);
+  void concatLists(Value& v, const NixList& lists, const Pos& pos);
 
   /* Print statistics. */
   void printStats();
diff --git a/third_party/nix/src/libexpr/get-drvs.cc b/third_party/nix/src/libexpr/get-drvs.cc
index 33bded2fa265..1d8fe1efa073 100644
--- a/third_party/nix/src/libexpr/get-drvs.cc
+++ b/third_party/nix/src/libexpr/get-drvs.cc
@@ -99,8 +99,8 @@ DrvInfo::Outputs DrvInfo::queryOutputs(bool onlyOutputsToInstall) {
       /* For each output... */
       for (unsigned int j = 0; j < i->second.value->listSize(); ++j) {
         /* Evaluate the corresponding set. */
-        std::string name = state->forceStringNoCtx(
-            *i->second.value->listElems()[j], *i->second.pos);
+        std::string name = state->forceStringNoCtx(*(*i->second.value->list)[j],
+                                                   *i->second.pos);
         Bindings::iterator out = attrs->find(state->symbols.Create(name));
         if (out == attrs->end()) {
           continue;  // FIXME: throw error?
@@ -136,12 +136,12 @@ DrvInfo::Outputs DrvInfo::queryOutputs(bool onlyOutputsToInstall) {
     throw errMsg;
   }
   Outputs result;
-  for (auto i = outTI->listElems(); i != outTI->listElems() + outTI->listSize();
-       ++i) {
-    if ((*i)->type != tString) {
+
+  for (Value* i : *outTI->list) {
+    if (i->type != tString) {
       throw errMsg;
     }
-    auto out = outputs.find((*i)->string.s);
+    auto out = outputs.find(i->string.s);
     if (out == outputs.end()) {
       throw errMsg;
     }
@@ -190,7 +190,7 @@ bool DrvInfo::checkMeta(Value& v) {
   state->forceValue(v);
   if (v.isList()) {
     for (unsigned int n = 0; n < v.listSize(); ++n) {
-      if (!checkMeta(*v.listElems()[n])) {
+      if (!checkMeta(*(*v.list)[n])) {
         return false;
       }
     }
@@ -418,10 +418,10 @@ static void getDerivations(EvalState& state, Value& vIn,
     for (unsigned int n = 0; n < v.listSize(); ++n) {
       std::string pathPrefix2 =
           addToPath(pathPrefix, (format("%1%") % n).str());
-      if (getDerivation(state, *v.listElems()[n], pathPrefix2, drvs, done,
+      if (getDerivation(state, *(*v.list)[n], pathPrefix2, drvs, done,
                         ignoreAssertionFailures)) {
-        getDerivations(state, *v.listElems()[n], pathPrefix2, autoArgs, drvs,
-                       done, ignoreAssertionFailures);
+        getDerivations(state, *(*v.list)[n], pathPrefix2, autoArgs, drvs, done,
+                       ignoreAssertionFailures);
       }
     }
   }
diff --git a/third_party/nix/src/libexpr/json-to-value.cc b/third_party/nix/src/libexpr/json-to-value.cc
index 4411b411f229..5f8352dde63b 100644
--- a/third_party/nix/src/libexpr/json-to-value.cc
+++ b/third_party/nix/src/libexpr/json-to-value.cc
@@ -63,7 +63,7 @@ static void parseJSON(EvalState& state, const char*& s, Value& v) {
 
   if (*s == '[') {
     s++;
-    ValueVector values;
+    NixList values;
     values.reserve(128);
     skipWhitespace(s);
     while (true) {
@@ -85,7 +85,7 @@ static void parseJSON(EvalState& state, const char*& s, Value& v) {
     s++;
     state.mkList(v, values.size());
     for (size_t n = 0; n < values.size(); ++n) {
-      v.listElems()[n] = values[n];
+      (*v.list)[n] = values[n];
     }
   }
 
diff --git a/third_party/nix/src/libexpr/primops.cc b/third_party/nix/src/libexpr/primops.cc
index 6b3eaa4c0898..9cda2a1472c9 100644
--- a/third_party/nix/src/libexpr/primops.cc
+++ b/third_party/nix/src/libexpr/primops.cc
@@ -127,9 +127,10 @@ static void prim_scopedImport(EvalState& state, const Pos& pos, Value** args,
     for (const auto& o : drv.outputs) {
       v2 = state.allocAttr(w, state.symbols.Create(o.first));
       mkString(*v2, o.second.path, {"!" + o.first + "!" + path});
-      outputsVal->listElems()[outputs_index] = state.allocValue();
-      mkString(*(outputsVal->listElems()[outputs_index++]), o.first);
+      (*outputsVal->list)[outputs_index] = state.allocValue();
+      mkString(*((*outputsVal->list)[outputs_index++]), o.first);
     }
+
     Value fun;
     state.evalFile(
         settings.nixDataDir + "/nix/corepkgs/imported-drv-to-derivation.nix",
@@ -231,9 +232,7 @@ static void prim_typeOf(EvalState& state, const Pos& pos, Value** args,
     case tAttrs:
       t = "set";
       break;
-    case tList1:
-    case tList2:
-    case tListN:
+    case tList:
       t = "list";
       break;
     case tLambda:
@@ -360,8 +359,8 @@ static void prim_genericClosure(EvalState& state, const Pos& pos, Value** args,
   state.forceList(*startSet->second.value, pos);
 
   ValueList workSet;
-  for (unsigned int n = 0; n < startSet->second.value->listSize(); ++n) {
-    workSet.push_back(startSet->second.value->listElems()[n]);
+  for (Value* elem : *startSet->second.value->list) {
+    workSet.push_back(elem);
   }
 
   /* Get the operator. */
@@ -404,8 +403,8 @@ static void prim_genericClosure(EvalState& state, const Pos& pos, Value** args,
 
     /* Add the values returned by the operator to the work set. */
     for (unsigned int n = 0; n < call.listSize(); ++n) {
-      state.forceValue(*call.listElems()[n]);
-      workSet.push_back(call.listElems()[n]);
+      state.forceValue(*(*call.list)[n]);
+      workSet.push_back((*call.list)[n]);
     }
   }
 
@@ -413,7 +412,7 @@ static void prim_genericClosure(EvalState& state, const Pos& pos, Value** args,
   state.mkList(v, res.size());
   unsigned int n = 0;
   for (auto& i : res) {
-    v.listElems()[n++] = i;
+    (*v.list)[n++] = i;
   }
 }
 
@@ -620,7 +619,7 @@ static void prim_derivationStrict(EvalState& state, const Pos& pos,
         state.forceList(*i->value, pos);
         for (unsigned int n = 0; n < i->value->listSize(); ++n) {
           std::string s = state.coerceToString(
-              posDrvName, *i->value->listElems()[n], context, true);
+              posDrvName, *(*i->value->list)[n], context, true);
           drv.args.push_back(s);
         }
       }
@@ -651,8 +650,8 @@ static void prim_derivationStrict(EvalState& state, const Pos& pos,
             state.forceList(*i->value, posDrvName);
             Strings ss;
             for (unsigned int n = 0; n < i->value->listSize(); ++n) {
-              ss.emplace_back(state.forceStringNoCtx(*i->value->listElems()[n],
-                                                     posDrvName));
+              ss.emplace_back(
+                  state.forceStringNoCtx(*(*i->value->list)[n], posDrvName));
             }
             handleOutputs(ss);
           }
@@ -942,7 +941,7 @@ static void prim_findFile(EvalState& state, const Pos& pos, Value** args,
   SearchPath searchPath;
 
   for (unsigned int n = 0; n < args[0]->listSize(); ++n) {
-    Value& v2(*args[0]->listElems()[n]);
+    Value& v2(*(*args[0]->list)[n]);
     state.forceAttrs(v2, pos);
 
     std::string prefix;
@@ -1225,7 +1224,7 @@ static void prim_attrNames(EvalState& state, const Pos& pos, Value** args,
 
   unsigned int n = 0;
   for (auto& [key, value] : *args[0]->attrs) {
-    mkString(*(v.listElems()[n++] = state.allocValue()), key);
+    mkString(*((*v.list)[n++] = state.allocValue()), key);
   }
 }
 
@@ -1239,7 +1238,7 @@ static void prim_attrValues(EvalState& state, const Pos& pos, Value** input,
 
   unsigned int n = 0;
   for (auto& [key, value] : *input[0]->attrs) {
-    output.listElems()[n++] = value.value;
+    (*output.list)[n++] = value.value;
   }
 }
 
@@ -1297,8 +1296,8 @@ static void prim_removeAttrs(EvalState& state, const Pos& pos, Value** args,
   /* Get the attribute names to be removed. */
   std::set<Symbol> names;
   for (unsigned int i = 0; i < args[1]->listSize(); ++i) {
-    state.forceStringNoCtx(*args[1]->listElems()[i], pos);
-    names.insert(state.symbols.Create(args[1]->listElems()[i]->string.s));
+    state.forceStringNoCtx(*(*args[1]->list)[i], pos);
+    names.insert(state.symbols.Create((*args[1]->list)[i]->string.s));
   }
 
   /* Copy all attributes not in that set.  Note that we don't need
@@ -1326,7 +1325,7 @@ static void prim_listToAttrs(EvalState& state, const Pos& pos, Value** args,
   std::set<Symbol> seen;
 
   for (unsigned int i = 0; i < args[0]->listSize(); ++i) {
-    Value& v2(*args[0]->listElems()[i]);
+    Value& v2(*(*args[0]->list)[i]);
     state.forceAttrs(v2, pos);
 
     Bindings::iterator j = v2.attrs->find(state.sName);
@@ -1391,7 +1390,7 @@ static void prim_catAttrs(EvalState& state, const Pos& pos, Value** args,
   unsigned int found = 0;
 
   for (unsigned int n = 0; n < args[1]->listSize(); ++n) {
-    Value& v2(*args[1]->listElems()[n]);
+    Value& v2(*(*args[1]->list)[n]);
     state.forceAttrs(v2, pos);
     Bindings::iterator i = v2.attrs->find(attrName);
     if (i != v2.attrs->end()) {
@@ -1401,7 +1400,7 @@ static void prim_catAttrs(EvalState& state, const Pos& pos, Value** args,
 
   state.mkList(v, found);
   for (unsigned int n = 0; n < found; ++n) {
-    v.listElems()[n] = res[n];
+    (*v.list)[n] = res[n];
   }
 }
 
@@ -1472,8 +1471,8 @@ static void elemAt(EvalState& state, const Pos& pos, Value& list, int n,
   if (n < 0 || (unsigned int)n >= list.listSize()) {
     throw Error(format("list index %1% is out of bounds, at %2%") % n % pos);
   }
-  state.forceValue(*list.listElems()[n]);
-  v = *list.listElems()[n];
+  state.forceValue(*(*list.list)[n]);
+  v = *(*list.list)[n];
 }
 
 /* Return the n-1'th element of a list. */
@@ -1499,7 +1498,7 @@ static void prim_tail(EvalState& state, const Pos& pos, Value** args,
   }
   state.mkList(v, args[0]->listSize() - 1);
   for (unsigned int n = 0; n < v.listSize(); ++n) {
-    v.listElems()[n] = args[0]->listElems()[n + 1];
+    (*v.list)[n] = (*args[0]->list)[n + 1];
   }
 }
 
@@ -1510,8 +1509,7 @@ static void prim_map(EvalState& state, const Pos& pos, Value** args, Value& v) {
   state.mkList(v, args[1]->listSize());
 
   for (unsigned int n = 0; n < v.listSize(); ++n) {
-    mkApp(*(v.listElems()[n] = state.allocValue()), *args[0],
-          *args[1]->listElems()[n]);
+    mkApp(*((*v.list)[n] = state.allocValue()), *args[0], *(*args[1]->list)[n]);
   }
 }
 
@@ -1530,9 +1528,9 @@ static void prim_filter(EvalState& state, const Pos& pos, Value** args,
   bool same = true;
   for (unsigned int n = 0; n < args[1]->listSize(); ++n) {
     Value res;
-    state.callFunction(*args[0], *args[1]->listElems()[n], res, noPos);
+    state.callFunction(*args[0], *(*args[1]->list)[n], res, noPos);
     if (state.forceBool(res, pos)) {
-      vs[k++] = args[1]->listElems()[n];
+      vs[k++] = (*args[1]->list)[n];
     } else {
       same = false;
     }
@@ -1543,7 +1541,7 @@ static void prim_filter(EvalState& state, const Pos& pos, Value** args,
   } else {
     state.mkList(v, k);
     for (unsigned int n = 0; n < k; ++n) {
-      v.listElems()[n] = vs[n];
+      (*v.list)[n] = vs[n];
     }
   }
 }
@@ -1554,7 +1552,7 @@ static void prim_elem(EvalState& state, const Pos& pos, Value** args,
   bool res = false;
   state.forceList(*args[1], pos);
   for (unsigned int n = 0; n < args[1]->listSize(); ++n) {
-    if (state.eqValues(*args[0], *args[1]->listElems()[n])) {
+    if (state.eqValues(*args[0], *(*args[1]->list)[n])) {
       res = true;
       break;
     }
@@ -1566,7 +1564,7 @@ static void prim_elem(EvalState& state, const Pos& pos, Value** args,
 static void prim_concatLists(EvalState& state, const Pos& pos, Value** args,
                              Value& v) {
   state.forceList(*args[0], pos);
-  state.concatLists(v, args[0]->listSize(), args[0]->listElems(), pos);
+  state.concatLists(v, *args[0]->list, pos);
 }
 
 /* Return the length of a list.  This is an O(1) time operation. */
@@ -1590,7 +1588,7 @@ static void prim_foldlStrict(EvalState& state, const Pos& pos, Value** args,
       Value vTmp;
       state.callFunction(*args[0], *vCur, vTmp, pos);
       vCur = n == args[2]->listSize() - 1 ? &v : state.allocValue();
-      state.callFunction(vTmp, *args[2]->listElems()[n], *vCur, pos);
+      state.callFunction(vTmp, *(*args[2]->list)[n], *vCur, pos);
     }
     state.forceValue(v);
   } else {
@@ -1606,7 +1604,7 @@ static void anyOrAll(bool any, EvalState& state, const Pos& pos, Value** args,
 
   Value vTmp;
   for (unsigned int n = 0; n < args[1]->listSize(); ++n) {
-    state.callFunction(*args[0], *args[1]->listElems()[n], vTmp, pos);
+    state.callFunction(*args[0], *(*args[1]->list)[n], vTmp, pos);
     bool res = state.forceBool(vTmp, pos);
     if (res == any) {
       mkBool(v, any);
@@ -1639,7 +1637,7 @@ static void prim_genList(EvalState& state, const Pos& pos, Value** args,
   for (unsigned int n = 0; n < (unsigned int)len; ++n) {
     Value* arg = state.allocValue();
     mkInt(*arg, n);
-    mkApp(*(v.listElems()[n] = state.allocValue()), *args[0], *arg);
+    mkApp(*((*v.list)[n] = state.allocValue()), *args[0], *arg);
   }
 }
 
@@ -1651,12 +1649,11 @@ static void prim_sort(EvalState& state, const Pos& pos, Value** args,
   state.forceFunction(*args[0], pos);
   state.forceList(*args[1], pos);
 
-  auto len = args[1]->listSize();
-  state.mkList(v, len);
-  for (unsigned int n = 0; n < len; ++n) {
-    state.forceValue(*args[1]->listElems()[n]);
-    v.listElems()[n] = args[1]->listElems()[n];
-  }
+  // Copy of the input list which can be sorted in place.
+  auto outlist = new (GC) NixList(*args[1]->list);
+
+  std::for_each(outlist->begin(), outlist->end(),
+                [&](Value* val) { state.forceValue(*val); });
 
   auto comparator = [&](Value* a, Value* b) {
     /* Optimization: if the comparator is lessThan, bypass
@@ -1675,7 +1672,7 @@ static void prim_sort(EvalState& state, const Pos& pos, Value** args,
   /* FIXME: std::sort can segfault if the comparator is not a strict
      weak ordering. What to do? std::stable_sort() seems more
      resilient, but no guarantees... */
-  std::stable_sort(v.listElems(), v.listElems() + len, comparator);
+  std::stable_sort(v.list->begin(), v.list->end(), comparator);
 }
 
 static void prim_partition(EvalState& state, const Pos& pos, Value** args,
@@ -1685,36 +1682,28 @@ static void prim_partition(EvalState& state, const Pos& pos, Value** args,
 
   auto len = args[1]->listSize();
 
-  ValueVector right;
-  ValueVector wrong;
+  NixList* right = new (GC) NixList();
+  NixList* wrong = new (GC) NixList();
+
+  for (Value* elem : *args[1]->list) {
+    state.forceValue(*elem, pos);
 
-  for (unsigned int n = 0; n < len; ++n) {
-    auto vElem = args[1]->listElems()[n];
-    state.forceValue(*vElem);
     Value res;
-    state.callFunction(*args[0], *vElem, res, pos);
+    state.callFunction(*args[0], *elem, res, pos);
     if (state.forceBool(res, pos)) {
-      right.push_back(vElem);
+      right->push_back(elem);
     } else {
-      wrong.push_back(vElem);
+      wrong->push_back(elem);
     }
   }
 
   state.mkAttrs(v, 2);
 
   Value* vRight = state.allocAttr(v, state.sRight);
-  auto rsize = right.size();
-  state.mkList(*vRight, rsize);
-  if (rsize != 0u) {
-    memcpy(vRight->listElems(), right.data(), sizeof(Value*) * rsize);
-  }
+  state.mkList(*vRight, right);
 
   Value* vWrong = state.allocAttr(v, state.sWrong);
-  auto wsize = wrong.size();
-  state.mkList(*vWrong, wsize);
-  if (wsize != 0u) {
-    memcpy(vWrong->listElems(), wrong.data(), sizeof(Value*) * wsize);
-  }
+  state.mkList(*vWrong, wrong);
 }
 
 /* concatMap = f: list: concatLists (map f list); */
@@ -1723,27 +1712,18 @@ static void prim_concatMap(EvalState& state, const Pos& pos, Value** args,
                            Value& v) {
   state.forceFunction(*args[0], pos);
   state.forceList(*args[1], pos);
-  auto nrLists = args[1]->listSize();
 
-  Value lists[nrLists];
-  size_t len = 0;
+  NixList* outlist = new (GC) NixList;
 
-  for (unsigned int n = 0; n < nrLists; ++n) {
-    Value* vElem = args[1]->listElems()[n];
-    state.callFunction(*args[0], *vElem, lists[n], pos);
-    state.forceList(lists[n], pos);
-    len += lists[n].listSize();
-  }
+  for (Value* elem : *args[1]->list) {
+    auto out = state.allocValue();
+    state.callFunction(*args[0], *elem, *out, pos);
+    state.forceList(*out, pos);
 
-  state.mkList(v, len);
-  auto out = v.listElems();
-  for (unsigned int n = 0, pos = 0; n < nrLists; ++n) {
-    auto l = lists[n].listSize();
-    if (l != 0u) {
-      memcpy(out + pos, lists[n].listElems(), l * sizeof(Value*));
-    }
-    pos += l;
+    outlist->insert(outlist->end(), out->list->begin(), out->list->end());
   }
+
+  state.mkList(v, outlist);
 }
 
 /*************************************************************
@@ -1908,9 +1888,9 @@ static void prim_match(EvalState& state, const Pos& pos, Value** args,
     state.mkList(v, len);
     for (size_t i = 0; i < len; ++i) {
       if (!match[i + 1].matched) {
-        mkNull(*(v.listElems()[i] = state.allocValue()));
+        mkNull(*((*v.list)[i] = state.allocValue()));
       } else {
-        mkString(*(v.listElems()[i] = state.allocValue()),
+        mkString(*((*v.list)[i] = state.allocValue()),
                  match[i + 1].str().c_str());
       }
     }
@@ -1947,7 +1927,7 @@ static void prim_split(EvalState& state, const Pos& pos, Value** args,
     Value* elem;
 
     if (len == 0) {
-      v.listElems()[idx++] = args[1];
+      (*v.list)[idx++] = args[1];
       return;
     }
 
@@ -1956,27 +1936,27 @@ static void prim_split(EvalState& state, const Pos& pos, Value** args,
       std::smatch match = *i;
 
       // Add a string for non-matched characters.
-      elem = v.listElems()[idx++] = state.allocValue();
+      elem = (*v.list)[idx++] = state.allocValue();
       mkString(*elem, match.prefix().str().c_str());
 
       // Add a list for matched substrings.
       const size_t slen = match.size() - 1;
-      elem = v.listElems()[idx++] = state.allocValue();
+      elem = (*v.list)[idx++] = state.allocValue();
 
       // Start at 1, beacause the first match is the whole string.
       state.mkList(*elem, slen);
       for (size_t si = 0; si < slen; ++si) {
         if (!match[si + 1].matched) {
-          mkNull(*(elem->listElems()[si] = state.allocValue()));
+          mkNull(*((*elem->list)[si] = state.allocValue()));
         } else {
-          mkString(*(elem->listElems()[si] = state.allocValue()),
+          mkString(*((*elem->list)[si] = state.allocValue()),
                    match[si + 1].str().c_str());
         }
       }
 
       // Add a string for non-matched suffix characters.
       if (idx == 2 * len) {
-        elem = v.listElems()[idx++] = state.allocValue();
+        elem = (*v.list)[idx++] = state.allocValue();
         mkString(*elem, match.suffix().str().c_str());
       }
     }
@@ -2010,7 +1990,7 @@ static void prim_concatStringSep(EvalState& state, const Pos& pos, Value** args,
       res += sep;
     }
 
-    res += state.coerceToString(pos, *args[1]->listElems()[n], context);
+    res += state.coerceToString(pos, *(*args[1]->list)[n], context);
   }
 
   mkString(v, res, context);
@@ -2029,14 +2009,14 @@ static void prim_replaceStrings(EvalState& state, const Pos& pos, Value** args,
   std::vector<std::string> from;
   from.reserve(args[0]->listSize());
   for (unsigned int n = 0; n < args[0]->listSize(); ++n) {
-    from.push_back(state.forceString(*args[0]->listElems()[n], pos));
+    from.push_back(state.forceString(*(*args[0]->list)[n], pos));
   }
 
   std::vector<std::pair<std::string, PathSet>> to;
   to.reserve(args[1]->listSize());
   for (unsigned int n = 0; n < args[1]->listSize(); ++n) {
     PathSet ctx;
-    auto s = state.forceString(*args[1]->listElems()[n], ctx, pos);
+    auto s = state.forceString(*(*args[1]->list)[n], ctx, pos);
     to.emplace_back(std::move(s), std::move(ctx));
   }
 
@@ -2116,7 +2096,7 @@ static void prim_splitVersion(EvalState& state, const Pos& pos, Value** args,
   state.mkList(v, components.size());
   unsigned int n = 0;
   for (auto& component : components) {
-    auto listElem = v.listElems()[n++] = state.allocValue();
+    auto listElem = (*v.list)[n++] = state.allocValue();
     mkString(*listElem, component);
   }
 }
@@ -2386,7 +2366,7 @@ void EvalState::createBaseEnv() {
   mkList(v, searchPath.size());
   int n = 0;
   for (auto& i : searchPath) {
-    v2 = v.listElems()[n++] = allocValue();
+    v2 = (*v.list)[n++] = allocValue();
     mkAttrs(*v2, 2);
     mkString(*allocAttr(*v2, symbols.Create("path")), i.second);
     mkString(*allocAttr(*v2, symbols.Create("prefix")), i.first);
diff --git a/third_party/nix/src/libexpr/primops/context.cc b/third_party/nix/src/libexpr/primops/context.cc
index 3a39e03eabc7..841a45c61c03 100644
--- a/third_party/nix/src/libexpr/primops/context.cc
+++ b/third_party/nix/src/libexpr/primops/context.cc
@@ -123,7 +123,7 @@ static void prim_getContext(EvalState& state, const Pos& pos, Value** args,
       state.mkList(outputsVal, info.second.outputs.size());
       size_t i = 0;
       for (const auto& output : info.second.outputs) {
-        mkString(*(outputsVal.listElems()[i++] = state.allocValue()), output);
+        mkString(*((*outputsVal.list)[i++] = state.allocValue()), output);
       }
     }
   }
@@ -184,7 +184,7 @@ static void prim_appendContext(EvalState& state, const Pos& pos, Value** args,
             i->name, i->pos);
       }
       for (unsigned int n = 0; n < iter->second.value->listSize(); ++n) {
-        auto name = state.forceStringNoCtx(*iter->second.value->listElems()[n],
+        auto name = state.forceStringNoCtx(*(*iter->second.value->list)[n],
                                            *iter->second.pos);
         context.insert("!" + name + "!" + std::string(i->name));
       }
diff --git a/third_party/nix/src/libexpr/primops/fromTOML.cc b/third_party/nix/src/libexpr/primops/fromTOML.cc
index 66e2e1b4094f..389ac080677a 100644
--- a/third_party/nix/src/libexpr/primops/fromTOML.cc
+++ b/third_party/nix/src/libexpr/primops/fromTOML.cc
@@ -31,7 +31,7 @@ static void prim_fromTOML(EvalState& state, const Pos& pos, Value** args,
           size_t size2 = i2->get().size();
           state.mkList(v2, size2);
           for (size_t j = 0; j < size2; ++j)
-            visit(*(v2.listElems()[j] = state.allocValue()), i2->get()[j]);
+            visit(*((*v2.list)[j] = state.allocValue()), i2->get()[j]);
         } else
           visit(v2, i.second);
       }
@@ -43,7 +43,7 @@ static void prim_fromTOML(EvalState& state, const Pos& pos, Value** args,
       state.mkList(v, size);
 
       for (size_t i = 0; i < size; ++i)
-        visit(*(v.listElems()[i] = state.allocValue()), t2->get()[i]);
+        visit(*((*v.list)[i] = state.allocValue()), t2->get()[i]);
     }
 
     // Handle cases like 'a = [[{ a = true }]]', which IMHO should be
@@ -56,7 +56,7 @@ static void prim_fromTOML(EvalState& state, const Pos& pos, Value** args,
       state.mkList(v, size);
 
       for (size_t j = 0; j < size; ++j)
-        visit(*(v.listElems()[j] = state.allocValue()), t2->get()[j]);
+        visit(*((*v.list)[j] = state.allocValue()), t2->get()[j]);
     }
 
     else if (t->is_value()) {
diff --git a/third_party/nix/src/libexpr/value-to-json.cc b/third_party/nix/src/libexpr/value-to-json.cc
index a51a1cee3043..3e5e025a27be 100644
--- a/third_party/nix/src/libexpr/value-to-json.cc
+++ b/third_party/nix/src/libexpr/value-to-json.cc
@@ -64,14 +64,11 @@ void printValueAsJSON(EvalState& state, bool strict, Value& v,
       break;
     }
 
-    case tList1:
-    case tList2:
-    case tListN: {
+    case tList: {
       auto list(out.list());
       for (unsigned int n = 0; n < v.listSize(); ++n) {
         auto placeholder(list.placeholder());
-        printValueAsJSON(state, strict, *v.listElems()[n], placeholder,
-                         context);
+        printValueAsJSON(state, strict, *(*v.list)[n], placeholder, context);
       }
       break;
     }
diff --git a/third_party/nix/src/libexpr/value-to-xml.cc b/third_party/nix/src/libexpr/value-to-xml.cc
index ea1a85a89719..aba6013f9891 100644
--- a/third_party/nix/src/libexpr/value-to-xml.cc
+++ b/third_party/nix/src/libexpr/value-to-xml.cc
@@ -127,13 +127,11 @@ static void printValueAsXML(EvalState& state, bool strict, bool location,
 
       break;
 
-    case tList1:
-    case tList2:
-    case tListN: {
+    case tList: {
       XMLOpenElement _(doc, "list");
       for (unsigned int n = 0; n < v.listSize(); ++n) {
-        printValueAsXML(state, strict, location, *v.listElems()[n], doc,
-                        context, drvsSeen);
+        printValueAsXML(state, strict, location, *(*v.list)[n], doc, context,
+                        drvsSeen);
       }
       break;
     }
diff --git a/third_party/nix/src/libexpr/value.hh b/third_party/nix/src/libexpr/value.hh
index cb1b8796cfe4..35c5e4d0a0b5 100644
--- a/third_party/nix/src/libexpr/value.hh
+++ b/third_party/nix/src/libexpr/value.hh
@@ -1,6 +1,10 @@
 #pragma once
 
+#include <tuple>
+#include <vector>
+
 #include <gc/gc_allocator.h>
+#include <gc/gc_cpp.h>
 
 #include "libexpr/symbol-table.hh"
 #include "libutil/types.hh"
@@ -14,9 +18,7 @@ typedef enum {
   tPath,
   tNull,
   tAttrs,
-  tList1,
-  tList2,
-  tListN,
+  tList,
   tThunk,
   tApp,
   tLambda,
@@ -119,11 +121,6 @@ struct NixString {
   const char** context;  // must be in sorted order
 };
 
-struct NixBigList {
-  size_t size;
-  Value** elems;
-};
-
 struct NixThunk {
   Env* env;
   Expr* expr;
@@ -142,7 +139,9 @@ struct NixPrimOpApp {
   Value *left, *right;
 };
 
-struct Value {
+using NixList = std::vector<Value*, traceable_allocator<Value*>>;
+
+struct Value : public gc {
   ValueType type;
   union {  // TODO(tazjin): std::variant
     NixInt integer;
@@ -150,8 +149,7 @@ struct Value {
     NixString string;
     const char* path;
     Bindings* attrs;
-    NixBigList bigList;
-    Value* smallList[2];
+    NixList* list;
     NixThunk thunk;
     NixApp app;  // TODO(tazjin): "app"?
     NixLambda lambda;
@@ -161,21 +159,9 @@ struct Value {
     NixFloat fpoint;
   };
 
-  bool isList() const {
-    return type == tList1 || type == tList2 || type == tListN;
-  }
-
-  Value** listElems() {
-    return type == tList1 || type == tList2 ? smallList : bigList.elems;
-  }
-
-  const Value* const* listElems() const {
-    return type == tList1 || type == tList2 ? smallList : bigList.elems;
-  }
+  bool isList() const { return type == tList; }
 
-  size_t listSize() const {
-    return type == tList1 ? 1 : type == tList2 ? 2 : bigList.size;
-  }
+  size_t listSize() const { return list->size(); }
 };
 
 /* After overwriting an app node, be sure to clear pointers in the
@@ -242,7 +228,6 @@ void mkPath(Value& v, const char* s);
    not included. */
 size_t valueSize(Value& v);
 
-typedef std::vector<Value*, traceable_allocator<Value*>> ValueVector;
 typedef std::map<Symbol, Value*, std::less<Symbol>,
                  traceable_allocator<std::pair<const Symbol, Value*>>>
     ValueMap;
diff --git a/third_party/nix/src/libstore/worker-protocol.hh b/third_party/nix/src/libstore/worker-protocol.hh
index 663b1ff08154..e2f40a449d86 100644
--- a/third_party/nix/src/libstore/worker-protocol.hh
+++ b/third_party/nix/src/libstore/worker-protocol.hh
@@ -33,8 +33,8 @@ typedef enum {
   wopQuerySubstitutablePathInfo = 21,
   wopQueryDerivationOutputs = 22,
   wopQueryAllValidPaths = 23,
-  wopQueryFailedPaths = 24, // obsolete
-  wopClearFailedPaths = 25, // obsolete
+  wopQueryFailedPaths = 24,  // obsolete
+  wopClearFailedPaths = 25,  // obsolete
   wopQueryPathInfo = 26,
   wopImportPaths = 27,  // obsolete
   wopQueryDerivationOutputNames = 28,
diff --git a/third_party/nix/src/nix-env/nix-env.cc b/third_party/nix/src/nix-env/nix-env.cc
index 10e2e9492e6c..07bcb54eb6f2 100644
--- a/third_party/nix/src/nix-env/nix-env.cc
+++ b/third_party/nix/src/nix-env/nix-env.cc
@@ -158,8 +158,7 @@ static void loadSourceExpr(EvalState& state, const Path& path, Value& v) {
      directory). */
   else if (S_ISDIR(st.st_mode)) {
     state.mkAttrs(v, 1024);
-    state.mkList(*state.allocAttr(v, state.symbols.Create("_combineChannels")),
-                 0);
+    state.mkList(*state.allocAttr(v, state.symbols.Create("_combineChannels")));
     StringSet attrs;
     getAllExprs(state, path, attrs, v);
   }
@@ -1199,11 +1198,11 @@ static void opQuery(Globals& globals, Strings opFlags, Strings opArgs) {
                   attrs2["type"] = "strings";
                   XMLOpenElement m(xml, "meta", attrs2);
                   for (unsigned int j = 0; j < v->listSize(); ++j) {
-                    if (v->listElems()[j]->type != tString) {
+                    if ((*v->list)[j]->type != tString) {
                       continue;
                     }
                     XMLAttrs attrs3;
-                    attrs3["value"] = v->listElems()[j]->string.s;
+                    attrs3["value"] = (*v->list)[j]->string.s;
                     xml.writeEmptyElement("string", attrs3);
                   }
                 } else if (v->type == tAttrs) {
diff --git a/third_party/nix/src/nix-env/user-env.cc b/third_party/nix/src/nix-env/user-env.cc
index 8130eafbdf35..06329e74f340 100644
--- a/third_party/nix/src/nix-env/user-env.cc
+++ b/third_party/nix/src/nix-env/user-env.cc
@@ -51,29 +51,29 @@ bool createUserEnv(EvalState& state, DrvInfos& elems, const Path& profile,
        as the meta attributes. */
     Path drvPath = keepDerivations ? i.queryDrvPath() : "";
 
-    Value& v(*state.allocValue());
-    manifest.listElems()[n++] = &v;
-    state.mkAttrs(v, 16);
+    Value* v = state.allocValue();
+    (*manifest.list)[n++] = v;
+    state.mkAttrs(*v, 16);
 
-    mkString(*state.allocAttr(v, state.sType), "derivation");
-    mkString(*state.allocAttr(v, state.sName), i.queryName());
+    mkString(*state.allocAttr(*v, state.sType), "derivation");
+    mkString(*state.allocAttr(*v, state.sName), i.queryName());
     auto system = i.querySystem();
     if (!system.empty()) {
-      mkString(*state.allocAttr(v, state.sSystem), system);
+      mkString(*state.allocAttr(*v, state.sSystem), system);
     }
-    mkString(*state.allocAttr(v, state.sOutPath), i.queryOutPath());
+    mkString(*state.allocAttr(*v, state.sOutPath), i.queryOutPath());
     if (!drvPath.empty()) {
-      mkString(*state.allocAttr(v, state.sDrvPath), i.queryDrvPath());
+      mkString(*state.allocAttr(*v, state.sDrvPath), i.queryDrvPath());
     }
 
     // Copy each output meant for installation.
     DrvInfo::Outputs outputs = i.queryOutputs(true);
-    Value& vOutputs = *state.allocAttr(v, state.sOutputs);
+    Value& vOutputs = *state.allocAttr(*v, state.sOutputs);
     state.mkList(vOutputs, outputs.size());
     unsigned int m = 0;
     for (auto& j : outputs) {
-      mkString(*(vOutputs.listElems()[m++] = state.allocValue()), j.first);
-      Value& vOutputs = *state.allocAttr(v, state.symbols.Create(j.first));
+      mkString(*((*vOutputs.list)[m++] = state.allocValue()), j.first);
+      Value& vOutputs = *state.allocAttr(*v, state.symbols.Create(j.first));
       state.mkAttrs(vOutputs, 2);
       mkString(*state.allocAttr(vOutputs, state.sOutPath), j.second);
 
@@ -86,7 +86,7 @@ bool createUserEnv(EvalState& state, DrvInfos& elems, const Path& profile,
     }
 
     // Copy the meta attributes.
-    Value& vMeta = *state.allocAttr(v, state.sMeta);
+    Value& vMeta = *state.allocAttr(*v, state.sMeta);
     state.mkAttrs(vMeta, 16);
     StringSet metaNames = i.queryMetaNames();
     for (auto& j : metaNames) {
diff --git a/third_party/nix/src/nix-prefetch-url/nix-prefetch-url.cc b/third_party/nix/src/nix-prefetch-url/nix-prefetch-url.cc
index a83ac62635be..b9de2e826b8e 100644
--- a/third_party/nix/src/nix-prefetch-url/nix-prefetch-url.cc
+++ b/third_party/nix/src/nix-prefetch-url/nix-prefetch-url.cc
@@ -50,8 +50,7 @@ std::string resolveMirrorUri(EvalState& state, std::string uri) {
     throw Error(format("mirror URI '%1%' did not expand to anything") % uri);
   }
 
-  std::string mirror =
-      state.forceString(*mirrorList->second.value->listElems()[0]);
+  std::string mirror = state.forceString(*(*mirrorList->second.value->list)[0]);
   return mirror + (absl::EndsWith(mirror, "/") ? "" : "/") +
          std::string(s, p + 1);
 }
@@ -137,7 +136,7 @@ static int _main(int argc, char** argv) {
       if (attr->second.value->listSize() < 1) {
         throw Error("'urls' list is empty");
       }
-      uri = state->forceString(*attr->second.value->listElems()[0]);
+      uri = state->forceString(*(*attr->second.value->list)[0]);
 
       /* Extract the hash mode. */
       attr = v.attrs->find(state->symbols.Create("outputHashMode"));
diff --git a/third_party/nix/src/nix/repl.cc b/third_party/nix/src/nix/repl.cc
index 823bb3b88ca5..b8edfc0e1c04 100644
--- a/third_party/nix/src/nix/repl.cc
+++ b/third_party/nix/src/nix/repl.cc
@@ -748,19 +748,17 @@ std::ostream& NixRepl::printValue(std::ostream& str, Value& v,
       break;
     }
 
-    case tList1:
-    case tList2:
-    case tListN:
+    case tList:
       seen.insert(&v);
 
       str << "[ ";
       if (maxDepth > 0) {
         for (unsigned int n = 0; n < v.listSize(); ++n) {
-          if (seen.find(v.listElems()[n]) != seen.end()) {
+          if (seen.find((*v.list)[n]) != seen.end()) {
             str << "«repeated»";
           } else {
             try {
-              printValue(str, *v.listElems()[n], maxDepth - 1, seen);
+              printValue(str, *(*v.list)[n], maxDepth - 1, seen);
             } catch (AssertionError& e) {
               str << ESC_RED "«error: " << e.msg() << "»" ESC_END;
             }