2 files changed, 23 insertions, 9 deletions

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 353097f89713..2473157b3f63 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -307,6 +307,8 @@ EvalState::EvalState(const Strings & _searchPath, ref<Store> store)
 
     assert(gcInitialised);
 
+    static_assert(sizeof(Env) == 16);
+
     /* Initialise the Nix expression search path. */
     if (!settings.pureEval) {
         Strings paths = parseNixPath(getEnv("NIX_PATH", ""));
@@ -352,6 +354,10 @@ Path EvalState::checkSourcePath(const Path & path_)
 {
     if (!allowedPaths) return path_;
 
+    auto i = resolvedPaths.find(path_);
+    if (i != resolvedPaths.end())
+        return i->second;
+
     bool found = false;
 
     for (auto & i : *allowedPaths) {
@@ -369,8 +375,10 @@ Path EvalState::checkSourcePath(const Path & path_)
     Path path = canonPath(path_, true);
 
     for (auto & i : *allowedPaths) {
-        if (isDirOrInDir(path, i))
+        if (isDirOrInDir(path, i)) {
+            resolvedPaths[path_] = path;
             return path;
+        }
     }
 
     throw RestrictedPathError("access to path '%1%' is forbidden in restricted mode", path);
@@ -562,12 +570,12 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
     if (!var.fromWith) return env->values[var.displ];
 
     while (1) {
-        if (!env->haveWithAttrs) {
+        if (env->type == Env::HasWithExpr) {
             if (noEval) return 0;
             Value * v = allocValue();
             evalAttrs(*env->up, (Expr *) env->values[0], *v);
             env->values[0] = v;
-            env->haveWithAttrs = true;
+            env->type = Env::HasWithAttrs;
         }
         Bindings::iterator j = env->values[0]->attrs->find(var.name);
         if (j != env->values[0]->attrs->end()) {
@@ -597,6 +605,7 @@ Env & EvalState::allocEnv(size_t size)
     nrValuesInEnvs += size;
     Env * env = (Env *) allocBytes(sizeof(Env) + size * sizeof(Value *));
     env->size = (decltype(Env::size)) size;
+    env->type = Env::Plain;
 
     /* We assume that env->values has been cleared by the allocator; maybeThunk() and lookupVar fromWith expect this. */
 
@@ -1199,7 +1208,7 @@ void ExprWith::eval(EvalState & state, Env & env, Value & v)
     Env & env2(state.allocEnv(1));
     env2.up = &env;
     env2.prevWith = prevWith;
-    env2.haveWithAttrs = false;
+    env2.type = Env::HasWithExpr;
     env2.values[0] = (Value *) attrs;
 
     body->eval(state, env2, v);
@@ -1857,9 +1866,10 @@ size_t valueSize(Value & v)
 
         size_t sz = sizeof(Env) + sizeof(Value *) * env.size;
 
-        for (size_t i = 0; i < env.size; ++i)
-            if (env.values[i])
-                sz += doValue(*env.values[i]);
+        if (env.type != Env::HasWithExpr)
+            for (size_t i = 0; i < env.size; ++i)
+                if (env.values[i])
+                    sz += doValue(*env.values[i]);
 
         if (env.up) sz += doEnv(*env.up);
 
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 86e93a5ac9ce..3725e45dad9b 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -7,6 +7,7 @@
 #include "hash.hh"
 
 #include <map>
+#include <unordered_map>
 
 
 namespace nix {
@@ -34,8 +35,8 @@ struct Env
 {
     Env * up;
     unsigned short size; // used by ‘valueSize’
-    unsigned short prevWith:15; // nr of levels up to next `with' environment
-    unsigned short haveWithAttrs:1;
+    unsigned short prevWith:14; // nr of levels up to next `with' environment
+    enum { Plain = 0, HasWithExpr, HasWithAttrs } type:2;
     Value * values[0];
 };
 
@@ -100,6 +101,9 @@ private:
 
     std::map<std::string, std::pair<bool, std::string>> searchPathResolved;
 
+    /* Cache used by checkSourcePath(). */
+    std::unordered_map<Path, Path> resolvedPaths;
+
 public:
 
     EvalState(const Strings & _searchPath, ref<Store> store);