Je ne me souviens pas MDR LOL

doc/manual/command-ref/nix-instantiate.xml

@@ -43,6 +43,7 @@
       <arg choice='plain'><option>--expr</option></arg>
       <arg choice='plain'><option>-E</option></arg>
     </group>
+    <arg choice='plain'><option>--profile</option></arg>
     <arg choice='plain' rep='repeat'><replaceable>files</replaceable></arg>
   </cmdsynopsis>
   <cmdsynopsis>
@@ -162,6 +163,19 @@ input.</para>
 
   </varlistentry>
 
+  <varlistentry><term><option>--profile</option></term>
+
+    <listitem><para>When used with <option>--eval</option>, perform
+    evaluation in read/write mode so nix language features that
+    require it will still work (at the cost of needing to do
+    instantiation of every evaluated derivation). If this option is
+    not enabled, there may be uninstantiated store paths in the final
+    output.</para>
+
+    </listitem>
+
+  </varlistentry>
+
 </variablelist>
 
 <variablelist condition="manpage">

src/libexpr/eval.hh

@@ -10,6 +10,7 @@
 
 #include <map>
 #include <unordered_map>
+#include <array>
 
 
 namespace nix {
@@ -329,20 +330,20 @@ typedef int LineNumber;
 struct ProfFuncOcc {
     CompressedFuncId funcId;
     CompressedFileId fileId;
-}
-
-struct ProfCostOcc {
-    ProfFuncOcc funcOcc;
-    int selfCost;
-    Array<ProfFuncCall> calledFunctions;
-}
+};
 
 struct ProfFuncCall {
     CompressedFuncId calledFunc;
     CompressedFileId calledFile;
     LineNumber calledFuncLineNb;
     int cost;
-}
+};
+
+struct ProfCostOcc {
+    ProfFuncOcc funcOcc;
+    int selfCost;
+    std::array<ProfFuncCall, 100> calledFunctions;
+};
 
 class ProfilerState {
 
@@ -351,7 +352,7 @@ public:
     void saveCost(ProfCostOcc& occCost);
 
 private:
-    Array<ProfCostOcc> stackedMeasurements;
+    std::array<ProfCostOcc, 100> stackedMeasurements;
     string funcName;
     /* We index every func and file to leverage Callgrind's string compression.
        See section "3.1.6.<2E>Subposition Compression" section from [callgrindSpec]. */
@@ -359,7 +360,7 @@ private:
     std::map<CompressedFileId,FileName> fileMap;
     CompressedFuncId currentFuncId;
     CompressedFileId currentFileId;
-}
+};
 
 /* Return a string representing the type of the value `v'. */
 string showType(const Value & v);
@@ -401,8 +402,6 @@ struct EvalSettings : Config
     Setting<bool> traceFunctionCalls{this, false, "trace-function-calls",
         "Emit log messages for each function entry and exit at the 'vomit' log level (-vvvv)"};
 
-    Setting<bool> profileEvaluation(this, false, "profile-function-calls",
-        "Generates a callgraph profile summary which you can interpret using kcachegrind.");
 };
 
 extern EvalSettings evalSettings;

src/libstore/globals.hh

@@ -353,8 +353,10 @@ public:
 
     Setting<Paths> pluginFiles{this, {}, "plugin-files",
         "Plugins to dynamically load at nix initialization time."};
-};
 
+    Setting<bool> profileEvaluation{this, false, "profile-function-calls",
+        "Generates a callgraph profile summary which you can interpret using kcachegrind."};
+};
 
 // FIXME: don't use a global variable.
 extern Settings settings;

src/nix-instantiate/nix-instantiate.cc

@@ -140,6 +140,8 @@ static int _main(int argc, char * * argv)
                 repair = Repair;
             else if (*arg == "--dry-run")
                 settings.readOnlyMode = true;
+            else if (*arg == "--profile")
+                settings.profileEvaluation = true;
             else if (*arg != "" && arg->at(0) == '-')
                 return false;
             else