From bb6e6923f25841874b6a915d234d884ddd4c92dd Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 11 Apr 2019 23:04:13 +0200
Subject: [PATCH] Add environment variable NIX_SHOW_SYMBOLS for dumping the
 symbol table

---
 src/libexpr/eval.cc         | 6 ++++++
 src/libexpr/symbol-table.hh | 7 +++++++
 2 files changed, 13 insertions(+)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 211f7a55f..d8e10d9f2 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1811,6 +1811,7 @@ void EvalState::printStats()
             gc.attr("totalBytes", totalBytes);
         }
 #endif
+
         if (countCalls) {
             {
                 auto obj = topObj.object("primops");
@@ -1846,6 +1847,11 @@ void EvalState::printStats()
                 }
             }
         }
+
+        if (getEnv("NIX_SHOW_SYMBOLS", "0") != "0") {
+            auto list = topObj.list("symbols");
+            symbols.dump([&](const std::string & s) { list.elem(s); });
+        }
     }
 }
 
diff --git a/src/libexpr/symbol-table.hh b/src/libexpr/symbol-table.hh
index 44929f7ee..91faea122 100644
--- a/src/libexpr/symbol-table.hh
+++ b/src/libexpr/symbol-table.hh
@@ -75,6 +75,13 @@ public:
     }
 
     size_t totalSize() const;
+
+    template<typename T>
+    void dump(T callback)
+    {
+        for (auto & s : symbols)
+            callback(s);
+    }
 };
 
 }