From 9411299875cb8e49289500df64a568050bbf5dca Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 12 May 2022 20:37:18 +0200
Subject: [PATCH] Fix GC bug in ExprPath

---
 src/libexpr/eval.cc    |  5 +----
 src/libexpr/eval.hh    | 10 +++++-----
 src/libexpr/nixexpr.cc |  2 +-
 src/libexpr/nixexpr.hh |  8 ++++----
 src/libexpr/value.hh   |  8 ++++++++
 5 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 2c1b64d7f..4e1de843c 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -890,10 +890,7 @@ void Value::mkStringMove(const char * s, const PathSet & context)
 
 void Value::mkPath(const SourcePath & path)
 {
-    clearValue();
-    internalType = tPath;
-    _path.accessor = &path.accessor;
-    _path.path = makeImmutableString(path.path);
+    mkPath(&path.accessor, makeImmutableString(path.path));
 }
 
 
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 7d4d870f7..505f6e538 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -50,16 +50,16 @@ struct Env
 void copyContext(const Value & v, PathSet & context);
 
 
-// FIXME: maybe change this to an std::variant<SourcePath, URL>.
-typedef std::pair<std::string, std::string> SearchPathElem;
-typedef std::list<SearchPathElem> SearchPath;
-
-
 std::ostream & printValue(const EvalState & state, std::ostream & str, const Value & v);
 std::string printValue(const EvalState & state, const Value & v);
 std::ostream & operator << (std::ostream & os, const ValueType t);
 
 
+// FIXME: maybe change this to an std::variant<SourcePath, URL>.
+typedef std::pair<std::string, std::string> SearchPathElem;
+typedef std::list<SearchPathElem> SearchPath;
+
+
 /* Initialise the Boehm GC, if applicable. */
 void initGC();
 
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index c529fdc89..788859d2e 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -73,7 +73,7 @@ void ExprString::show(const SymbolTable & symbols, std::ostream & str) const
 
 void ExprPath::show(const SymbolTable & symbols, std::ostream & str) const
 {
-    str << s;
+    str << path;
 }
 
 void ExprVar::show(const SymbolTable & symbols, std::ostream & str) const
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 953e97419..2cb2aca3a 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -183,12 +183,12 @@ struct ExprString : Expr
 
 struct ExprPath : Expr
 {
-    std::string s; // FIXME: remove
+    const SourcePath path;
     Value v;
-    ExprPath(SourcePath && path)
-        : s(path.path)
+    ExprPath(SourcePath && _path)
+        : path(_path)
     {
-        v.mkPath(std::move(path));
+        v.mkPath(&path.accessor, path.path.c_str());
     }
     COMMON_METHODS
     Value * maybeThunk(EvalState & state, Env & env);
diff --git a/src/libexpr/value.hh b/src/libexpr/value.hh
index 9050a30ab..fb1139647 100644
--- a/src/libexpr/value.hh
+++ b/src/libexpr/value.hh
@@ -263,6 +263,14 @@ public:
 
     void mkPath(const SourcePath & path);
 
+    inline void mkPath(InputAccessor * accessor, const char * path)
+    {
+        clearValue();
+        internalType = tPath;
+        _path.accessor = accessor;
+        _path.path = path;
+    }
+
     inline void mkNull()
     {
         clearValue();