5 files changed, 45 insertions, 40 deletions
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f94c23ea72bb..37b977736e28 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1316,7 +1316,8 @@ void EvalState::concatLists(Value & v, unsigned int nrLists, Value * * lists, co
     auto out = v.listElems();
     for (unsigned int n = 0, pos = 0; n < nrLists; ++n) {
         unsigned int l = lists[n]->listSize();
-        memcpy(out + pos, lists[n]->listElems(), l * sizeof(Value *));
+        if (l)
+            memcpy(out + pos, lists[n]->listElems(), l * sizeof(Value *));
         pos += l;
     }
 }
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 7b0a127cd41c..63cbef1ddf84 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -10,7 +10,7 @@ namespace nix {
 
 /* Displaying abstract syntax trees. */
 
-std::ostream & operator << (std::ostream & str, Expr & e)
+std::ostream & operator << (std::ostream & str, const Expr & e)
 {
     e.show(str);
     return str;
@@ -58,48 +58,48 @@ std::ostream & operator << (std::ostream & str, const Symbol & sym)
     return str;
 }
 
-void Expr::show(std::ostream & str)
+void Expr::show(std::ostream & str) const
 {
     abort();
 }
 
-void ExprInt::show(std::ostream & str)
+void ExprInt::show(std::ostream & str) const
 {
     str << n;
 }
 
-void ExprFloat::show(std::ostream & str)
+void ExprFloat::show(std::ostream & str) const
 {
     str << nf;
 }
 
-void ExprString::show(std::ostream & str)
+void ExprString::show(std::ostream & str) const
 {
     showString(str, s);
 }
 
-void ExprPath::show(std::ostream & str)
+void ExprPath::show(std::ostream & str) const
 {
     str << s;
 }
 
-void ExprVar::show(std::ostream & str)
+void ExprVar::show(std::ostream & str) const
 {
     str << name;
 }
 
-void ExprSelect::show(std::ostream & str)
+void ExprSelect::show(std::ostream & str) const
 {
     str << "(" << *e << ")." << showAttrPath(attrPath);
     if (def) str << " or (" << *def << ")";
 }
 
-void ExprOpHasAttr::show(std::ostream & str)
+void ExprOpHasAttr::show(std::ostream & str) const
 {
     str << "((" << *e << ") ? " << showAttrPath(attrPath) << ")";
 }
 
-void ExprAttrs::show(std::ostream & str)
+void ExprAttrs::show(std::ostream & str) const
 {
     if (recursive) str << "rec ";
     str << "{ ";
@@ -113,7 +113,7 @@ void ExprAttrs::show(std::ostream & str)
     str << "}";
 }
 
-void ExprList::show(std::ostream & str)
+void ExprList::show(std::ostream & str) const
 {
     str << "[ ";
     for (auto & i : elems)
@@ -121,7 +121,7 @@ void ExprList::show(std::ostream & str)
     str << "]";
 }
 
-void ExprLambda::show(std::ostream & str)
+void ExprLambda::show(std::ostream & str) const
 {
     str << "(";
     if (matchAttrs) {
@@ -143,7 +143,7 @@ void ExprLambda::show(std::ostream & str)
     str << ": " << *body << ")";
 }
 
-void ExprLet::show(std::ostream & str)
+void ExprLet::show(std::ostream & str) const
 {
     str << "(let ";
     for (auto & i : attrs->attrs)
@@ -155,27 +155,27 @@ void ExprLet::show(std::ostream & str)
     str << "in " << *body << ")";
 }
 
-void ExprWith::show(std::ostream & str)
+void ExprWith::show(std::ostream & str) const
 {
     str << "(with " << *attrs << "; " << *body << ")";
 }
 
-void ExprIf::show(std::ostream & str)
+void ExprIf::show(std::ostream & str) const
 {
     str << "(if " << *cond << " then " << *then << " else " << *else_ << ")";
 }
 
-void ExprAssert::show(std::ostream & str)
+void ExprAssert::show(std::ostream & str) const
 {
     str << "assert " << *cond << "; " << *body;
 }
 
-void ExprOpNot::show(std::ostream & str)
+void ExprOpNot::show(std::ostream & str) const
 {
     str << "(! " << *e << ")";
 }
 
-void ExprConcatStrings::show(std::ostream & str)
+void ExprConcatStrings::show(std::ostream & str) const
 {
     bool first = true;
     str << "(";
@@ -186,7 +186,7 @@ void ExprConcatStrings::show(std::ostream & str)
     str << ")";
 }
 
-void ExprPos::show(std::ostream & str)
+void ExprPos::show(std::ostream & str) const
 {
     str << "__curPos";
 }
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 30be79bb57a6..8c8f39640681 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -76,17 +76,17 @@ string showAttrPath(const AttrPath & attrPath);
 struct Expr
 {
     virtual ~Expr() { };
-    virtual void show(std::ostream & str);
+    virtual void show(std::ostream & str) const;
     virtual void bindVars(const StaticEnv & env);
     virtual void eval(EvalState & state, Env & env, Value & v);
     virtual Value * maybeThunk(EvalState & state, Env & env);
     virtual void setName(Symbol & name);
 };
 
-std::ostream & operator << (std::ostream & str, Expr & e);
+std::ostream & operator << (std::ostream & str, const Expr & e);
 
 #define COMMON_METHODS \
-    void show(std::ostream & str); \
+    void show(std::ostream & str) const; \
     void eval(EvalState & state, Env & env, Value & v); \
     void bindVars(const StaticEnv & env);
 
@@ -283,13 +283,13 @@ struct ExprOpNot : Expr
 };
 
 #define MakeBinOp(name, s) \
-    struct Expr##name : Expr \
+    struct name : Expr \
     { \
         Pos pos; \
         Expr * e1, * e2; \
-        Expr##name(Expr * e1, Expr * e2) : e1(e1), e2(e2) { }; \
-        Expr##name(const Pos & pos, Expr * e1, Expr * e2) : pos(pos), e1(e1), e2(e2) { }; \
-        void show(std::ostream & str) \
+        name(Expr * e1, Expr * e2) : e1(e1), e2(e2) { }; \
+        name(const Pos & pos, Expr * e1, Expr * e2) : pos(pos), e1(e1), e2(e2) { }; \
+        void show(std::ostream & str) const \
         { \
             str << "(" << *e1 << " " s " " << *e2 << ")";   \
         } \
@@ -300,14 +300,14 @@ struct ExprOpNot : Expr
         void eval(EvalState & state, Env & env, Value & v); \
     };
 
-MakeBinOp(App, "")
-MakeBinOp(OpEq, "==")
-MakeBinOp(OpNEq, "!=")
-MakeBinOp(OpAnd, "&&")
-MakeBinOp(OpOr, "||")
-MakeBinOp(OpImpl, "->")
-MakeBinOp(OpUpdate, "//")
-MakeBinOp(OpConcatLists, "++")
+MakeBinOp(ExprApp, "")
+MakeBinOp(ExprOpEq, "==")
+MakeBinOp(ExprOpNEq, "!=")
+MakeBinOp(ExprOpAnd, "&&")
+MakeBinOp(ExprOpOr, "||")
+MakeBinOp(ExprOpImpl, "->")
+MakeBinOp(ExprOpUpdate, "//")
+MakeBinOp(ExprOpConcatLists, "++")
 
 struct ExprConcatStrings : Expr
 {
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 6778023f506d..c88f677da085 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1601,12 +1601,16 @@ static void prim_partition(EvalState & state, const Pos & pos, Value * * args, V
     state.mkAttrs(v, 2);
 
     Value * vRight = state.allocAttr(v, state.sRight);
-    state.mkList(*vRight, right.size());
-    memcpy(vRight->listElems(), right.data(), sizeof(Value *) * right.size());
+    auto rsize = right.size();
+    state.mkList(*vRight, rsize);
+    if (rsize)
+        memcpy(vRight->listElems(), right.data(), sizeof(Value *) * rsize);
 
     Value * vWrong = state.allocAttr(v, state.sWrong);
-    state.mkList(*vWrong, wrong.size());
-    memcpy(vWrong->listElems(), wrong.data(), sizeof(Value *) * wrong.size());
+    auto wsize = wrong.size();
+    state.mkList(*vWrong, wsize);
+    if (wsize)
+        memcpy(vWrong->listElems(), wrong.data(), sizeof(Value *) * wsize);
 
     v.attrs->sort();
 }
diff --git a/src/libexpr/primops/fetchGit.cc b/src/libexpr/primops/fetchGit.cc
index 9fc0d46626dd..fd536c6a5e46 100644
--- a/src/libexpr/primops/fetchGit.cc
+++ b/src/libexpr/primops/fetchGit.cc
@@ -138,7 +138,7 @@ GitInfo exportGit(ref<Store> store, const std::string & uri,
     gitInfo.rev = rev != "" ? rev : chomp(readFile(localRefFile));
     gitInfo.shortRev = std::string(gitInfo.rev, 0, 7);
 
-    printTalkative("using revision %s of repo '%s'", uri, gitInfo.rev);
+    printTalkative("using revision %s of repo '%s'", gitInfo.rev, uri);
 
     std::string storeLinkName = hashString(htSHA512, name + std::string("\0"s) + gitInfo.rev).to_string(Base32, false);
     Path storeLink = cacheDir + "/" + storeLinkName + ".link";