Revert "Prevent config.h from being clobbered"

This reverts commit 28bba8c44f484eae38e8a15dcec73cfa999156f6.

4 files changed, 23 insertions, 5 deletions

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 676dd3ac461a..a1613a4205b4 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -966,7 +966,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
            since paths are copied when they are used in a derivation),
            and none of the strings are allowed to have contexts. */
         if (first) {
-            isPath = vStr.type == tPath;
+            isPath = !forceString && vStr.type == tPath;
             first = false;
         }
 
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index bc6c3287c79d..86a7bfd506a0 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -277,8 +277,10 @@ MakeBinOp(OpConcatLists, "++")
 
 struct ExprConcatStrings : Expr
 {
+    bool forceString;
     vector<Expr *> * es;
-    ExprConcatStrings(vector<Expr *> * es) : es(es) { };
+    ExprConcatStrings(bool forceString, vector<Expr *> * es)
+        : forceString(forceString), es(es) { };
     COMMON_METHODS
 };
 
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 1819da5e1caa..66edfb548b32 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -203,7 +203,7 @@ static Expr * stripIndentation(SymbolTable & symbols, vector<Expr *> & es)
         es2->push_back(new ExprString(symbols.create(s2)));
     }
 
-    return es2->size() == 1 ? (*es2)[0] : new ExprConcatStrings(es2);
+    return es2->size() == 1 ? (*es2)[0] : new ExprConcatStrings(true, es2);
 }
 
 
@@ -318,7 +318,7 @@ expr_op
     { vector<Expr *> * l = new vector<Expr *>;
       l->push_back($1);
       l->push_back($3);
-      $$ = new ExprConcatStrings(l);
+      $$ = new ExprConcatStrings(false, l);
     }
   | expr_op CONCAT expr_op { $$ = new ExprOpConcatLists($1, $3); }
   | expr_app
@@ -349,7 +349,7 @@ expr_simple
       /* For efficiency, and to simplify parse trees a bit. */
       if ($2->empty()) $$ = new ExprString(data->symbols.create(""));
       else if ($2->size() == 1) $$ = $2->front();
-      else $$ = new ExprConcatStrings($2);
+      else $$ = new ExprConcatStrings(true, $2);
   }
   | IND_STRING_OPEN ind_string_parts IND_STRING_CLOSE {
       $$ = stripIndentation(data->symbols, *$2);
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index f8f893d69683..f66b24b7708a 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1107,6 +1107,21 @@ static void prim_unsafeDiscardOutputDependency(EvalState & state, Value * * args
 }
 
 
+/* Return the cryptographic hash of a string in base-16. */
+static void prim_hashString(EvalState & state, Value * * args, Value & v)
+{
+    string type = state.forceStringNoCtx(*args[0]);
+    HashType ht = parseHashType(type);
+    if (ht == htUnknown)
+      throw Error(format("unknown hash type `%1%'") % type);
+
+    PathSet context; // discarded
+    string s = state.forceString(*args[1], context);
+
+    mkString(v, printHash(hashString(ht, s)), context);
+};
+
+
 /*************************************************************
  * Versions
  *************************************************************/
@@ -1234,6 +1249,7 @@ void EvalState::createBaseEnv()
     addPrimOp("__stringLength", 1, prim_stringLength);
     addPrimOp("__unsafeDiscardStringContext", 1, prim_unsafeDiscardStringContext);
     addPrimOp("__unsafeDiscardOutputDependency", 1, prim_unsafeDiscardOutputDependency);
+    addPrimOp("__hashString", 2, prim_hashString);
 
     // Versions
     addPrimOp("__parseDrvName", 1, prim_parseDrvName);