archive: check close errors when extracting nars

src/libstore/nar-accessor.cc

@@ -75,6 +75,9 @@ struct NarAccessor : public FSAccessor
             createMember(path, {FSAccessor::Type::tRegular, false, 0, 0});
         }
 
+        void closeRegularFile() override
+        { }
+
         void isExecutable() override
         {
             parents.top()->isExecutable = true;

src/libutil/archive.cc

@@ -234,6 +234,7 @@ static void parse(ParseSink & sink, Source & source, const Path & path)
 
         else if (s == "contents" && type == tpRegular) {
             parseContents(sink, source, path);
+            sink.closeRegularFile();
         }
 
         else if (s == "executable" && type == tpRegular) {
@@ -324,6 +325,12 @@ struct RestoreSink : ParseSink
         if (!fd) throw SysError("creating file '%1%'", p);
     }
 
+    void closeRegularFile() override
+    {
+        /* Call close explicitly to make sure the error is checked */
+        fd.close();
+    }
+
     void isExecutable() override
     {
         struct stat st;

src/libutil/archive.hh

@@ -60,6 +60,7 @@ struct ParseSink
     virtual void createDirectory(const Path & path) { };
 
     virtual void createRegularFile(const Path & path) { };
+    virtual void closeRegularFile() { };
     virtual void isExecutable() { };
     virtual void preallocateContents(uint64_t size) { };
     virtual void receiveContents(std::string_view data) { };