after comment of Feng Xiao changed the entry to g++

src/README.md

@@ -17,12 +17,12 @@ To build protobuf from source, the following tools are needed:
   * libtool
   * curl (used to download gmock)
   * make
-  * clang (gcc)
+  * g++
   * unzip
 
 On Ubuntu, you can install them with:
 
-  $ sudo apt-get install autoconf automake libtool curl make clang unzip
+  $ sudo apt-get install autoconf automake libtool curl make g++ unzip
 
 On other platforms, please use the corresponding package managing tool to
 install them before proceeding.