title: Emacs g++ [no match] when trying to use g++ on minibuffer
body: <p>I'm new to Emacs and just trying to write helloworld on Emacs but when I type <code>M-x g++</code> and <code>space</code> or <code>RTN</code> the minibuffer display <code>M-x g++ [No match]</code>. I had installed g++, gcc, gdb.</p>
  
  <pre><code>g++ (Ubuntu 4.8.4-2ubuntu1~14.04.3) 4.8.4
  
  gcc (Ubuntu 4.8.4-2ubuntu1~14.04.3) 4.8.4
  
  GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1
  This GDB was configured as "x86_64-linux-gnu".
  </code></pre>
  
  <p>$PATH:</p>
  
  <pre><code>bash: /usr/bin/g++:/usr/bin/gcc:...
  </code></pre>
  
  <p>I also compiled hello.cpp:</p>
  
  <pre><code>Compilation started at Fri Sep 30 22:18:40  
  
  make -k 
  g++ -g -Wall -o hello hello.cpp   
  
  Compilation finished at Fri Sep 30 22:18:40
  </code></pre>