title: Where does the value of CXX in a makefile come from?
body: <p>Code Snippet:</p>
  
  <pre><code>target_test : test.cc 
      $(CXX) $(CPPFLAGS) $(CFLAGS) test.cc
  </code></pre>
  
  <p>I know that <code>CXX</code> is a variable (containing the compiler command to call), but I was wondering where this variable comes from. The variable is not defined in the makefile and is not an environment variable. Can anyone explain where the value of <code>CXX</code> comes from?</p>