title: What functions is the libm intended for?
body: <p>As far as I know some math functions are contained in libc, while others are in  libm.  I've discovered that experimentally:</p>
  
  <pre><code>$ nm --dynamic --defined-only /lib/x86_64-linux-gnu/libm.so.6 | grep -w abs 
  $ nm --dynamic --defined-only /lib/x86_64-linux-gnu/libc.so.6 | grep -w abs 
  T abs
  </code></pre>
  
  <p>Is there a requirement concerning which mathematical functions must be provided by libm? Does libc and libm together provide all the math functions required by C standard?</p>