title: what's mean about "compact unwind info" in linker synthesized
body: <p>When I analyze the link map file which was generated by xcode, in the linker syntheized section, there is a data named "compact unwind info".</p>
  
  <pre><code>compact unwind info 858.57KB    858572  Unchecked
  </code></pre>
  
  <p>it take about 858kb space size.
  I want to know what the actual data in this space.
  it there any way to reduce this size?</p>
  
  <p>the total output of linker synthesized section:</p>
  
  <pre><code>compact unwind info 858.57KB
  helper helper   24B
  objc image info 8B
  non-lazy-pointer    8B
  non-lazy-pointer-to-local: dyld_stub_binder 8B
  non-lazy-pointer-to-local: _vm_page_size    8B
  non-lazy-pointer-to-local: _tanh    8B
  non-lazy-pointer-to-local: _tan 8B
  non-lazy-pointer-to-local: _strdup  8B
  non-lazy-pointer-to-local: _strcmp  8B
  non-lazy-pointer-to-local: _sinh    8B
  non-lazy-pointer-to-local: _sin 8B
  non-lazy-pointer-to-local: _realloc 8B
  non-lazy-pointer-to-local: _protocol_getName    8B
  non-lazy-pointer-to-local: _object_getIndexedIvars  8B
  non-lazy-pointer-to-local: _objc_readClassPair  8B
  non-lazy-pointer-to-local: _objc_lookUpClass    8B
  non-lazy-pointer-to-local: _objc_getRequiredClass   8B
  non-lazy-pointer-to-local: _objc_getProtocol    8B
  non-lazy-pointer-to-local: _objc_getMetaClass   8B
  non-lazy-pointer-to-local: _objc_getClass   8B
  non-lazy-pointer-to-local: _objc_copyClassNamesForImage 8B
  non-lazy-pointer-to-local: _objc_allocateClassPair  8B
  non-lazy-pointer-to-local: _malloc  8B
  non-lazy-pointer-to-local: _mach_task_self_ 8B
  .....
  </code></pre>