title: why does lldb skips this line?
body: <p>I am currently trying to learn swift and while I was coding some dummy stuff, I noticed the xcode is skipping some lines and sometimes stops on weird lines . my env: macos sierra,xcode Version 8.2.1 (8C1002)</p>
  
  <p>since xcode is skipping some lines , I thought the problem is from code optimisation , then I switched to terminal to debug, below is the input&amp;output</p>
  
  <p>I compiled using </p>
  
  <pre><code>swiftc -g -Onone *.swift
  </code></pre>
  
  <p>then </p>
  
  <p>load it with lldb</p>
  
  <pre><code>lldb main
  </code></pre>
  
  <p>set breakpoint on lint 18 as shown below and process run with "r"</p>
  
  <pre><code>   17   do {
  -&gt; 18       try StaticM.teststatic2()
     19       print (1)
     20   }catch {
     21       
  (lldb) thread step-in
  Process 963 stopped
  * thread #1: tid = 0x86e1, 0x0000000100001f6a main`static StaticM.teststatic2(self=main.StaticM, $error=Error @ 0x00007fff5fbffac0) throws -&gt; () + 26 at staticExt.swift:13, queue = 'com.apple.main-thread', stop reason = step in
      frame #0: 0x0000000100001f6a main`static StaticM.teststatic2(self=main.StaticM, $error=Error @ 0x00007fff5fbffac0) throws -&gt; () + 26 at staticExt.swift:13
     10   public extension StaticM {
     11       @discardableResult
     12       public static func teststatic2() throws  {
  -&gt; 13           var asdf=2;
     14           let sdfgsdfg=2;
     15           print(sdfgsdfg);
     16           print (asdf);
  (lldb) n
  Process 963 stopped
  * thread #1: tid = 0x86e1, 0x0000000100001f72 main`static StaticM.teststatic2(self=main.StaticM, $error=Error @ 0x00007fff5fbffac0) throws -&gt; () + 34 at staticExt.swift:15, queue = 'com.apple.main-thread', stop reason = step over
      frame #0: 0x0000000100001f72 main`static StaticM.teststatic2(self=main.StaticM, $error=Error @ 0x00007fff5fbffac0) throws -&gt; () + 34 at staticExt.swift:15
     12       public static func teststatic2() throws  {
     13           var asdf=2;
     14           let sdfgsdfg=2;
  -&gt; 15           print(sdfgsdfg);
     16           print (asdf);
     17           asdf += 1;
     18       }
  (lldb) process continue
  Process 963 resuming
  2
  2
  1
  Process 963 exited with status = 0 (0x00000000) 
  (lldb)  
  </code></pre>
  
  <p>question is , after I go to next line using "n" in lldb, why lldb skips line 14 of staticExt.swift and jumps straight to line 15 ?</p>
  
  <p>also , sometimes when trying to debug some other program, I click on "step-in" in xcode, it stops on the declaration line of the func instead of first line in the code block, I clicked stepover , it goes back to the caller func line instead of executing the first line of that func.</p>
  
  <p>in all,programe works , but why lldb jumps even with -Onone and -g ? 
  could you please let me where can I find more info ?
  thank you very much.</p>