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anecdotes:not_expected_to_understand_this [2016/01/12 10:32] wktanecdotes:not_expected_to_understand_this [2016/01/12 10:33] wkt
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      */      */
     if(rp->p_flag&SSWAP) {     if(rp->p_flag&SSWAP) {
-   rp->p_flag =& ~SSWAP;+        rp->p_flag =& ~SSWAP;
         aretu(u.u_ssav);         aretu(u.u_ssav);
     }     }
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 </code> </code>
  
-  So we tried to explain what was going on. "You are not expected to understand this" was intended as a remark in the spirit of "This won't be on the exam," rather than as an impudent challenge.+So we tried to explain what was going on. "You are not expected to understand this" was intended as a remark in the spirit of "This won't be on the exam," rather than as an impudent challenge.
  
 The real problem is that we didn't understand what was going on either. The savu/retu mechanism for doing process exchange was fundamentally broken because it depended on switching to a previous stack frame and executing function return code in a different procedure from the one that saved the earlier state. This worked on the PDP-11 because its compiler always used the same context-save mechanism; with the Interdata compiler, the procedure return code differed depending on which registers were saved. The real problem is that we didn't understand what was going on either. The savu/retu mechanism for doing process exchange was fundamentally broken because it depended on switching to a previous stack frame and executing function return code in a different procedure from the one that saved the earlier state. This worked on the PDP-11 because its compiler always used the same context-save mechanism; with the Interdata compiler, the procedure return code differed depending on which registers were saved.
anecdotes/not_expected_to_understand_this.txt · Last modified: 2022/07/08 09:22 by 192.99.0.24