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   PASCAL_LESSONS      Pascal Programming Lessons      361 messages   

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   Message 324 of 361   
   Anton Shepelev to All   
   TP 7.0 pointer passing convension   
   15 Feb 20 20:33:48   
   
   MSGID: 2:221/360.0 5e483984   
   PID: Sylpheed 3.7.0 (GTK+ 2.24.30; i686-pc-mingw32)   
   CHRS: IBMPC 2   
   TZUTC: 0200   
   Hello, all   
      
   The Language Guide for Turbo Pascal 7.0 says:   
      
      Variable  parameters  (var parameters) are always   
      passed by reference--a pointer that points to the   
      actual storage location.   
      [...]   
      A  pointer-type  parameter is passed as two words   
      (a double word).   The  segment  part  is  pushed   
      before  the  offset  part so that the offset part   
      ends up at the lowest address.   
      
   I have written the following proceudre that adds its   
   first argument to the second:   
      
   procedure AtoB(a: byte; var b: byte);   
   begin asm   
      PUSH  AX           { store AX                 }   
      MOV   DI,  [BP+4]  { store offset  of b in DI }   
      MOV   ES,  [BP+2]  { store segment of b in ES }   
      MOV   AX,  [BP+8]  { store a in AX            }   
      MOV  [DI],  AX     { assign AX to a           }   
      POP   AX           { restore AX               }   
   end end;   
      
   Does not it show that the TP documentation is in er-   
   ror, and pointers are put on stack backwards?   
      
   ---   
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