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AndersG
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2020/11/30 03:49:33 (permalink)
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Another "generates no code"

But I fail to see why, ie total_bytes is a local DWORD. nbytes (UINT) is updated by f_read and that is then added to total_bytes
 
 total_bytes = 0;

 for(i=0;i<chunks;i++) // Read maximum 256 bytes
 {
  if(i==(chunks-1) && tail == 0) gpib_flags = gpib_flags | FLAGS_EOI; // EOI on, on last block if there is no tail

        rc=f_read(&File[Unit],gpib_tx_buff,256,&nbytes);

#if SDEBUG >= 1
  xprintf("\r\n%02X%02X 1:Read rtn %X, %d read ", TMR1H, TMR1L, rc, nbytes);
#endif
  if(rc != 0)
  {
   SS80Disk[Unit].Errors = SS80Disk[Unit].Errors | SS80_ERR_SEEK;
   SS80_error_return(); // return one byte and
   return rc2; // bail out if seek fails
  }
  //Time();
  sendgpib(nbytes);
  total_bytes = total_bytes + nbytes;
  SS80Disk[Unit].Vector = SS80Disk[Unit].Vector + 0x100L;
#if SDEBUG >= 1
  xprintf("\r%02X%02X Vector %ld (%lX) ", TMR1H, TMR1L, SS80Disk[Unit].Vector, SS80Disk[Unit].Vector);
#endif
 }

 
 
#1

6 Replies Related Threads
    AndersG
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    Re: Another "generates no code" 2020/11/30 04:29:50 (permalink)
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    Here is another, says that total_bytes and RC are not used. But they are sendgpib is int sendgpib (int len); f_read is FRESULT f_read (FIL* fp, void* buff, UINT btr, UINT* br);
     
    // Do a buffered read of the current sector
    //
    void amigo_cmd_buffered_read()
    {
    DWORD total_bytes;
    FRESULT rc;
    UINT nbytes;
    UINT sbytes;
          // Follows after 0x680x05, Send 256 bytes. EOI only if error
    #if SDEBUG >= 1
     xprintf("\r\nAM:Buff rd c/h/s: %d/%d/%d s:%ld ", AmigoDisk[Unit].cyl, AmigoDisk[Unit].head, AmigoDisk[Unit].sector,
      (DWORD)AmigoDisk[Unit].cyl*16L*2L + (DWORD)AmigoDisk[Unit].head *16L + (DWORD)AmigoDisk[Unit].sector
     );
    #endif
     //
        DISK_LED = 1;
        DisablePP();
     total_bytes = 0;
     rc=f_read(&File[Unit],gpib_tx_buff,256,&nbytes);
    #if SDEBUG >= 1
      xprintf("\r\nRead rtn %X, %d bytes read", rc, nbytes);
    #endif
        //trigger(1);
     gpib_flags = gpib_flags & ~FLAGS_EOI;
     sbytes=sendgpib(nbytes);
     total_bytes = total_bytes + sbytes;
    #if SDEBUG >= 1
     xprintf("\r\n %ld bytes sent", total_bytes);
    #endif
     dsj = 0;
        DISK_LED = 0;
     EnablePP(); 
    }

    #2
    ric
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    Re: Another "generates no code" 2020/11/30 04:49:34 (permalink)
    0 (2)
    AndersG
    But I fail to see why, ie total_bytes is a local DWORD. nbytes (UINT) is updated by f_read and that is then added to total_bytes
     ...

    Nothing in that code ever uses the value of "total_bytes", so why should it bother maintaining it?
    If the only use for a variable is to examine it in a debugger WATCH window, then you must add a "volatile" qualifier to it to stop the compiler discarding it altogether.
     
    post edited by ric - 2020/11/30 04:50:46

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    #3
    ric
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    Re: Another "generates no code" 2020/11/30 04:58:51 (permalink)
    -1 (1)
    AndersG
    Here is another, says that total_bytes and RC are not used.
    ...



    The only code using that value is inside "#if SDEBUG >= 1"
    You don't show the #define for SDEBUG, or mention what value it is.
     

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    AndersG
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    Re: Another "generates no code" 2020/11/30 04:59:28 (permalink)
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    Thanks! That was it. Yes it is only used for debugging. I never thought the compiler was that smart :) I will make it volatile
     
    Sorry SDEBUG is a define I have to enable debugging output over serial.
    post edited by AndersG - 2020/11/30 05:01:48
    #5
    ric
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    Re: Another "generates no code" 2020/11/30 05:04:08 (permalink)
    0 (2)
    AndersG
    ...
    Sorry SDEBUG is a define I have to enable debugging output over serial.

    That's obvious, but if you don't define it (or if it's less than 1) then the code inside the #if is discarded, so the variable becomes unused, and will be discarded.
     

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    AndersG
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    Re: Another "generates no code" 2020/11/30 08:13:30 (permalink)
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    Yes. You are so right. Did not think that far.
    #7
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