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Dos16SysTrace writes a trace record to the system trace buffer. It provides a high speed event recording mechanism which may be used by PM and non-PM threads in ring 3 and ring 2 and by detached processes.


       (USHORT major, USHORT cBuffer, USHORT minor, PCHAR pBuffer) 


major (USHORT) input 
Major code which identifies the trace record. Range reserved for user. :Use is 245-255.
Valid range 0-255
cBuffer (USHORT) input 
Length of optional buffer. Valid range
  • 0 - 512 (before 4.0 FP 10 and 3.0 FP 35)
  • 0 - 4099 (from 3.0 FP35 and 4.0 FP10 onwards).
minor (USHORT) input 
Minor code which identifies the trace record. Major-minor code pair should uniquely identify the trace record.
Valid range 1 - 255
pBuffer (PCHAR) input 
Pointer to optional buffer. If cBuffer is 0, then pBuffer is ignored.

Return Code

ulrc (APIRET) returns

Dos16SysTrace returns one of the following values

  • 0 NO_ERROR


Dos16SysTrace creates a trace record that includes the following items:

  • Header Major code, minor code, time stamp, PID of logging process
  • Optional System Data Controlled by the TRACE command
  • Optional User Data Specified by the pBuffer parameter

If you use Dos16SysTrace, then you need to LINK specifying OS2386.LIB. If you use DosSysTrace, then you need to LINK specifying OS2286.LIB as an additional library file with the LINK386 command.

Example Code

int main(int argc, char *argv[], char *envp[]){
   APIRET16 rc=0;          /* default return code */
   USHORT major=255;       /* default major code */
   USHORT minor=1;         /* default minor code */
   USHORT cBuffer=0;       /* default buffer length */
   PCHAR  pBuffer=NULL;    /* default buffer address */

   if (argc>1)
      pBuffer = argv[1];
      cBuffer = strlen(argv[1]);

   if (argc>2) major = atol(argv[2]);
   if (argc>3) minor = atol(argv[3]);

   rc = Dos16SysTrace(major, cBuffer, minor, pBuffer);

   if (rc) printf("DosSysTrace retuned rc=%u\n", rc);

   return rc;

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