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Annotation of os2sdk/demos/examples/argument/argument.c, revision 1.1.1.2

1.1       root        1: /*
                      2:  * argument.c
                      3:  *
                      4:  * This program demonstrated a method of passing parameters to a thread.
                      5:  * Since Intel stacks grow down (High to low memory), and the PUSH instruction
                      6:  * decrements the pointer BEFORE writing to the stack, we do the same in C.
                      7:  *
                      8:  * The decrement before writing is important since the line:
                      9:  *
                     10:  *     threadStack += STACK_SIZE
                     11:  *
                     12:  * will place the pointer one element BEYOND the end of the stack.
                     13:  *
                     14:  * Also note that the stack is defined as a WORD array.  This is so the
                     15:  * decrement operator will adjust the stack by 2 with each push.
                     16:  *
                     17:  * One last caveat: what the thread expects upon the stack depends upon
                     18:  * how each argument is declared and the model that the program is being
                     19:  * compiled in.  KNOW YOUR C STACK STRUCTURE!
                     20:  *
                     21:  * Many of the C runtime library routines, including printf, are not
1.1.1.2 ! root       22:  * re-entrant. DosEnterCritSec & DosExitCritSec guarantee serial access
1.1       root       23:  * to the screen.
                     24:  *
1.1.1.2 ! root       25:  * Created by Microsoft Corp. 1988
1.1       root       26:  */
1.1.1.2 ! root       27: 
        !            28: #define INCL_DOSPROCESS
        !            29: 
        !            30: #include <os2def.h>
        !            31: #include <bsedos.h>
1.1       root       32: #include <stdio.h>
                     33: 
1.1.1.2 ! root       34: #define STACK_SIZE 512    /* stack size in WORDS (see malloc) */
1.1       root       35: 
                     36: main(ac, av)
                     37: char *av[];
                     38: int ac;
                     39: {
                     40:     void far thread();         /* address where thread gets control */
1.1.1.2 ! root       41:     PINT threadStack;          /* far pointer to thread stack (word)*/
        !            42:     TID threadID;              /* thread ID */
1.1       root       43:     unsigned rc;               /* return code */
                     44: 
                     45:     /* allocate stack space for thread */
1.1.1.2 ! root       46:     /* since this is written in C, DosAllocSeg cannot be used here */
1.1       root       47: 
                     48:     if ((threadStack = (int *)malloc(sizeof(int) * STACK_SIZE)) == NULL) {
                     49:        printf("thread stack malloc failed\n");
1.1.1.2 ! root       50:        DosExit(1, 1);  /* terminate all threads and return error */
1.1       root       51:     }
                     52:     threadStack += STACK_SIZE;         /* since stack grows down */
                     53: 
                     54:     *--threadStack = 0xFFFF;           /* Arg #5 = FFFF */
                     55:     *--threadStack = 0xEEEE;           /* Arg #4 ...    */
                     56:     *--threadStack = 0xDDDD;           /* Arg #3        */
                     57:     *--threadStack = 0xCCCC;
                     58:     *--threadStack = 0xBBBB;
                     59: 
1.1.1.2 ! root       60:     if (rc = DosCreateThread(thread, &threadID,
        !            61:             (PBYTE)threadStack)) {
1.1       root       62:        printf("create of thread failed, error: %d\n", rc);
1.1.1.2 ! root       63:        DosExit(1, 1);
1.1       root       64:     }
1.1.1.2 ! root       65:     DosEnterCritSec();
1.1       root       66:     printf("Thread ID = %d\n", threadID);
1.1.1.2 ! root       67:     DosExitCritSec();
1.1       root       68: 
1.1.1.2 ! root       69:     DosExit(0, 0);             /* Terminate, Let the other thread run */
1.1       root       70: }
                     71: 
                     72: 
                     73: /*
                     74:  * Thread process expects 5 arguments on the stack (normal C calling
                     75:  * convention).
                     76:  */
                     77: void far
                     78: thread(a1,a2,a3,a4,a5)
                     79: int a1,a2,a3,a4,a5;
                     80: {
1.1.1.2 ! root       81:     DosEnterCritSec();
1.1       root       82:     printf("Argument 1 = %x\n", a1);
1.1.1.2 ! root       83:     DosExitCritSec();
1.1       root       84: 
1.1.1.2 ! root       85:     DosEnterCritSec();
1.1       root       86:     printf("Argument 2 = %x\n", a2);
1.1.1.2 ! root       87:     DosExitCritSec();
1.1       root       88: 
1.1.1.2 ! root       89:     DosEnterCritSec();
1.1       root       90:     printf("Argument 3 = %x\n", a3);
1.1.1.2 ! root       91:     DosExitCritSec();
1.1       root       92: 
1.1.1.2 ! root       93:     DosEnterCritSec();
1.1       root       94:     printf("Argument 4 = %x\n", a4);
1.1.1.2 ! root       95:     DosExitCritSec();
1.1       root       96: 
1.1.1.2 ! root       97:     DosEnterCritSec();
1.1       root       98:     printf("Argument 5 = %x\n", a5);
1.1.1.2 ! root       99:     DosExitCritSec();
1.1       root      100: 
1.1.1.2 ! root      101:     DosExit(0,0);
1.1       root      102: }

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