Ellipsis use with C51 for 8051

ellipsis_40 must be a global variable in the c51s.lib (or whatever model you use). It means you can place up to 40 byte on the stack for a variadatic function. Obviously, this is quite non-standard and you should use varargs if you can, they are macros and should not invoke any libary function calls. Also, when posting code, bracket it completey with
< pre > and < /pre > but without the spaces between the < and >.

This is a quick example for you to try:

#include <stdarg.h>

typedef unsigned char U8;

void variable(U8 *inBfrPtr, U8 *pFormat, ...)
{
    va_list    vargList;
    U8         argList[MAX_ARG_SIZE];
    U8         idx      = 0;
    U8         numArgs  = 0;

    // Extract the arguments, I'm assuming all char's. Also, you'll want to loop
    // on the va_arg() extraction based upon your pFormat.
    va_start(vargList, pFormat);
    argList[idx] = va_arg(vargList, U8);
    va_end(vargList);
}

ellipsis_40 must be a global variable in the c51s.lib (or whatever model you use). It means you can place up to 40 byte on the stack for a variadatic function. Obviously, this is quite non-standard and you should use varargs if you can, they are macros and should not invoke any libary function calls. Also, when posting code, bracket it completey with
< pre > and < /pre > but without the spaces between the < and >.

This is a quick example for you to try:

#include <stdarg.h>

typedef unsigned char U8;

void variable(U8 *inBfrPtr, U8 *pFormat, ...)
{
    va_list    vargList;
    U8         argList[MAX_ARG_SIZE];
    U8         idx      = 0;
    U8         numArgs  = 0;

    // Extract the arguments, I'm assuming all char's. Also, you'll want to loop
    // on the va_arg() extraction based upon your pFormat.
    va_start(vargList, pFormat);
    argList[idx] = va_arg(vargList, U8);
    va_end(vargList);
}

you might want to set up an XDATA reentrant stack and then define all your variadatic functions (only them) as reentrant, I did it like this:

void variable(U8 *inBfrPtr, U8 *pFormat, ...) large reentrant
{
   
}

I *really* appreciate your feedback. Please excuse my ignorance, but I am not following you too well.

I modified the original posted code to the following and it does compile. Does it look right? I am unsure about where to put va_end/start.

<pre >
int sscanf(char *inBfrPtr, char *fmtPtr, ...)
{
Byte scanResult = 0;
// void *argPtr = &ellipsis_40;
void *argPtr;
register char tmpDigit;

va_list vargList;
Byte argList[40];

va_start(vargList, fmtPtr);
argList[0] = va_arg(vargList, Byte);
argPtr = &argList[0];

while(1){
if(*fmtPtr == '\0')
break;
else if(*fmtPtr == '%'){
fmtPtr++;
if(*fmtPtr == 'c'){
**(char **)argPtr = *inBfrPtr;
argPtr += 3;
fmtPtr++;
inBfrPtr++;
scanResult += 1;
continue;
}
else if(*fmtPtr == 'd'){
if(inBfrPtr[0] == '+' || inBfrPtr[0] == '-')
tmpDigit = inBfrPtr[1];
else
tmpDigit = inBfrPtr[0];
if(tmpDigit >= '0' && tmpDigit <= '9'){
**(int **)argPtr = atoi(inBfrPtr);
while(1){
inBfrPtr++;
if(inBfrPtr[0] < '0' || inBfrPtr[0] > '9')
break;
}
fmtPtr++;
argPtr += 3;
scanResult += 1;
continue;
}
else
break;
}
else if(*fmtPtr == '%'){
/* fall through to continue string comparison */
}
else{ /* unknown format specifier */
break;
}
}
if(*fmtPtr++ != *inBfrPtr++)
break;
}
return(scanResult);
va_end(vargList);
}

</pre >

Okay, we will get this pre tag to work. It's < pre > but *no* spaces after the < or before the >. I can't show it literally here of course. Hit the preview tab as you reply to see that you are getting blue highlighted, fixed pitch code blocks. Of course < /pre > is the < pre > terminator. Again, *no spaces* are allowed. It's really hard to read proportionally spaced code without indentation.

Now on to the problem. You missed my point that I made poorly. You pop things off the variadatic stack which is made known to the compiler via the va_start() macro. You pop things off using the type you expect by using the va_arg() macro. Then you terminate your variadatic stack usage with the va_end() macro. Here's a printf() example (watch my < pre >):

int printf(char *pFmt, ...) reentrant large
{
    long fourByte;
    short twoByte;
    char byte;
    int count;
    va_list vargList;

    va_start(vargList, pFmt);
    while (*pFmt)
    {
        if (!strcmp(pFmt, "%c"))
        {
             byte = va_arg(vargList, char);
             ++count;
        }
        else if ((!strcmp(pFmt, "%d")))
        {
             twoByte = va_arg(vargList, short);
             count += sizeof (short)
        }
        else if ((!strcmp(pFmt, "%ld")))
        {
             fourByte = va_arg(vargList, long);
             count += sizeof (long);
        }
        
        // Important, move along through the variadatic stack.
        ++pFmt;
    }

    // All done
    va_end(vargList);

    return count;
}

"I can't show it literally here of course."

If you type "&amplt" and "&ampgt" in the 'post' window, they will display as '<' and '>'
Thus you can show the &ltpre&gt and &lt/pre&gt literally in your post!

The ampersand, '&amp', is the standard HTML escape; of course, to show it here, I had to use the escape sequence for ampersand, which is "&ampamp".
You should be able to see how it all works with your Browser's 'View Source' button, or equivalent.

To check how your post will look, use the 'Preview' button below the 'Post' window (and then your Browser's 'Back' button if you need further editing).

Hmm... &ltpre&gt hey neat. Now why couldn't they just use the \ for escape? That seems so much better to me, of course I'm a C programmer too.

Thanks Andrew.

- Mark