Date: Sat, 15 Mar 1997 17:49:39 +0200 (SAT)
From: Alf Stockton <stockton AT fast DOT co DOT za>
Reply-To: Alf Stockton <stockton AT fast DOT co DOT za>
To: djgpp AT delorie DOT com
Subject: DJGPP and stdprn
Message-ID: <Pine.LNX.3.95.970315162537.114B-100000@localhost>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII

The following program compiles and runs clean under Watcom 10.? but when
compiled under DJGPP 2.0 with gcc bar.c gives no errors but at run time
crashes with SIGSEGV.

/*
 * bar.c - print barcode, 3-of-9, external printer interface
 */
#define TEST
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static void PrintBar(int, int); /* print thick or thin line or space */
static void PrinterInitialise(char *);      /* initialize            */
static void PrintFinished(void);            /* finish                */
static void BarCode(unsigned short);

/*
 * These codes represent the 3-of-9 encoding.  Note that there are exactly
 *      three 1-bits in each code.  Those are the "thick" lines/spaces.
 *      The barcode alternates between lines and spaces - the codes below
 *      determine the width of each line or space, not whether it's a line
 *      or a space.
 */
static unsigned short Codes[] =
    {
    0xc4,  0x00,  0x00, 0x00,  0xa8,  0x2a,  0x00, 0x00,  0x00, 0x00,
    0x00,  0x8a,  0x00, 0x85,  0x184, 0xa2,  0x34, 0x121, 0x61, 0x160,
    0x31,  0x130, 0x70, 0x25,  0x124, 0x64,  0x00, 0x00,  0x00, 0x00,
    0x00,  0x00,  0x00, 0x109, 0x49,  0x148, 0x19, 0x118, 0x58, 0x0d,
    0x10c, 0x4c,  0x1c, 0x103, 0x43,  0x142, 0x13, 0x112, 0x52, 0x07,
    0x106, 0x46,  0x16, 0x181, 0x0c1, 0x1c0, 0x91, 0x190, 0x0d0
    };

static short int Resolution = 2; // horizontal settings for width of barcode
static short int Depth = 4;      // lines deep/height of barcode

void bar(char *String)
    {
    short int i;
    int ReturnCode;
    char *s;

    for(i = Depth; i > 0; --i)
        {
        ReturnCode = fprintf(stdprn,"\n");
        s = String;
        PrinterInitialise(s);
        BarCode(0x94);                    // start code
        while(*s)
            {
            BarCode(Codes[*s - ' ']);
            ++s;
            }
        BarCode(0x94);                    // stop code
        }
    PrintFinished();
    }

void BarCode(unsigned short c)
    {
    int line;                          // BOOL line/space
    unsigned short mask = 0x100;

    for(line = 1; mask; line = 1 - line)
        {
        PrintBar(c & mask, line);
        mask >>= 1;
        }
    PrintBar(0, 0);            /* finish each char with a thin space */
    }

/*
 * initialize the printer as required to print string s
 * the ratio of thick to thin is 3:1, and there will be 3 thicks and 6 thins.
 * each character is terminated by a thin space.
 * thus, each character is 16 * res dots wide (res * 6 + 3*res * 3 + res)
 * each string starts and stops with a special code, so there are
 * strlen(s) + 2 bytes to print.
 */
void PrinterInitialise(char *s)
    {
    unsigned short n;

    n = 16 * Resolution * (strlen(s) + 2);    // total # of graphic bytes
    fprintf(stdprn,"%c%c%c", 0x1b, 0x33, 0x10); // n/216th of an inch line feed
    fprintf(stdprn,"%c%c%c%c", 0x1b, 0x4c, n & 0xff, n >> 8); // 120 DPI graphics
    }

/*
 * This is the place to put any other printer reset commands you want,
 *      like 6 LPI, condensed print, or whatever.
 */
void PrintFinished()
    {
    fprintf(stdprn,"%c%c", 0x0d, 0x0a); // carriage return & line feed
    fprintf(stdprn,"%c%c",0x1b,0x30);   // 1/8" line feed
    fprintf(stdprn,"%c%c",0x1b,0x40);   // re-initialise printer
    }

/*
 * print an individual line or space, thick or thin
 * args are boolean
 */
void PrintBar(int thick, int line)
    {
    short int w, c;

    w = Resolution * (thick ? 3 : 1);
    c = line ? 0xff : 0;
    while(w--)
        {
        fprintf(stdprn,"%c", c);
        }
    }

#ifdef TEST
int main(int argc, char *argv[])
    {
    fprintf(stdprn, "987654321\n");
    bar("987654321");
    return(0);
    }
#endif

What have I done wrong ? 
I suspect that GCC knows nothing of stdprn and that Watcom, Turbo/Borland
C and MicroSoft do. If GCC doesn't why don't I get a compile error ?
I have not found any reference in info but maybe I haven't looked far
enough.

Regards,
Alf Stockton	stockton AT fast DOT co DOT za