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Forum index » Advanced Topics » Additional Software (PETs, n' stuff) » Compiling

How do I compile this tiny C program?

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sc0ttman

Joined: 16 Sep 2009
Posts: 2174
Location: UK

Posted: Sat 13 Aug 2011, 13:46 Post subject:

How do I compile this tiny C program?

I have tried to compile the C program below many times, with many different gcc commands, and I always get an error saying 'undefined reference to `main'..

Here's the source code of the program:

Code:

/*
Copyright 2001, 2002 Georges Menie (www.menie.org)

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/

/*
putchar is the only external dependency for this file,
if you have a working putchar, just remove the following
define. If the function should be called something else,
replace outbyte(c) by your own function call.
*/
#define putchar(c) outbyte(c)

static void printchar(char **str, int c)
{
extern int putchar(int c);
if (str) {
   **str = c;
   ++(*str);
}
else (void)putchar(c);
}

#define PAD_RIGHT 1
#define PAD_ZERO 2

static int prints(char **out, const char *string, int width, int pad)
{
register int pc = 0, padchar = ' ';

if (width > 0) {
   register int len = 0;
   register const char *ptr;
   for (ptr = string; *ptr; ++ptr) ++len;
   if (len >= width) width = 0;
   else width -= len;
   if (pad & PAD_ZERO) padchar = '0';
}
if (!(pad & PAD_RIGHT)) {
   for ( ; width > 0; --width) {
      printchar (out, padchar);
      ++pc;
   }
}
for ( ; *string ; ++string) {
   printchar (out, *string);
   ++pc;
}
for ( ; width > 0; --width) {
   printchar (out, padchar);
   ++pc;
}

return pc;
}

/* the following should be enough for 32 bit int */
#define PRINT_BUF_LEN 12

static int printi(char **out, int i, int b, int sg, int width, int pad, int letbase)
{
char print_buf[PRINT_BUF_LEN];
register char *s;
register int t, neg = 0, pc = 0;
register unsigned int u = i;

if (i == 0) {
   print_buf[0] = '0';
   print_buf[1] = '\0';
   return prints (out, print_buf, width, pad);
}

if (sg && b == 10 && i < 0) {
   neg = 1;
   u = -i;
}

s = print_buf + PRINT_BUF_LEN-1;
*s = '\0';

while (u) {
   t = u % b;
   if( t >= 10 )
      t += letbase - '0' - 10;
   *--s = t + '0';
   u /= b;
}

if (neg) {
   if( width && (pad & PAD_ZERO) ) {
      printchar (out, '-');
      ++pc;
      --width;
   }
   else {
      *--s = '-';
   }
}

return pc + prints (out, s, width, pad);
}

static int print(char **out, int *varg)
{
register int width, pad;
register int pc = 0;
register char *format = (char *)(*varg++);
char scr[2];

for (; *format != 0; ++format) {
   if (*format == '%') {
      ++format;
      width = pad = 0;
      if (*format == '\0') break;
      if (*format == '%') goto out;
      if (*format == '-') {
         ++format;
         pad = PAD_RIGHT;
      }
      while (*format == '0') {
         ++format;
         pad |= PAD_ZERO;
      }
      for ( ; *format >= '0' && *format <= '9'; ++format) {
         width *= 10;
         width += *format - '0';
      }
      if( *format == 's' ) {
         register char *s = *((char **)varg++);
         pc += prints (out, s?s:"(null)", width, pad);
         continue;
      }
      if( *format == 'd' ) {
         pc += printi (out, *varg++, 10, 1, width, pad, 'a');
         continue;
      }
      if( *format == 'x' ) {
         pc += printi (out, *varg++, 16, 0, width, pad, 'a');
         continue;
      }
      if( *format == 'X' ) {
         pc += printi (out, *varg++, 16, 0, width, pad, 'A');
         continue;
      }
      if( *format == 'u' ) {
         pc += printi (out, *varg++, 10, 0, width, pad, 'a');
         continue;
      }
      if( *format == 'c' ) {
         /* char are converted to int then pushed on the stack */
         scr[0] = *varg++;
         scr[1] = '\0';
         pc += prints (out, scr, width, pad);
         continue;
      }
   }
   else {
   out:
      printchar (out, *format);
      ++pc;
   }
}
if (out) **out = '\0';
return pc;
}

/* assuming sizeof(void *) == sizeof(int) */

int printf(const char *format, ...)
{
register int *varg = (int *)(&format);
return print(0, varg);
}

int sprintf(char *out, const char *format, ...)
{
register int *varg = (int *)(&format);
return print(&out, varg);
}

#ifdef TEST_PRINTF
int main(void)
{
char *ptr = "Hello world!";
char *np = 0;
int i = 5;
unsigned int bs = sizeof(int)*8;
int mi;
char buf[80];

mi = (1 << (bs-1)) + 1;
printf("%s\n", ptr);
printf("printf test\n");
printf("%s is null pointer\n", np);
printf("%d = 5\n", i);
printf("%d = - max int\n", mi);
printf("char %c = 'a'\n", 'a');
printf("hex %x = ff\n", 0xff);
printf("hex %02x = 00\n", 0);
printf("signed %d = unsigned %u = hex %x\n", -3, -3, -3);
printf("%d %s(s)%", 0, "message");
printf("\n");
printf("%d %s(s) with %%\n", 0, "message");
sprintf(buf, "justif: \"%-10s\"\n", "left"); printf("%s", buf);
sprintf(buf, "justif: \"%10s\"\n", "right"); printf("%s", buf);
sprintf(buf, " 3: %04d zero padded\n", 3); printf("%s", buf);
sprintf(buf, " 3: %-4d left justif.\n", 3); printf("%s", buf);
sprintf(buf, " 3: %4d right justif.\n", 3); printf("%s", buf);
sprintf(buf, "-3: %04d zero padded\n", -3); printf("%s", buf);
sprintf(buf, "-3: %-4d left justif.\n", -3); printf("%s", buf);
sprintf(buf, "-3: %4d right justif.\n", -3); printf("%s", buf);

return 0;
}

/*
* if you compile this file with
* gcc -Wall $(YOUR_C_OPTIONS) -DTEST_PRINTF -c printf.c
* you will get a normal warning:
* printf.c:214: warning: spurious trailing `%' in format
* this line is testing an invalid % at the end of the format string.
*
* this should display (on 32bit int machine) :
*
* Hello world!
* printf test
* (null) is null pointer
* 5 = 5
* -2147483647 = - max int
* char a = 'a'
* hex ff = ff
* hex 00 = 00
* signed -3 = unsigned 4294967293 = hex fffffffd
* 0 message(s)
* 0 message(s) with %
* justif: "left "
* justif: " right"
* 3: 0003 zero padded
* 3: 3 left justif.
* 3: 3 right justif.
* -3: -003 zero padded
* -3: -3 left justif.
* -3: -3 right justif.
*/

#endif

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muggins

Joined: 20 Jan 2006
Posts: 6660
Location: lisbon

Posted: Sat 13 Aug 2011, 18:41 Post subject:

I got it to compile by commenting out lines 25, 195 & 260.

(By adding // to start of those respective lines)

muggins

Joined: 20 Jan 2006
Posts: 6660
Location: lisbon

Posted: Sat 13 Aug 2011, 18:47 Post subject:

Whoops, should be 25, 194 & 259.

Code:

//#define putchar(c) outbyte(c)
...
...
...
//#ifdef TEST_PRINTF
...
...
...
//#endif

sc0ttman

Joined: 16 Sep 2009
Posts: 2174
Location: UK

Posted: Sun 14 Aug 2011, 08:28 Post subject:

Great, I'll try that... How did you know to do that?
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muggins

Joined: 20 Jan 2006
Posts: 6660
Location: lisbon

Posted: Sun 14 Aug 2011, 22:50 Post subject:

Combination of some c progging, last century, some c++ this century, bit of google, reading the devs comments, and process of elimination.

sc0ttman

Joined: 16 Sep 2009
Posts: 2174
Location: UK

Posted: Wed 24 Aug 2011, 15:27 Post subject:

muggins wrote:

Combination of some c progging, last century, some c++ this century, bit of google, reading the devs comments, and process of elimination.

Just to update, muggins, you're great - it worked!
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