C/Development/Debug

Copy a file in debug mode

<source lang="cpp">

1. include <stdio.h>
2. include <stdlib.h>
3. define DEBUG

int main(int argc, char *argv[]) {

 FILE *from, *to;
 char ch;
 /* check number of command line arguments */
 if( argc != 3) {
   printf("Usage: copy <source> <destination>\n");
   exit(1);
 }
 /* open source file */
 if((from = fopen(argv[1], "rb"))==NULL) {
   printf("Cannot open source file.\n");
   exit(1);
 }
 /*open destination file */
 if((to = fopen (argv[2], "wb")) ==NULL) {
   printf("Cannot open destination file.\n");
   exit(1);
 }
 while(!feof(from)) {
   ch = fgetc(from);
   if(ferror(from)) {
     printf("Error reading source file.\n");
     exit(1);
   }
   if(!feof(from)) {
     fputc(ch, to);
   }
   if(ferror(to)) {
     printf("Error writing destination file.\n");
     exit(1);
   }
 }
 fclose(from);
 fclose(to);
 return 0;

}

      </source>

Copy a file in four debug level

<source lang="cpp">

1. include <stdio.h>
2. include <stdlib.h>

/* DEBUG levels:

         0: no debug
         1: display byte read from source file
         2. display byte written to destination file
         3: display bytes read and bytes written

• /

1. define DEBUG 2

int main(int argc, char *argv[]) {

 FILE *in, *out;
 unsigned char ch;
 /* see if correct number of command line arguments */
 if(argc!=4) {
   printf("Usage: code <in> <out> <key>");
   exit(1);
 }
 /* open input file */
 if((in = fopen(argv[1], "rb"))==NULL) {
   printf("Cannot open input file.\n");
   exit(1);
 }
 /* open output file */
 if((out = fopen(argv[2], "wb"))==NULL) {
   printf("Cannot open output file.\n");
   exit(1);
 }
 while(!feof(in)) {
   ch = fgetc(in);

1. if DEBUG == 1 || DEBUG == 3

   putchar(ch);

1. endif

   ch = *argv[3] ^ ch;

1. if DEBUG >= 2

   putchar(ch);

1. endif

   if(!feof(in)) fputc(ch, out);
 }
 fclose(in);
 fclose(out);
 return 0;

}

      </source>

Debugging using pre-processing directives

<source lang="cpp">

1. include <stdio.h>
2. include <stdlib.h>
3. define test
4. define testf

int sum(int, int); int product(int, int); int difference(int, int); int main() {

 int i = 0;
 int j = 0;
 int a = 10, b = 5;
 int result = 0;
 int (*pfun[3])(int, int);

 pfun[0] = sum;
 pfun[1] = product;
 pfun[2] = difference;
 for(i = 0 ; i < 3 ; i++)
 {
   j = i;
   #ifdef test
   printf("\nRandom number = %d", j );
   #endif
   result = pfun[j](a , b);
   printf("\nresult = %d", result );
 }
 result = pfun[1](pfun[0](a , b), pfun[2](a , b));
 printf("\n\nThe product of the sum and the difference = %d\n", result);

} int sum(int x, int y){

 #ifdef testf
 printf("\nFunction sum called.");
 #endif
 return x + y;

} int product( int x, int y ){

 #ifdef testf
 printf("\nFunction product called.");
 #endif
 return x * y;

} int difference(int x, int y){

 #ifdef testf
 printf("\nFunction difference called.");
 #endif
 return x - y;

}

      </source>