What's wrong in this C program..? - c

Question

struct bucket
{
int nStrings; //No. of Strings in a Bucket.
char strings[MAXSTRINGS][MAXWORDLENGTH]; // A bucket row can contain maximum 9 strings of max string length 10.
};//buck[TOTBUCKETS];
void lexSorting(char array[][10], int lenArray, int symb) //symb - symbol, sorting based on character symbols.
{
int i, j;
int bucketNo;
int tBuckNStrings;
bucket buck[TOTBUCKETS];
for(i=0; i<lenArray; i++)
{
bucketNo = array[i][symb] - 'a'; // Find Bucket No. in which the string is to be placed.
tBuckNStrings = buck[bucketNo].nStrings; // temp variable for storing nStrings var in bucket structure.
strcpy(buck[bucketNo].strings[tBuckNStrings],array[i]); // Store the string in its bucket.
buck[bucketNo].nStrings = ++tBuckNStrings; //Increment the nStrings value of the bucket.
}
// lexSorting(array, lenArray, ++symb);
printf("****** %d ******\n", symb);
for(i=0; i<TOTBUCKETS; i++)
{
printf("%c = ", i+'a');
for(j=0; j<buck[i].nStrings; j++)
printf("%s ",buck[i].strings[j]);
printf("\n");
}
}
int main()
{
char array[][10] = {"able","aback","a","abet","acid","yawn","yard","yarn","year","yoke"};
int lenArray = 10;
int i;
printf("Strings: ");
for(i=0; i<lenArray; i++)
printf("%s ",array[i]);
printf("\n");
lexSorting(array, lenArray, 0);
}
Well here is the complete code, that I am trying. since its been a long time since i have touched upon C programming, so somewhere i am making mistake in structure declaration.
The problem goes here:-
1) I have declared a structure above and its object as array(buck[]).
2) Now when I declare this object array along with the structure, it works fine.. I have commented this thing right now.
3) But when I declare this object array inside the function.. because ultimately i have to declare inside function( as i need to build a recursive program, where objects will be created in very recursive call) then the program is throwing segmentation fault.
Expected Output
> [others#centos htdocs]$ ./a.out
> Strings: able aback a abet acid yawn
> yard yarn year yoke
> ****** 0 ******
> a = able aback a abet acid
> b =
> c
> .
> .
> y = yawn yard yarnyear yoke
> z =
Actual Output
[others#centos htdocs]$ ./a.out
Strings: able aback a abet acid yawn yard yarn year yoke
Segmentation fault
I have no idea, what difference I made in this. Kindly help.
Thanks.

Answer 1

What's wrong with your program is that it doesn't contain a main() function hence it won't link.
Beyond that, you should always do the following when asking questions here:
Provide a complete, minimal code sample that demonstrates the problem.
Detail the expected behaviour.
Detail the actual behaviour.
In fact, when I add the line:
int main (void) { return 0; }
it compiles and links fine.
That means it's almost certainly a run-time error you're experiencing hence we need the main() to figure out what you're doing wrong.
Using my psychic debugging skills, an important difference between declaring it at file scope and block scope is that the file-scope version will be initialised to zeros.
That means all the structure fields will be effectively zero (for the count) and empty strings (for the strings). With block scope, those counts and strings will be uninitialised.
The fact that you're using TOBUCKETS to print the structure out probably means you're trying to print out one of those uninitialised strings.
I think what's probably happening is that the nStrings field contains a garbage value when you start the processing. You should probably initialise it to zero manually (with a loop) and see if that fixes your problem. Put this after the declaration of buck in your sort function:
for (i = 0; i < TOTBUCKETS; i++)
buck[i].nStrings = 0;
Right. It turns out that was the problem. When I fix up the errors in your latest code, I get the segmentation violation as well but, when I add that section above, it works fine:
#include <stdio.h>
#include <string.h>
#define MAXSTRINGS 9
#define MAXWORDLENGTH 10
#define TOTBUCKETS 26
struct bucket
{
int nStrings;
char strings[MAXSTRINGS][MAXWORDLENGTH];
};
void lexSorting(char array[][10], int lenArray, int symb)
{
int i, j;
int bucketNo;
int tBuckNStrings;
struct bucket buck[TOTBUCKETS];
for(i=0; i<TOTBUCKETS; i++) buck[i].nStrings = 0;
for(i=0; i<lenArray; i++)
{
bucketNo = array[i][symb] - 'a';
tBuckNStrings = buck[bucketNo].nStrings;
strcpy(buck[bucketNo].strings[tBuckNStrings],array[i]);
buck[bucketNo].nStrings = ++tBuckNStrings;
}
printf("****** %d ******\n", symb);
for(i=0; i<TOTBUCKETS; i++)
{
printf("%c = ", i+'a');
for(j=0; j<buck[i].nStrings; j++)
printf("%s ",buck[i].strings[j]);
printf("\n");
}
}
int main()
{
char array[][10] = {"able","aback","a","abet","acid",
"yawn","yard","yarn","year","yoke"};
int lenArray = 10;
int i;
printf("Strings: ");
for(i=0; i<lenArray; i++)
printf("%s ",array[i]);
printf("\n");
lexSorting(array, lenArray, 0);
}
The output of that was:
Strings: able aback a abet acid yawn yard yarn year yoke
****** 0 ******
a = able aback a abet acid
b =
c =
d =
e =
f =
g =
h =
i =
j =
k =
l =
m =
n =
o =
p =
q =
r =
s =
t =
u =
v =
w =
x =
y = yawn yard yarn year yoke
z =

Answer 2

keyword struct is not required when you create objects for it.