尝试通过指针数组从二维数组打印字符串时出现分段错误

Question

Edit:

So, for anyone having the same problem, it seems that despite initializing the array of pointers to NULL, the array still had some trash written in it. I fixed the segmentation by replacing the header of the last while statement(in function printer) with this:

while( (wordPtr[ctr] != NULL) && (ctr < MAX_WORDS) )

Original question:

The first function of the program is supposed to get some text and populate a two-dimensional array of strings with the words in the text, but each word has to appear only once. Then, it has to populate a two-dimensional array of pointers to strings with the addresses of the words in such a way that the second function can then use those pointers to reprint the text in the order it was originally.

The problem I am facing is that, while the array of strings seems to populate as it should, I face a segmentation fault error whenever I try to print the text using the array of pointers.

I think that the problem lies somewhere in the lines where I direct the pointer to the word, but other than that I can't find much.

I tried using gdb, but the result pointed to strlen.s, which is a function that I haven't used anywhere in the code.

Thanks in advance.

The code:

#include <stdio.h>
#include <ctype.h>
#include <string.h>


#define MAX_WORDS 6
#define MAX_WORD_LEN 10

void placer(char wordsArray[MAX_WORDS][MAX_WORD_LEN], char *ptr[MAX_WORDS][2]);
void printer(char *wordPtr[][2], int linelen);

int main (int argc, char *argv[]){
     char wordArray[MAX_WORDS][MAX_WORD_LEN] = {{ '\0' }};
     char *wordPtr[MAX_WORDS][2] = {{ NULL }};
     int linelen = 100;
     
     placer(wordArray, wordPtr); 
     printer(wordPtr, linelen);
     
     return 0;
}

void placer(char wordsArray[][MAX_WORD_LEN], char *ptr[][2]){
    
    int i, j, k, temp, w = 0, g = 0;
    char check[MAX_WORD_LEN] = {'\0'};
    for (i = 0; i < MAX_WORDS; i++) {
        
        scanf("%s", wordsArray[i]);
        
        //Converts to lowercase
        for (j = 0; j < MAX_WORD_LEN; j++) {
            if(isupper(wordsArray[i][j])) {
                wordsArray[i][j] = tolower(wordsArray[i][j]);
            }
        }
        
        //assigns to pointer array
        ptr[w][0] = &wordsArray[i][0];
        
        //Checks if word already exists in array
        for(k = 0; k < i; k++) {
            if(strcmp(wordsArray[i], wordsArray[k]) == 0) {
                //Directs pointer to the already existing instance of the word
                ptr[w][0] = &wordsArray[k][0];
                //replaces the word with \0
                for (g = 0; g < MAX_WORD_LEN; g++) {
                    wordsArray[i][g] = '\0';
                }
                i--;
                break;
            }
        }
        w++;
    }
    
    //prints from array of unique words
    printf("%s\n\n\n", &wordsArray[1][0]);
    for(temp = 0; temp < MAX_WORDS; temp++) {
        printf("%s\n", wordsArray[temp]);
    }
    
    printf("\n##\n");
}

void printer(char *wordPtr[][2], int linelen) {
    
    int ctr = 0, t;
        
    //prints using pointers
    while (wordPtr[ctr] != NULL) {
        printf("%s", *wordPtr[ctr]);
        ctr++;
    }
}

Answer 1

This is an excellent opportunity to learn to use a debugger . Your system almost surely provides a way to run the code in a way so you can single-step through the source code, view the value of variables at any point, place breakpoints, etc.

By doing so you can check what the program actually does versus what you expected it to do. Most problems of this type are very easily diagnosed by single stepping. Each debugger has (at least) a small learning curve but it is well worth the effort to learn the basics.