C string arrays

Question

I just wrote a line splitting function:

typedef enum {
    strspl_allocation_error = 1
} strspl_error;


int strspl(const char *string, const char separator, char ***result) {

    const int stringLength = strlen(string);
    int lastSplit = 0;
    int numberOfComponents = 1;

    // Compute the number of components
    for (int i = 0; i <= stringLength; i++) {
        if (string[i] == separator)
            numberOfComponents++;
    }

    // Allocate space to hold pointers to each component
    *result = (char **) malloc(numberOfComponents * sizeof(char *));
    if (result == NULL)
        return strspl_allocation_error;

    numberOfComponents = 0;

    for (int i = 0; i <= stringLength; i++) {
        char c = string[i];
        if (c == separator || i == stringLength) {

            const int componentLength = i - lastSplit;

            // Allocate space to hold the component
            char *component = (char *) malloc(componentLength * sizeof(char));
            if (component == NULL)
                return strspl_allocation_error;

            // Copy the characters from the string into the component
            for (int j = 0; j < componentLength; j++)
                component[j] = string[lastSplit + j];
            component[componentLength] = '\0';

            // Put the component into the array
            *result[numberOfComponents] = component;

            lastSplit = i + 1;
            numberOfComponents++;
        }
    }

    return numberOfComponents;
}

Example:

char **result;
int r = strspl("aaaBcBddddeeBk", 'B', result);

for (int i = 0; i < r; i++)
    printf("component: %s\n", result[i]);

should be displayed:

component: aaa
component: c
component: ddddee
component: k

But when I run it, it either crashes or returns garbage values. I do not understand where I am making a mistake ...

Update: here, I hope the error-free version:

int strspl(const char *string, const char separator, char ***results) {

    const char *separatorString = (char[]){separator, '\0'};
    int numberOfComponents = 0;
    int stringLength = strlen(string);

    int lastCharacterWasSeparator = 1;

    // Compute the number of components
    for (int i = 0; i < stringLength; i++) {
        if (string[i] != separator) {
            if (lastCharacterWasSeparator)
                numberOfComponents++;
            lastCharacterWasSeparator = 0;
        }
        else
            lastCharacterWasSeparator = 1;
    }

    // Allocate space to hold pointers to components
    *results = malloc(numberOfComponents * sizeof(**results));

    char *stringCopy = strdup(string); // A reference to the copy of the string to modify it and to free() it later.
    char *strptr = stringCopy; // This will be used to iterate through the string.
    int componentLength = 0;
    int component = 0;

    while (component < numberOfComponents) {

        // Move to the startpoint of the next component.
        while (componentLength == 0) {
            componentLength = strcspn(strptr, separatorString);

            // Break out the while loop if we found an actual component.
            if (componentLength != 0)
                break;

            // If we found two adjacent separators, we just "silently" move over them.
            strptr += componentLength + 1;
        }

        // Replace the terminating separator character with a NULL character.
        strptr[componentLength] = '\0';

        // Copy the new component into the array.
        (*results)[component++] = strdup(strptr);

        // Move the string pointer ahead so we can work on the next component.
        strptr += componentLength + 1;

        componentLength = 0;
    }

    // Free the copy of the string.
    free(stringCopy);

    return numberOfComponents;
}

Answer 1

Sorry, everything we suggested you do to fix it together and broke again! From the source code, make the following settings:

• Function signatures should be char ***resultinstead char **result.
• Array allocation should be *result = malloc(...)instead result = malloc(...).
• , component[componentLength] = '\0'; (*result)[numberOfComponents] = component; ( , char***).
• , , : strspl(..., &result); strspl(..., result);

---

, C/++... , :

, :

Address     -  Data        -  Description
0x99887760  -  0xbaadbeef  -  caller-result variable (uninitialized garbage)

: strspl(..., result);, (0xbaadbeef) strspl:

Address     -  Data        -  Description
0x99887750  -  0xbaadbeef  -  strspl-result variable (copy of uninitialized garbage)
...
0x99887760  -  0xbaadbeef  -  caller-result variable (uninitialized garbage)

, result = malloc(...) strspl-result, :

Address     -  Data        -  Description
0x99887750  -  0x01000100  -  strspl-result variable (new array)
...
0x99887760  -  0xbaadbeef  -  caller-result variable (uninitialized garbage)

, .

---

: strspl(..., &result); :

Address     -  Data        -  Description
0x99887750  -  0x99887760  -  strspl-result variable (pointer to the caller result)
...
0x99887760  -  0xbaadbeef  -  caller-result variable (uninitialized garbage)

, result = malloc(...), :

Address     -  Data        -  Description
0x99887750  -  0x01000100  -  strspl-result variable (new array)
...
0x99887760  -  0xbaadbeef  -  caller-result variable (uninitialized garbage)

, , .

---

*result = malloc(...), :

Address     -  Data        -  Description
0x99887750  -  0x99887760  -  strspl-result variable (pointer to the caller result)
...
0x99887760  -  0x01000100  -  caller-result variable (new array)

, , malloc 'd.

---

, . , , ( char*** not char**).

, , !:-P

Answer 2

• for(int i = 0; i < stringLength; i++), ​​ .
• char *, char *** result *result = (char**) malloc(...).
• , component result
• , strdup strcpy

Answer 3

• result
• " " malloc, NUL
• , char **result, .
• malloc() C. . ,

. .

Update

strspl()

int strspl(const char *string, const int separator, char ***result)
{
    int len, n=1, i=0;
    char *strptr = *copy = strdup(string);

    while(*strptr++) {
        if (*strptr == separator){ n++; }
    }

    *result = malloc(n * sizeof(**result));

    //Reset Pointer to Beginning of string
    strptr = copy;

    while(len = strcspn(strptr, (char []){separator, '\0'})) {
        strptr[len] = '\0';
        (*result)[i++] = strdup(strptr);
        strptr += len + 1;
    }

    free(copy);
    return n;
}

component: aaa
component: c
component: ddddee
component: k