Strcat issues when concatenating

Question

Hi for some reason Strcat does not like the value property within my structure. I'm not sure why. Here is my structure code:

typedef struct TrieSearchTree{
char value;
struct DynamicList* children; 
};

and here is my method:

void PrintDynamicListContents(struct DynamicList* dynamicList, char* word)
{
    struct dynamicListNode* currentRecord;
    struct TrieSearchTree* trieSearchTree;
    struct dynamicListNode* nextRecord = dynamicList->head;

    while(nextRecord != NULL)
    {
        currentRecord = nextRecord;
        nextRecord = currentRecord->next;
        trieSearchTree = currentRecord->entity;

        if (trieSearchTree != NULL)
        {
            if (trieSearchTree->value != WORD_END_CHAR)
            {
                char c[CHAR_LENGTH] = "";
                strcat_s(c, CHAR_LENGTH, word);
                strcat_s(c, CHAR_LENGTH, trieSearchTree->value);
                PrintDynamicListContents(currentRecord, c);
            }
            else
            {
                printf("%s", word);
            }
        }
    }
}

Here is the error message:

Proof that the value from the structure returns something (the 'l' character)

I've been trying to get strcat working for hours and I can't get it to work even reading the online tutorials. All help appreciated.

Answer 1

The strcat_s function expects a char * , specifically a pointer to a null terminated string, as the third argument. You're passing in a single char . Your compiler should have warned you about this.

That character is being interpreted as a pointer and being dereferenced. This invokes undefined behavior , which in this case manifests in a crash.

If you want to append a single character to a string, you need to add it and a new null terminator manually.

char c[CHAR_LENGTH] = "";
strcat_s(c, CHAR_LENGTH, word);
c[strlen(c) + 1] = '\0';
c[strlen(c)] = trieSearchTree->value;