Can't find what's causing access violation in array - c++

Question

!!!I have to stick with these functions as I'm not allowed to use any different!!!
A little explanation what I need to do: user input a search directory, then if nothing was found an error message pops up. If something is found, I create an array of one row because at least one file was found and it saves the name of found file. Then if FindNextFIle finds anything I add one row to existing array and this new row saves new found file name.
First output is direct output from the function and the second one is test output of the array to be sure that it worked correctly. Yet it doesn't work saying that memory access is violated so I can't work further.
There's probably 2 reasons why it's not working correctly:
Incorrect add of new row
incorrect print array function
Here's the main():
system("chcp 1251");
drtctrAr drctr;
drctr = createDAr();
WIN32_FIND_DATA FindFileData;
HANDLE hf;
hf = FindFirstFile(drctr.str, &FindFileData);
while (hf == INVALID_HANDLE_VALUE)
{
printf("Error opening files or no files found!\n Try changing the search directory or correct your input!\n");
return 1;
break;
}
StringArray fileNames;
int len;
fileNames.str = (wchar_t**)malloc(sizeof(wchar_t*) * fileNames.rows);
len = wcslen(FindFileData.cFileName)+1;
fileNames.sym = (wchar_t*)malloc(sizeof(wchar_t) * len);
wcscpy_s(fileNames.sym, len, FindFileData.cFileName);
while (FindNextFile(hf, &FindFileData) != 0)
{
printf("Found file: %ls", FindFileData.cFileName);
printf("\n");
fileNames.rows++;
fileNames.str = (wchar_t**)realloc(fileNames.str, sizeof(wchar_t*) * (fileNames.rows));
int len = wcslen(FindFileData.cFileName) + 1;
fileNames.str[fileNames.rows-1] = (wchar_t*)malloc(sizeof(wchar_t) * len);
wcscpy_s(fileNames.str[fileNames.rows-1], len, FindFileData.cFileName);
}
FindClose(hf);
freeDAr(drctr);
printSA(fileNames);
filterSA(fileNames);
freeSA(fileNames);
system("pause");
return 0;
And this is the print function in separate .cpp:
void printSA(StringArray arr)
{
printf("...........................\n");
for (int i = 0; i < arr.rows; i++)
{
for(int j=0;j<arr.sym[i];j++)
printf("Current file: %ls", arr.str[i][j]);
printf("\n");
}
}
And the array struct itself, forgot to add it:
struct StringArray
{
wchar_t** str = NULL;
wchar_t* sym = NULL;
int rows = 1;
};
I mentioned both probable reasons sadly it doesn't mean that these are the correct guess, something at the very start of allocating the array may be wrong

Answer 1

fileNames.str = (wchar_t**)malloc(sizeof(wchar_t*) * fileNames.rows);
len = wcslen(FindFileData.cFileName)+1;
fileNames.sym = (wchar_t*)malloc(sizeof(wchar_t) * len);
wcscpy_s(fileNames.sym, len, FindFileData.cFileName);
This issue exists in above lines. You allocate memory for str but you don't allocate memory for *str / str[0] which is type of wchar_t*. Then you copy file name to fileNames.sym instead of fileNames.str[0], so you don't find the error at first place. Then if second file is found, you allocate memory for fileNames.str[1] and copy the file name to it. This part is correct.
So the access violation excepion happens when you try to access the content of fileNames.str[0] because it is non-allocated memory. If you print fileNames.str[1], it will success.
The following is modified version based on your presented code. It works for me. You can have a try.
#include <stdio.h>
#include <windows.h>
typedef struct StringArray
{
wchar_t** str;
int rows;
}StringArray;
void printSA(StringArray arr)
{
printf("...........................\n");
for (int i = 0; i < arr.rows; i++)
{
printf("Current file: %ls", arr.str[i]);
printf("\n");
}
}
int main()
{
system("chcp 1251");
WIN32_FIND_DATA FindFileData;
HANDLE hf;
hf = FindFirstFile(L"D:\\*.txt", &FindFileData);
while (hf == INVALID_HANDLE_VALUE)
{
printf("Error opening files or no files found!\n Try changing the search directory or correct your input!\n");
return 1;
break;
}
StringArray fileNames;
fileNames.rows = 1;
int len;
fileNames.str = (wchar_t**)malloc(sizeof(wchar_t*) * fileNames.rows);
len = wcslen(FindFileData.cFileName) + 1;
fileNames.str[fileNames.rows - 1] = (wchar_t*)malloc(sizeof(wchar_t) * len);
wcscpy_s(fileNames.str[fileNames.rows - 1], len, FindFileData.cFileName);
while (FindNextFile(hf, &FindFileData) != 0)
{
printf("Found file: %ls", FindFileData.cFileName);
printf("\n");
fileNames.rows++;
fileNames.str = (wchar_t**)realloc(fileNames.str, sizeof(wchar_t*) * (fileNames.rows));
int len = wcslen(FindFileData.cFileName) + 1;
fileNames.str[fileNames.rows - 1] = (wchar_t*)malloc(sizeof(wchar_t) * len);
wcscpy_s(fileNames.str[fileNames.rows - 1], len, FindFileData.cFileName);
}
FindClose(hf);
printSA(fileNames);
// TODO: Free pointers
// ...
system("pause");
return 0;
}