I have an array of strings defined like this:
char** arrNames;
Now I want to dynamically allocate a size to it. I have a function that receives the new size and the array above. It goes like this:
char** AddName(char** arrNames, int nNameCount)
{
char** arrTemp;
arrTemp = new char[nNameCount];
...
// And later I change the pointer of arrNames to arrTemp
}
Now this obviously doesn't work. So what should I be doing instead?
Thanks in advance.
If you want nNameCount strings, you need to allocate an array of arrays of chars (i.e an array of strings):
char** AddName(char** arrNames, int nNameCount)
{
char** arrTemp = new char *[nNameCount];
for (int i = 0; i < nNameCount; ++i) arrTemp[i] = new char[STRING_SIZE];
...
}
After this you can access each string with arrTemp[index]. Note that you still need to initialize each string.
Here is an working example of how to initialize Dynamic Array of Dynamic strings.
twoDStr = new char*[10];
twoDStr[0] = new char[10];
cin>>twoDStr[0];
cout<<twoDStr[0]<<endl;
// And later I change the pointer of arrNames to arrTemp
For this to work properly, you'd need arrNames to be a pointer to an array.
char** AddName(char*** arrNames, int nNameCount) {
//...
*arrNames = arrTemp;
}
Don't forget to free any previously allocated memory arrNames might refer to!
In C, functions for dynamically allocating memory are malloc(), calloc(), realloc() and free().
man malloc should give you more informations.
valloc is a legacy Posix thing, not standard C.
neweven if you happen to be (very unwisely IMO) using a C++ compiler to compile your C code. If you want to learn C++ then in real life don't usenewfor this either, use a vector. For the purposes of understanding how memory allocation works in C++ you could usenewfor this, but if you're supposed to be learning malloc/free for use in C, then you won't do so by using C++ new[]/delete[] instead ;-)