Cannot allocate memory for a structure

Question

I'm trying to write a program to compress/extract file by static HUFFMAN algorithm. I've already done my code, when I test with file .txt, everything is okay. But when I test with another file (ex: mp3, docx, etc), the compiler warns the error:"invalid null pointer". detail picture

After a moment later, I find out the line that made the error, but I cannot understand why this line is wrong: ".exe has triggered a breakpoint." detail picture

Here are my structure and function:

struct BITCODE
{
char *bit;
int size;
};
BITCode **bitTable;



#define MAX_UNSIGNED_CHAR 256
#define MAX 10
bool Allocate(int size, bool isCompress)
  {
//allocate hufftree
huffTree = new HUFFNode*[size];
if (huffTree == NULL)
    return false;

for (int i = 0; i < size; i++)
{
    huffTree[i] = new HUFFNode[MAX_NODE];
    if (huffTree[i] == NULL)
        return false;
}
//allocate frequency and bittable
freq = new long*[size];
if (freq == NULL)
    return false;

if (isCompress == true)
{
    bitTable = new BITCode*[size];
    if (bitTable == NULL)
        return false;
}
for (int i = 0; i < size; i++)
{
    freq[i] = new long[MAX_UNSIGNED_CHAR];
    if (freq[i] == NULL)
        return false;

    if (isCompress == true)
    {
        bitTable[i] = new BITCode[MAX_UNSIGNED_CHAR];
        if (bitTable[i] == NULL)
            return false;
    }
    for (int j = 0; j < MAX_UNSIGNED_CHAR; j++)
        freq[i][j] = 0;
}
}

void createBit_Table(int nRoot, int num)
{
for (int i = 0; i < MAX_UNSIGNED_CHAR; i++)
{
    bitTable[num][i].size = 0;
    bitTable[num][i].bit = NULL;
}
char bit[MAX];
int size = 0;
processHuffTree(nRoot, bit, 0,num);
}

void processHuffTree(int nNode,char bit[], int size,int num)
{
if (nNode == -1) //If it's a NULL tree
    return;
//process node leaf
if (huffTree[num][nNode].left == -1 && huffTree[num][nNode].right == -1)
{
    bitTable[num][nNode].bit = new char[size + 1]; //CAUSE ERROR
    bitTable[num][nNode].size = size;

    for (int i = 0; i < bitTable[num][nNode].size; i++)
        bitTable[num][nNode].bit[i] = bit[i];

    bitTable[num][nNode].bit[size] = '\0';

}
else
{
    //turn left
    bit[size] = '0';
    processHuffTree(huffTree[num][nNode].left, bit, size + 1,num);

    //turn right
    bit[size] = '1';
    processHuffTree(huffTree[num][nNode].right, bit, size + 1, num);
}
}

Please Do Not Use Screen Shots To Provide *Text*. Copypaste text into your question. — alk, Dec 10 '17 at 15:53
@Minh Please read [here](https://stackoverflow.com/questions/46991224/are-there-any-valid-use-cases-to-use-new-and-delete-raw-pointers-or-c-style-arr) thoroughly before asking further. — user0042, Dec 10 '17 at 16:02
Does the code you do *not* show us properly initialise `bitTable` to actually point to valid memory? — alk, Dec 10 '17 at 16:03

iBug · Answer 1 · 2017-12-10T16:19:20.867

0

The first part contains a fatal error (and I doubt it compiles):

struct BITCODE
{
    char *bit;
    int size;
}
BITCode **bitTable;

You're mixing up capitalization and structure definition. You need a semicolon to indicate end of structure:

    int size;
}; // a semicolon
BITCODE bitTable; // CAPITALIZATION!

Then, you didn't allocate any memory for bitTable. It is expected that you should have done it.

// somewhere in the beginning:
bitTable = new BITCODE*[MAX];
// inside createBit_Table()
bitTable[num] = new BITCODE[MAX_UNSIGNED_CHAR];

edited Dec 10 '17 at 16:19

answered Dec 10 '17 at 16:11

iBug

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I've allocated memory for bitTable – Minh Dec 10 '17 at 16:18
@Minh See the first part. – iBug Dec 10 '17 at 16:18
@PaulOgilvie It's C++ not C. – iBug Dec 10 '17 at 16:27
I see...in C++ the `struct` namespace and the `typedef` namespace are the same. It compiles. Apologies. – Paul Ogilvie Dec 10 '17 at 16:31

Cannot allocate memory for a structure

1 Answers1