0

Consider the following abstracted code that reads some bytes from a file:

typedef struct A{
int size;
char * dataArray;
}A

A load(char* filename, int inSize)
{
    A newA;
    newA.size = inSize;
    FILE *filePtr;
    filePtr = fopen(filename,"rb");

    char buff[1];
    int i = 0;

    newA.dataArray = ( char*)malloc(sizeof(char) * newA.size);
    for (i = 0; i < newA.size; i++)
    {
        fread(buff, sizeof(char), 1, filePtr);
        newA.dataArray[i] = buff[0];
    }

    char* copyOfDataArray = (char*)malloc(sizeof(char) * newA.size);

    for (i = 0; i < newA.size; i++)
    {
        fread(buff, sizeof(char), 1, filePtr);
        copyOfDataArray[i] = newA.dataArray[i];
    }

    newA.dataArray = copyOfDataArray;
    return newA
}

void Initialize()
{
    A first = load("file1", 100);
    A second = load("file2", 20);
}

Both calls to function load return the expected result (data array has the same bytes as the file). Variables first and second are never used again.

However after a couple of hundreds lines of code the program always crashes with:

*malloc.c:2451: sYSMALLOC: Assertion '(old_top == (..... failed.*

The crash always occurs on the same line of code, but that line has nothing to do with variables first, second or even with struct A whatsoever.

My question is: is my way of instancing and loading 'first' and 'second' wrong? Can it cause some kind of memory leak / memory overflow that crashes the program long after the load function has finished?

Bonus: The crash does not occur if I only load "file1", as soon as i load both "file1" and "file2" the crash reappears.

Sorry for the long question.

4

2 回答 2

1

你那里有内存泄漏。在分配新内存之前，您必须释放之前在 newA.dataArray 中分配的内存。

正如 Joachim 所说，读取操作非常耗时，您应该以块为单位读取数据以最小化开销。

此外，您必须关闭文件描述符，否则它们将很快耗尽。

于 2014-09-05T12:53:43.533 回答
0

其他人已经给出的代码有很多问题。请检查以下

typedef struct A{
int size;
char * dataArray;
}A

A load(char* filename, int inSize)
{
    A newA;
    newA.size = inSize;
    FILE *filePtr = NULL ; //Use NULL 
    char buff[1]; //Size of buffer is only 1 ,If needed increase that to copy more at a time
    int i = 0;

filePtr = fopen(filename,"rb");    
//Try to check for the filePtr == NULL or not

newA.dataArray = ( char*)malloc(sizeof(char) * newA.size);
//Same checking should be done here

for (i = 0; i < size; i++) //What is size 
{
    fread(buff, sizeof(char), 1, filePtr);
    newA.dataArray[i] = char[0]; //What is char[0]
}
//instead this you can read the bytes in a single call, use that.
// fread(buff, sizeof(char), <size to read >, filePtr);

char* copyOfDataArray = (char*)malloc(sizeof(char) * newA.size);

for (i = 0; i < size; i++)
{
    fread(buff, sizeof(char), 1, filePtr);
    copyOfDataArray[i] = newA.dataArray[i];
}

//why reading again once you done above.
newA.dataArray = copyOfDataArray;

return newA; //Please check: How you can return a auto variable.
}
void Initialize()
{
    A first = load("file1", 100);
    A second = load("file2", 20);
}
于 2014-09-05T13:07:16.313 回答