c - 为包含另一个struct数组的struct正确分配内存

Question

I want to allocate memory for a struct that contains an array of another struct named table . I detected that when assigning the pointers to the functions at the end, the variables in the linkedObjects array get corrupted so i think my handling of dynamic memory is wrong.

This is how i'm doing it now:

typedef struct Object {
    void *key;
    struct Object *top;
    struct Object *next;
} Object;

typedef struct Table{
    Object *linkedObjects;
    size_t size, originalSize;
    HashFcn hfun;
    PrintFcn pfun;
    ComparisonFcn fcomp;
} Table;

TableP CreateTable(size_t tableSize, HashFcn hfun, PrintFcn pfun, ComparisonFcn fcomp)
{
    int i;
    struct Table *table = malloc(sizeof(table));
    if (table==NULL)
    {
        ReportError(MEM_OUT);
        return NULL;
    }
    table->linkedObjects = NULL;
    table->linkedObjects  = malloc(tableSize * sizeof(Object));

    for(i=0;i<tableSize;i++)
    {

        table->linkedObjects[i].next = malloc( MAX_IN_LIST*sizeof(Object) );
        table->linkedObjects[i].top = malloc( MAX_IN_LIST*sizeof(Object) );
        table->linkedObjects[i].key = NULL;
        table->linkedObjects[i].top->key = NULL;
        table->linkedObjects[i].next->key = NULL;

        if (table->linkedObjects[i].next == NULL)
        {
            ReportError(MEM_OUT);
            return NULL;
        }
    }

    table->size = tableSize;
    table->originalSize = tableSize;
    table->hfun = hfun;
    table->pfun = pfun;
    table->fcomp = fcomp;
    return table;
}

Edit: I edited the function code to reflect the answers:

TableP CreateTable(size_t tableSize, HashFcn hfun, PrintFcn pfun, ComparisonFcn fcomp)
{
    int i;
    struct Table *table = malloc(sizeof(table));
    if (table==NULL)
    {
        ReportError(MEM_OUT);
        return NULL;
    }
    table->linkedObjects = NULL;
    table->linkedObjects  = malloc(tableSize * sizeof(Object));

    if (table->linkedObjects == NULL)
    {
        ReportError(MEM_OUT);
        return NULL;
    }

    for(i=0;i<tableSize;i++)
    {
        table->linkedObjects[i].next = NULL;
        table->linkedObjects[i].top = NULL;
        table->linkedObjects[i].key = NULL;
    }

    table->size = tableSize;
    table->originalSize = tableSize;
    table->hfun = hfun;
    table->pfun = pfun;
    table->fcomp = fcomp;
    //printf("%p\n", table->hfun);
    return table;
}

but still when i get to the point of the assignments at the end, the table->linkedObjects[0].key that is null and value is 0x0 get's overrun to a value 0x8048cc0 . This occurs when this line is executed:

table->originalSize = tableSize;

Another Edit: Confirmed that it happens randomly in the last calls (not only in the line above):

table->size = tableSize;
table->originalSize = tableSize;
table->hfun = hfun;
table->pfun = pfun;
table->fcomp = fcomp;

Answer 1

struct Table *table = malloc(sizeof(table));

should be

struct Table *table = malloc(sizeof(Table));

I sometimes love C.

`

Answer 2

As usual, get rid of the habit of using type names under sizeof . This is how your memory allocations should have looked

Table *table = malloc(sizeof *table);
...
table->linkedObjects = malloc(tableSize * sizeof *table->linkedObjects);

That would also fix the "typo" error in the first allocation.

Answer 3

table->linkedObjects[i].next = malloc( MAX_IN_LIST*sizeof(Object) );
table->linkedObjects[i].top = malloc( MAX_IN_LIST*sizeof(Object) );

This doesn't seem to make sense. When I see next or top with collections, I expect a single pointer to one Object (to the next item in the collection or to the first item in the collection).

Did you mean to do the following:

for(i=0;i < (tableSize-1);i++)
{
    table->linkedObjects[i].top = table->linkedObjects[0];
    table->linkedObjects[i].next = table->linkedObjects[i+1];
    table->linkedObjects[i].key = NULL;
}

This will allocate memory for each Object , and sets up the pointers afterwards.