本文对比了malloc()和calloc()两种动态内存分配函数的区别。malloc()仅分配内存但不初始化，而calloc()不仅分配内存还会将所有位设置为零。此外，calloc()返回的是元素数组的指针。
Both the malloc() and the calloc() functions are used to allocate dynamic memory. Each operates slightly different from the other.
Both the malloc() and the calloc() functions are used to allocate dynamic memory. Each operates slightly different from the other. malloc() takes a size and returns a pointer to a chunk of memory at least that big:
void *malloc( size_t size );
calloc() takes a number of elements, and the size of each, and returns a pointer to a chunk of memory
at least big enough to hold them all:
void *calloc( size_t numElements, size_t sizeOfElement );
There are one major difference and one minor difference between the two functions. The major difference is that malloc() doesn't initialize the allocated memory. The first time malloc() gives you a particular chunk of memory, the memory might be full of zeros. If memory has been allocated, freed, and reallocated, it probably has whatever junk was left in it.
*****
That means, unfortunately, that a program might run in simple cases (when memory is never reallocated) but break when used harder (and when memory is reused).
*****
calloc() fills the allocated memory with all zero bits. That means that anything there you are going to use as a char or an int of any length, signed or unsigned, is guaranteed to be zero. Anything you are going to use as a pointer is set to all zero bits.
That is usually a null pointer, but it is not guaranteed.Anything you are going to use as a float or double is set to all zero bits; that is a floating-point zero on some types of machines, but not on all.
The minor difference between the two is that calloc() returns an array of objects; malloc() returns one object. Some people use calloc() to make clear that they want an array.
簡單的來說 就是
Malloc申請一大塊內存 不管你用它來做什么 也不易定慧把它清零
Calloc申請一大塊內存 把它按數組處理 而且會幫你把它的每個bit置零
Both the malloc() and the calloc() functions are used to allocate dynamic memory. Each operates slightly different from the other. malloc() takes a size and returns a pointer to a chunk of memory at least that big:
void *malloc( size_t size );
calloc() takes a number of elements, and the size of each, and returns a pointer to a chunk of memory
at least big enough to hold them all:
void *calloc( size_t numElements, size_t sizeOfElement );
There are one major difference and one minor difference between the two functions. The major difference is that malloc() doesn't initialize the allocated memory. The first time malloc() gives you a particular chunk of memory, the memory might be full of zeros. If memory has been allocated, freed, and reallocated, it probably has whatever junk was left in it.
*****
That means, unfortunately, that a program might run in simple cases (when memory is never reallocated) but break when used harder (and when memory is reused).
*****
calloc() fills the allocated memory with all zero bits. That means that anything there you are going to use as a char or an int of any length, signed or unsigned, is guaranteed to be zero. Anything you are going to use as a pointer is set to all zero bits.
That is usually a null pointer, but it is not guaranteed.Anything you are going to use as a float or double is set to all zero bits; that is a floating-point zero on some types of machines, but not on all.
The minor difference between the two is that calloc() returns an array of objects; malloc() returns one object. Some people use calloc() to make clear that they want an array.
簡單的來說 就是
Malloc申請一大塊內存 不管你用它來做什么 也不易定慧把它清零
Calloc申請一大塊內存 把它按數組處理 而且會幫你把它的每個bit置零
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