我有以下代码,但出现以下错误
error C2036: 'void *' : unknown size
error C2440: 'static_cast' : cannot convert from 'void *' to 'size_t'
在线
void *addr = static_cast <void*> (static_cast <size_t> (mem + bytesAlreadyAllocated));
我的问题是为什么会出现上述错误以及如何消除这些错误?
感谢您的帮助。
class MemoryChunk {
public:
MemoryChunk (MemoryChunk *nextChunk, size_t chunkSize);
~MemoryChunk() {delete mem; }
inline void *alloc (size_t size);
inline void free (void* someElement);
// Pointer to next memory chunk on the list.
MemoryChunk *nextMemChunk() {return next;}
// How much space do we have left on this memory chunk?
size_t spaceAvailable() { return chunkSize - bytesAlreadyAllocated; }
// this is the default size of a single memory chunk.
enum { DEFAULT_CHUNK_SIZE = 4096 };
private:
// The MemoryChunk class is a cleaner version of NextOnFreeList. It separates the next pointer from
// the actual memory used for the allocated object. It uses explicit next and mem pointers, with no
// need for casting.
MemoryChunk *next;
void *mem;
// The size of a single memory chunk.
size_t chunkSize;
// This many bytes already allocated on the current memory chunk.
size_t bytesAlreadyAllocated;
};
MemoryChunk::MemoryChunk(MemoryChunk *nextChunk, size_t reqSize) {
chunkSize = (reqSize > DEFAULT_CHUNK_SIZE) ? reqSize : DEFAULT_CHUNK_SIZE;
next = nextChunk;
bytesAlreadyAllocated = 0;
mem = new char [chunkSize];
}
void* MemoryChunk :: alloc (size_t requestSize) {
void *addr = static_cast <void*> (static_cast <size_t> (mem + bytesAlreadyAllocated));
bytesAlreadyAllocated += requestSize;
return addr;
}
inline void MemoryChunk :: free (void *doomed) {}
最佳答案
表达式:
static_cast <size_t> (mem + bytesAlreadyAllocated)
使用未定义大小的类型 (void
) 应用偏移量。由于 void
没有大小,程序的格式不正确。
char*
是适合您在此场景中使用的指针。例如:
`char* mem;`
// and
char* addr(mem + bytesAlreadyAllocated);
更新
所以在下面的程序中:
#include <iostream>
int main(int argc, const char* argv[]) {
const int array[3] = {-1, 0, 1};
std::cout << *(array + 0) << ", "
<< *(array + 1) << ", " << *(array + 2) << "\n";
return 0;
}
输出为 -1, 0, 1
。根据数组元素的大小和类型应用元素偏移量。使用 void
-- 大小不正确。
关于c++ - VS 2010 中 C++ 中的 static_cast 无法从 void* 转换为 size_t 错误,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/10381558/