realloc的错误：释放对象

Question

不正确的校验和我试着写了从标准输入读取数据代码：

size_t bufSize = 1024; 
unsigned char *msg = NULL; 
size_t msgBytes = 0; 
size_t inputMsgBufCount = 0; 
unsigned char inputBuffer[bufSize]; 
size_t bytesRead = 0; 
unsigned char *tmp = NULL; 

if ((msg = (unsigned char *)malloc(sizeof(unsigned char) * bufSize)) == NULL) 
    exit(EXIT_FAILURE); 
bytesRead = fread(msg, sizeof(unsigned char) * bufSize, 1, stdin); 
inputMsgBufCount++; 

while (bytesRead) { 
    printf("iteration: %lu\n", inputMsgBufCount); 
    if ((tmp = (unsigned char *)realloc(msg, (inputMsgBufCount * bufSize) + bufSize)) != NULL) { 
     printf("reallocated\n"); 
     msg = tmp; 
     inputMsgBufCount++; 
    } 
    else { 
     printf("Ran out of memory\n"); 
     free(msg); 
    } 
    bytesRead = fread(inputBuffer, sizeof(unsigned char) * bufSize, 1, stdin); 
    memmove((msg + (inputMsgBufCount * bufSize)), inputBuffer, bufSize); 
} 

free(msg); 

msgBytes = (inputMsgBufCount * bufSize); 

gettimeofday(&end, NULL); 
printf("%10.6lf [MB/s]\n", (msgBytes/(1<<20))/((end.tv_sec - start.tv_sec) + (end.tv_usec - start.tv_usec) * 1.0e-6f)); 

但运行它像这样经过： 〜＃DD如果= /开发/零BS = 1024 count = 8 | ./test 我有这样的错误：

 
iteration: 1 
reallocated 
iteration: 2 
reallocated 
iteration: 3 
reallocated 
iteration: 4 
reallocated 
iteration: 5 
reallocated 
iteration: 6 
reallocated 
iteration: 7 
test(11450) malloc: *** error for object 0x100804008: incorrect checksum for freed object - object was probably modified after being freed. 
*** set a breakpoint in malloc_error_break to debug 
Abort trap 

谁能帮我请。

Answer 1

inputMsgBufCount应该增加后您复制您的消息缓冲区中的数据。你在第一次阅读时就做对了，但对于其他所有内容，在你重新分配之后立即增加它。如果你遵循它的值，当你进入循环时它是1。您重新分配到2*bufSize，并增加inputMsgBufCount，这使得它2.然后您读取数据，并将其复制到msg+2*bufSize。这会破坏你的缓冲区。你应该复制到msg+bufSize。简单地延迟增加变量直到复制数据。

另一方面，您可以安全地使用memcpy()来复制数据。 msg和inputBuffer将永远不会重叠。其实你应该完全摆脱inputBuffer，并直接读取到msg在正确的偏移量。