malloc()没有分配足够的空间

Question

你好，这是我的问题

FILE *sourcefile;
if ((sourcefile = fopen(argv[1],"r")) == NULL)  //Opens File
{
    printf("Error: Could not open %sn",argv[1]);
    return 0;
}
fseek(sourcefile, 0 , SEEK_END);  // Sets file pointer at the end of the file
unsigned int fSize = ftell(sourcefile); // Determines file size by the position of file pointer
fseek(sourcefile, 0 , SEEK_SET); // Sets file pointer at the start of the file
char *buffer = (char *) malloc(fSize); 
if (buffer == NULL)
{
    printf("Error: Not enough system memoryn");
    return 0;
}
printf("%dn",sizeof(buffer));
printf("%dn",fSile);
fread (buffer,1,fSize,sourcefile);
fclose (sourcefile);

我的代码只是打开一个文件并将其内容加载到内存中。问题是，当我使用

时

char *buffer = (char *) malloc(fSize)

只分配4个字节而不是文件的完整大小(即打开带有小句子的简单TXT时为25字节)。当我在最后打印buffer和fSize的尺寸时，我分别得到4和25，所以fSize是正确的。知道为什么会这样吗?

谢谢,

Answer 1

sizeof(buffer) 在32位平台上应为4字节。它是一个指向malloc分配的缓冲区的指针。没有办法查询缓冲区的大小

Answer 2

sizeof(buffer)是指针的大小或32位(4字节)。

Answer 3

这可能就是你想要达到的效果。

#include <stdio.h>
#include <stdlib.h>
int  main(int argc, char *argv[])
{
    FILE *sourcefile;
    if ((sourcefile = fopen(argv[1],"r")) == NULL)  //Opens File
    {
        printf("Error: Could not open %sn",argv[1]);
        eturn 0;
    }
    fseek(sourcefile, 0 , SEEK_END);  // Sets file pointer at the end of the file
    unsigned long fSize = ftell(sourcefile); 
    fseek(sourcefile, 0 , SEEK_SET); // Sets file pointer at the start of the file
    fSize -= ftell(sourcefile);  /*This determines file size  */
    char *buffer = (char *) malloc(fSize); 
    if (buffer == NULL)
    {
    printf("Error: Not enough system memoryn");
    return 0;
    }
    printf("%ldn",sizeof(buffer)); 
    printf("%ldn",fSize);
    fread (buffer,1,fSize,sourcefile);
    fclose (sourcefile);
    return 1;
}