我在理解指针在特定情况下如何工作时遇到了一些麻烦。我的困惑的细节概述如下。
我创建了一个名为 buffer 的 8 字节字符串的字符数组，我试图使用 fread() 将文件中的 8 个字节加载到这个 8 字节字符串数组的元素之一中。
我位于 /c/file.txt 的文件的内容很简单： TESTTEST
我希望程序将 TESTTEST 加载到缓冲区 [1] 而不是值 ijklmnop 中，仅此而已。
我知道缓冲区实际上是一个指针数组，在这种情况下，它只是三个连续的内存地址，其中包含三个不以空值结尾的连续字节数组的第一个元素的地址。
我将其可视化为一行中的 24 个内存地址，其中包含 ABCDEFGHijklmnopQRSTUVWX 的二进制值，末尾没有 \0。
buffer[0]的地址指向一个指向A的地址，buffer[1]的地址指向一个指向i的地址，buffer[2]的地址指向一个指向Q的地址。
我看到 &buffer[1] 的 fread() 将 8 个字节读入存储在缓冲区 [1] 中的地址的位置。
我在这个 fread() 上尝试过各种尝试，使用 &buffer+1、buffer+1、(buffer+1) 等等，但大多数都给了我分段错误；&buffer[1] 似乎几乎可以满足我的要求。
尝试执行 printf("buffer[1] as %%s is %s\n", buffer[1]); 在 fclose() 之前接近尾声时出现分段错误。
我接近理解，但有些事情不太正确，我没有掌握一些我需要的基本概念。
我不确定终止 (buffer+1)[8] 是否溢出到缓冲区 [2] 的第一个地址，或者有什么影响。
总的来说，我有点困惑，任何帮助将不胜感激。
谢谢！
这是我的整个程序：
#include <stdio.h>
#include <string.h>
int main()
{
FILE *fp;
char c[] = "OFFONOFF";
char *buffer[] = {"ABCDEFGH", "ijklmnop", "QRSTUVWX"};
char *t;
printf("the value in file /c/file.txt is TESTTEST, only those 8 bytes\n");
printf("the ls listing for /c/file.txt shows 9, I am not sure where the other character comes from\n");
printf("the value as %%s of buffer[0] is %s\n", buffer[0]);
printf("the value as %%s of buffer[1] is %s\n", buffer[1]);
printf("the value as %%s of buffer[2] is %s\n", buffer[2]);
printf("the sizeof(buffer[2]) is %d\n", sizeof(buffer[2]));
fp = fopen("/c/file.txt", "r");
fseek(fp, SEEK_SET, 0);
printf("the value as %%c of buffer[1][3] is %c\n", buffer[1][3]);
printf("the memory address as %%p for buffer+1 is %p\n", buffer+1);
fread(&buffer[1], strlen(c), 1, fp);
/* I am attempting to terminate the fread into &buffer[1] with a \0, removing this doesn't change much */
(buffer+1)[8] = "\0";
printf("the memory addreses below are all in %%p format\n");
printf("the memory address of buffer is %p\n", buffer);
printf("memory address of buffer[1] is %p\n", buffer[1]);
printf("memory address of &buffer is %p\n", &buffer);
printf("memory address of &buffer+1 is %p\n", &buffer+1);
printf("memory address of &buffer[1] is %p\n", &buffer[1]);
printf("memory address of buffer is %p\n", buffer);
printf("memory address of buffer[15] is %p\n", buffer[15]);
printf("memory address of buffer+15 is %p\n", buffer+15);
printf("memory address of *(buffer+1) is %p\n", *(buffer+1));
printf("the sizeof(buffer[0]) is %d\n", sizeof(buffer[0]));
printf("the sizeof(*(buffer+1)) is %d\n", sizeof(*(buffer+1)));
printf("the sizeof(buffer) is %d\n", sizeof(buffer));
printf("the value of *(buffer+0) as %%s is %s\n", *(buffer+0));
printf("the value of *buffer, the first element of the array of strings, as %%s is %s\n", *buffer);
printf("the value of buffer+1, the first element of the array of strings, as %%s is %s\n", buffer+1);
printf("buffer[0] as %%s is %s\n", buffer[0]);
printf("buffer+1 as %%s is %s\n", buffer+1);
printf("buffer[2] as %%s is %s\n", buffer[2]);
printf("buffer is %s\n", buffer+1);
printf("sizeof(*buffer) is %d\n", sizeof(*buffer));
fclose(fp);
return(0);
}
这是确切的输出：
the value in file /c/file.txt is TESTTEST, only those 8 bytes
the ls listing for /c/file.txt shows 9, I am not sure where the other character comes from
the value as %s of buffer[0] is ABCDEFGH
the value as %s of buffer[1] is ijklmnop
the value as %s of buffer[2] is QRSTUVWX
the sizeof(buffer[2]) is 8
the value as %c of buffer[1][3] is l
the memory address as %p for buffer+1 is 0x7ffff7b23a28
the memory addreses below are all in %p format
the memory address of buffer is 0x7ffff7b23a20
memory address of buffer[1] is 0x5453455454534554
memory address of &buffer is 0x7ffff7b23a20
memory address of &buffer+1 is 0x7ffff7b23a38
memory address of &buffer[1] is 0x7ffff7b23a28
memory address of buffer is 0x7ffff7b23a20
memory address of buffer[15] is 0x400674
memory address of buffer+15 is 0x7ffff7b23a98
memory address of *(buffer+1) is 0x5453455454534554
the sizeof(buffer[0]) is 8
the sizeof(*(buffer+1)) is 8
the sizeof(buffer) is 24
the value of *(buffer+0) as %s is ABCDEFGH
the value of *buffer, the first element of the array of strings, as %s is ABCDEFGH
the value of buffer+1, the first element of the array of strings, as %s is TESTTEST
@
buffer[0] as %s is ABCDEFGH
buffer+1 as %s is TESTTEST
@
buffer[2] as %s is QRSTUVWX
buffer is TESTTEST
@