晚上被这个内存扩展崩溃的问题折腾的有点崩溃，当答案揭晓的那一刻，恍然大悟，原来如此简单。
练习题目：输入一个字符串，根据字母进行排序，说白了就是一个简单的冒泡
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h> #define BUF_LEN 100
#define COUNT 5 int main(void)
{
char buf[BUF_LEN];
size_t str_count = ;
size_t capacity = COUNT;
char **pS = calloc(capacity, sizeof(char*));
char **psTemp = NULL;
char *pTemp = NULL;
size_t str_len = ;
bool sorted = false; printf("Enter strings to be sorted, one per line. Press Enter to end:\n"); char *ptr = NULL; while(true)
{
ptr = fgets(buf, BUF_LEN, stdin);
if(!ptr)
{
printf("Error reading string.\n");
free(pS);
pS = NULL;
return ;
} if(*ptr == '\n')
break; if(str_count == capacity)
{
capacity += capacity/; if(!(psTemp = realloc(pS, capacity)))
return ;
pS = psTemp;
} str_len = strlen(buf) + ; if(!(pS[str_count] = malloc(str_len)))
return ;
strcpy(pS[str_count++], buf);
} while(!sorted)
{
sorted = true;
size_t i = ;
for(; i < str_count - ; i++)
{
if(strcmp(pS[i], pS[i+]) > )
{
sorted = false;
pTemp = pS[i];
pS[i] = pS[i+];
pS[i + ] = pTemp;
} }
} printf("Your input sorted in ascending sequence is:\n\n");
size_t i = ;
for(; i < str_count; i++)
{
printf("%s", pS[i]);
free(pS[i]);
pS[i] = NULL;
}
free(pS);
pS = NULL; return ;
}
上面标黄处，首先是通过calloc进行内存分配，初始是capacity的长度是5，接着判断当输入的字符串个数等于5了，那么就动态的扩展内存，继续按25%的速度增长。就是在扩展这里，一直报错：
*** Error in `./program714.out': realloc(): invalid next size: 0x0000000002365010 ***
======= Backtrace: =========
/lib64/libc.so.(+0x7f5d4)[0x7f476bff35d4]
/lib64/libc.so.(+0x83bd8)[0x7f476bff7bd8]
/lib64/libc.so.(realloc+0x1d2)[0x7f476bff9832]
./program714.out[0x4008ea]
/lib64/libc.so.(__libc_start_main+0xf5)[0x7f476bf963d5]
./program714.out[0x400729]
======= Memory map: ========
- r-xp fd: /home/wlf/practice/program714.out
- r--p fd: /home/wlf/practice/program714.out
- rw-p fd: /home/wlf/practice/program714.out
- rw-p : [heap]
7f4764000000-7f4764021000 rw-p :
7f4764021000-7f4768000000 ---p :
7f476bd5e000-7f476bd73000 r-xp fd: /usr/lib64/libgcc_s-4.8.-.so.
7f476bd73000-7f476bf72000 ---p fd: /usr/lib64/libgcc_s-4.8.-.so.
7f476bf72000-7f476bf73000 r--p fd: /usr/lib64/libgcc_s-4.8.-.so.
7f476bf73000-7f476bf74000 rw-p fd: /usr/lib64/libgcc_s-4.8.-.so.
7f476bf74000-7f476c136000 r-xp fd: /usr/lib64/libc-2.17.so
7f476c136000-7f476c336000 ---p 001c2000 fd: /usr/lib64/libc-2.17.so
7f476c336000-7f476c33a000 r--p 001c2000 fd: /usr/lib64/libc-2.17.so
7f476c33a000-7f476c33c000 rw-p 001c6000 fd: /usr/lib64/libc-2.17.so
7f476c33c000-7f476c341000 rw-p :
7f476c341000-7f476c363000 r-xp fd: /usr/lib64/ld-2.17.so
7f476c557000-7f476c55a000 rw-p :
7f476c55e000-7f476c562000 rw-p :
7f476c562000-7f476c563000 r--p fd: /usr/lib64/ld-2.17.so
7f476c563000-7f476c564000 rw-p fd: /usr/lib64/ld-2.17.so
7f476c564000-7f476c565000 rw-p :
7ffde3137000-7ffde3158000 rw-p : [stack]
7ffde31c5000-7ffde31c7000 r-xp : [vdso]
ffffffffff600000-ffffffffff601000 r-xp : [vsyscall]
Aborted
代码看来看去发现没毛病，唯一能怀疑的地方就是内存扩展的那一行，经过几番折腾，发现只要一到需要增长调用realloc就报错，最后回去看calloc，只能一拍大腿骂娘了，字节计算的类型不对啊，一个是按char*（相当于二维数组pS[][]中的子数组pS[]）来计算字节，一个是按字符（char）来计算字节，得到的内存大小必然不同啊。把realloc的第二个参数加上这个就解决了：
if(!(psTemp = realloc(pS, capacity*sizeof(char*))))
编码需谨慎，差之毫厘，谬之千里，一点小小的bug都能让程序崩溃。
