使用 qsort 出现段错误
我需要对字符数组进行排序，以便对其进行迭代并打印出唯一的数据点及其计数。该数组保存在链表节点内，我想使用 qsort 来执行此操作。不幸的是，我在该特定行遇到了段错误。
void printArray(Node_ptr node){
int count=0; //character count
char *temp= node->attributes; //duplicate attribute array
char cur; //current char
char *outputCat= emalloc(150); //concatenate counts to a single string
outputCat= "Attribute %d counts are: ";
qsort(&temp, lineCount, sizeof(char), compare); //sort the array
... more code
}
我从 man qsort 页面抄袭了比较方法
int compare(const void *a, const void *b){
return strcmp(*(char * const *) a, *(char * const *) b);
}
。在 DDD 中，qsort 行是触发段错误的行。本来以为是参数不准确，所以加了一些调试printf语句。 printf("%s", temp) 打印出 1000 个字符，这正是行数应有的值。每个字符都是 1 个字节，因此这里不需要 sizeof(char) 。
该行上 ddd 的错误报告是“
Program received signal SIGSEGV, Segmentation fault.
0xb7f8c498 in ?? () from /lib/libc.so.6
这是 qsort 的错误，还是我的代码有其他问题？”
I need to sort an array of characters in order to iterate over it and print out the unique data points and their count. This array is held inside a linked list node, and I want to use qsort to do this. Unfortunately, I'm getting a segfault right at that particular line.
void printArray(Node_ptr node){
int count=0; //character count
char *temp= node->attributes; //duplicate attribute array
char cur; //current char
char *outputCat= emalloc(150); //concatenate counts to a single string
outputCat= "Attribute %d counts are: ";
qsort(&temp, lineCount, sizeof(char), compare); //sort the array
... more code
}
I cribbed the compare method from the man qsort page
int compare(const void *a, const void *b){
return strcmp(*(char * const *) a, *(char * const *) b);
}
In DDD, the qsort line is the one that triggers the segfault. I originally thought it was due to inaccuracies in the parameters, so I put in some debugging printf statements. printf("%s", temp) prints out 1000 characters, which is exactly what linecount should be. Chars are 1 byte each, so no need for sizeof(char) here.
The error report from ddd on that line is
Program received signal SIGSEGV, Segmentation fault.
0xb7f8c498 in ?? () from /lib/libc.so.6
Is this qsort's fault, or something else with my code?
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这
应该是：
您不需要传递指针的地址！
qsort的第一个参数是一个指针，因此如果你向它传递一个指针，则不需要使用地址运算符，否则你将传递一个指向指针的指针，这不是在这种情况下你想要什么。This
Should be:
You do not need to pass the address of a pointer!
qsort's first argument is a pointer, so if you pass it a pointer, you do not need to use the address-of operator, else you're passing a pointer to a pointer, which is not what you want in this case.如果要对字符进行排序，qsort() 的第一个参数应该是字符指针，而不是指向字符指针的指针。 strcmp() 也是如此
另外：请添加结构节点的定义。
If you want to sort characters, the first argument to qsort() should be a character pointer, not a pointer to a character pointer. The same for the strcmp()
Also: please add the definition for struct node.