bsearch 和 struct（自定义类型）

我有一个像这样的数组：

typedef struct INSTR
{
    char* str;
    int  argc;
} INSTR;
const static INSTR instructions[] = { {"blue",1}, {"green",2} };

然后我尝试做一个bsearch，但我得到了Segmentation fault信息：

int comp(const void *a, const void *b)
{
    const INSTR *aa = (INSTR*)a;
    const INSTR *bb = (INSTR*)b; 
    // if I "return 0;" here i get no error.
    return strcmp(aa->str, bb->str);
}

.

char *str = get_string(src_buff, size);
bsearch(str, instructions,
        sizeof(instructions) / sizeof(instructions[0]),
        sizeof(instructions[0]), comp);

The comp()函数不正确。来自here http://www.cplusplus.com/reference/clibrary/cstdlib/bsearch/:

比较器 比较两个元素的函数。该函数应遵循以下原型：

int comparator ( const void * pkey, const void * pelem );

The function must accept two parameters: the first one pointing to the
key object, and the second one to an element of the array, both
type-casted as void*. The function should cast the parameters back to
some data type and compare them.

你的第一个论点comp() is a const char*, not a INSTR*.

改成：

int comp(const void *a, const void *b)
{
    const INSTR *bb = (INSTR*)b; 
    return strcmp((const char*)a, bb->str);
}

或者，更改key成为一个INSTR*代替const char*.