我編譯一次文件,並使用相同的輸出運行它,並且我僅在大約20-30%的時間內出現分段錯誤。我只是給我的教授發了郵件,但她永遠都在。我真的不知道爲什麼,特別是因爲錯誤不會一直髮生,但有時只有完全相同的a.out文件。我知道錯誤發生的位置,來自if(sDB [index] == 0)。隨機分割故障C++
感謝您的幫助,
請讓我知道如果需要更多的代碼來解決這個問題。
* SDB是在我的構造初始化指針數組:
*sDB = new HashElem[MAX];
結構:
struct Elem {
student *info;
Elem *next;
};
struct HashElem {
student *info;
HashElem *next;
};
的我的代碼片斷:
void studentsDB::push(student *std) {
Elem *e = new Elem;
e->info = std;
Elem *cur = head;
while(cur->next != 0)
cur = cur->next;
cur->next = e;
e->next = 0;
int index = std->hash();
HashElem *h = new HashElem;
h->info = std;;
if(sDB[index] == 0) { //<<< THIS LINE CAUSES THE ERROR
sDB[index] = h;
h->next = 0;
}
else {
HashElem *ha = sDB[index];
while(ha->next != 0) {
ha = ha->next;
}
ha->next = h;
}
size++;
}
散列():
int student::hash() {
int ret = 0;
string s = id;
for(int i = 0; i < s.length(); i++)
ret = 33 * ret + s[i];
return ret % MAX;
}
輸出:
bash-4.2$ g++ *.cpp
bash-4.2$ ./a.out students.dat courses.dat
begin
objects created
+++ Before the if statement +++
+++ 548 +++
Segmentation fault
bash-4.2$ ./a.out students.dat courses.dat
begin
objects created
+++ Before the if statement +++
+++ 548 +++
Segmentation fault
bash-4.2$ ./a.out students.dat courses.dat
begin
objects created
+++ Before the if statement +++
+++ 548 +++
+++ After +++
+++ Before the if statement +++
+++ 626 +++
+++ After +++
+++ Before the if statement +++
+++ 605 +++
+++ After +++
+++ Before the if statement +++
+++ 915 +++
+++ After +++
+++ Before the if statement +++
+++ 915 +++
printList
Flintstone, Fred 000-12SA 3 121314 12333 12116
Flintstone, Wilma 000-45SA 2 12332 12111
Glotz, Joe Q 901-9984 3 12332 12116 12111
Rubble, Barney 001-01SA 3 121314 12111 12116
CS001 1 12111 1 10 3 000-45SA 901-9984 001-01SA
CS515 2 121314 4 45 2 000-12SA 001-01SA
CH302 1 12116 5 15 3 000-12SA 901-9984 001-01SA
MA111 1 12333 4 15 1 000-12SA
PH999 1 12999 2 10 0000-12SA901-9984
PY000 3 12332 6 5 2 000-45SA 901-9984
bash-4.2$ ./a.out students.dat courses.dat
begin
objects created
+++ Before the if statement +++
+++ 548 +++
Segmentation fault
bash-4.2$ ./a.out students.dat courses.dat
begin
objects created
+++ Before the if statement +++
+++ 548 +++
Segmentation fault
bash-4.2$ ./a.out students.dat courses.dat
begin
objects created
+++ Before the if statement +++
+++ 548 +++
+++ After +++
+++ Before the if statement +++
+++ 626 +++
+++ After +++
+++ Before the if statement +++
+++ 605 +++
+++ After +++
+++ Before the if statement +++
+++ 915 +++
+++ After +++
+++ Before the if statement +++
+++ 915 +++
printList
Flintstone, Fred 000-12SA 3 121314 12333 12116
Flintstone, Wilma 000-45SA 2 12332 12111
Glotz, Joe Q 901-9984 3 12332 12116 12111
Rubble, Barney 001-01SA 3 121314 12111 12116
CS001 1 12111 1 10 3 000-45SA 901-9984 001-01SA
CS515 2 121314 4 45 2 000-12SA 001-01SA
CH302 1 12116 5 15 3 000-12SA 901-9984 001-01SA
MA111 1 12333 4 15 1 000-12SA
PH999 1 12999 2 10 0000-12SA901-9984
PY000 3 12332 6 5 2 000-45SA 901-9984
bash-4.2$ ./a.out students.dat courses.dat
begin
objects created
+++ Before the if statement +++
+++ 548 +++
+++ After +++
+++ Before the if statement +++
+++ 626 +++
+++ After +++
+++ Before the if statement +++
+++ 605 +++
+++ After +++
+++ Before the if statement +++
+++ 915 +++
Segmentation fault
GDB輸出:
Starting program: /home/csu/dtk24/cs515/prog11/a.out students.dat courses.dat
begin
objects created
+++ Before the if statement +++
+++ 548 +++
Program received signal SIGSEGV, Segmentation fault.
0x0804b2a0 in studentsDB::push (this=0xbffff78c, std=0x8054120)
at studentsDB.cpp:130
130 if(sDB[index] == 0) {
用valgrind運行它。 – 2012-04-22 23:45:46
你怎麼知道'std-> hash()'返回的散列值對'sDB'(即'MAX')的範圍有效? – 2012-04-22 23:46:17
散列函數的可能輸出是什麼?你有沒有檢查是否每次都分配了sDB?你可以發佈std-> hahs()的代碼嗎?前面的 – 2012-04-22 23:48:12