我在这里遇到了一个真正奇怪的问题。当我使用手动打印语句来输出int * primesArr的值时,它工作(看似),但如果我尝试使用for循环执行此操作,它将失败。我通过gdb运行它,发现它正好在我将数组中的下一个单元格设置为值'k'的地方崩溃,这只发生在数字为素数时。第一次迭代成功(即2设置为primesArr [0]),然后在尝试增加数组时尝试程序Segfaults。但是这只有在使用for循环时才会发生。当我创建单独的打印语句时,我的程序按预期工作。我不知道如何/为什么我访问使用for循环时未被占用的内存。我确定我在某处执行过一些业余错误,这可能与我如何传递指针有关......但我无法确定它的确切根源。我会很感激任何帮助,并提前感谢您。指针分割错误
#include<stdio.h>
int genPrimes(int seed, int *test){
int inNumPrimes=0;
for(int k=0; k<=seed; k++){//k is number being checked for primeness
int cnt=0;
for(int i=1; i<=k; i++){//'i' is num 'k' is divided by
if(k%i == 0){
cnt++;
if(cnt > 2){
break;
}
}else{
}
}
if(cnt == 2){
printf("%i IS PRIME\n",k);
*test=k;
test++;//according to gdb, the problem is somewhere between here
inNumPrimes++;//and here. I'd wager I messed up my pointer somehow
}
//printf("%i\n",k);
}
return inNumPrimes;
}
int main(){
int outNumPrimes=0;
int *primesArr;
int n = 0;
n=20;
outNumPrimes=genPrimes(n, primesArr);
printf("Congratulations! There are %i Prime Numbers.\n",outNumPrimes);
//If you print using this for loop, the SEGFAULT occurs. Note that it does not matter how high the limit is; its been set to many values other than 5. It will eventually be set to 'outNumPrimes'
//for(int a=0; a<5; a++){
//printf("%i\n",primesArr[a]);
//}
//If you print the array elements individually, the correct value--a prime number--is printed. No SEGFAULT.
printf("%i\n",primesArr[0]);
printf("%i\n",primesArr[1]);
printf("%i\n",primesArr[2]);
printf("%i\n",primesArr[3]);
printf("%i\n",primesArr[4]);
printf("%i\n",primesArr[5]);
printf("%i\n",primesArr[6]);
printf("%i\n",primesArr[7]);
//
return 0;
}
输出,带手动声明:
$ ./a.out
2 IS PRIME
3 IS PRIME
5 IS PRIME
7 IS PRIME
11 IS PRIME
13 IS PRIME
17 IS PRIME
19 IS PRIME
Congratulations! There are 8 Prime Numbers.
2
3
5
7
11
13
17
19
与
现在for循环:
$ ./a.out
2 IS PRIME
Segmentation fault
谢谢您的额外建议,他们很感激。按照您和其他人的建议,我可以通过显式初始化缓冲存储器来修复程序。谢谢! – shelladept