我正在编写这个程序，将方形，立方体，4的倍数，5的倍数打印成2维数组。 我总是遇到分段错误错误。你能帮忙解释一下发生了什么吗？ 该程序不会打印2D阵列的所有元素。它在第4或第6行之后以分段错误结束。
#include<stdio.h>
#include<stdlib.h>
void numbers(int ***arr,int nrows,int ncols);
void square(int ***arr,int nrows,int ncols);
void cube(int ***arr,int nrows,int ncols);
void multiples_of_4(int ***arr,int nrows,int ncols);
void multiples_of_5(int ***arr,int nrows,int ncols);
void free_our_ptr(int ***arr,int nrows,int ncols);
int main(void)
{
int i=0;
int nrows = 0;
int ncols = 0;
int menu_choice = 0;
int **arr;
printf("\nGet number of rows : ");
scanf("%d",&nrows);
if(nrows > 10)
{
printf("\nRows should be less than 10 ");
exit(0);
}
printf("\nGet number of columns : ");
scanf("%d",&ncols);
if(ncols > 10)
{
printf("\nColumns should be less than 10 ");
exit(0);
}
/******* Dynamic memory allocation for array ***********/
arr = (int **) malloc ( nrows * sizeof(int));
for(i=0;i<nrows;i++)
{
arr[i] = (int *) malloc ( ncols * sizeof(int));
}
/********************************************************/
printf("\nThese are your choices : ");
printf("\nFill with Integers ---------------- 1");
printf("\nFill with Squares ---------------- 2");
printf("\nFill with Cubes ------------------- 3");
printf("\nFill with Multiples of 4 ---------- 4");
printf("\nFill with Multiples of 5 ---------- 5");
printf("\n\nEnter your choice : ");
scanf("%d",&menu_choice);
switch(menu_choice)
{
case 1:
numbers(&arr,nrows,ncols);
break;
case 2:
square(&arr,nrows,ncols);
break;
case 3:
cube(&arr,nrows,ncols);
break;
case 4:
multiples_of_4(&arr,nrows,ncols);
break;
case 5:
multiples_of_5(&arr,nrows,ncols);
break;
default :
printf("\nInvalid Choice, exiting program");
free(arr);
exit(0);
}
exit(0);
}
void numbers(int ***array,int nrows,int ncols)
{
int i=0;
int j=0;
int number = 1;
int **arr;
arr = *array;
for(i=0;i<nrows;i++)
{
printf("\n");
for(j=0;j<ncols;j++)
{
arr[i][j] = number;
printf("%d\t",arr[i][j]);
number++;
}
}
free_our_ptr(&arr,nrows,ncols);
}
void square(int ***array,int nrows,int ncols)
{
int i=0;
int j=0;
int number = 1;
int **arr;
arr = *array;
for(i=0;i<nrows;i++)
{
printf("\n");
for(j=0;j<ncols;j++)
{
arr[i][j] = number * number;
printf("%d\t",arr[i][j]);
++number;
}
}
free_our_ptr(&arr,nrows,ncols);
}
void cube(int ***array,int nrows,int ncols)
{
int i=0;
int j=0;
int number = 1;
int **arr;
arr = *array;
for(i=0;i<nrows;i++)
{
printf("\n");
for(j=0;j<ncols;j++)
{
arr[i][j] = number * number * number;
printf("%d\t",arr[i][j]);
number++;
}
}
free_our_ptr(&arr,nrows,ncols);
}
void multiples_of_4(int ***array,int nrows,int ncols)
{
int i=0;
int j=0;
int number = 1;
int **arr;
arr = *array;
for(i=0;i<nrows;i++)
{
printf("\n");
for(j=0;j<ncols;j++)
{
arr[i][j] = number * 4;
printf("%d\t",arr[i][j]);
number++;
}
}
free_our_ptr(&arr,nrows,ncols);
}
void multiples_of_5(int ***array,int nrows,int ncols)
{
int i=0;
int j=0;
int number = 1;
int **arr;
arr = *array;
for(i=0;i<nrows;i++)
{
printf("\n");
for(j=0;j<ncols;j++)
{
arr[i][j] = number * 5;
printf("%d\t",arr[i][j]);
number++;
}
}
free_our_ptr(&arr,nrows,ncols);
}
void free_our_ptr(int ***arr,int nrows,int ncols)
{
int i;
for(i=0;i<nrows;i++)
{
free(arr[i]);
}
free(arr);
}
我尝试了这些建议，完全删除了free_our_ptr（）函数并释放了main（）本身的内存。在ubuntu linux gcc上，它给出了分段错误错误。但是，在Visual Studio-Windows7上，运行完全正常，在任何测试用例中都没有错误。以下是修改后的代码。
#include<stdlib.h>
void numbers(int ***arr,int nrows,int ncols);
void square(int ***arr,int nrows,int ncols);
void cube(int ***arr,int nrows,int ncols);
void multiples_of_4(int ***arr,int nrows,int ncols);
void multiples_of_5(int ***arr,int nrows,int ncols);
int main(void)
{
int i=0;
int nrows = 0;
int ncols = 0;
int menu_choice = 0;
int **arr;
printf("\nGet number of rows : ");
scanf_s("%d",&nrows);
if(nrows > 10)
{
printf("\nRows should be less than 10 ");
exit(0);
}
printf("\nGet number of columns : ");
scanf_s("%d",&ncols);
if(ncols > 10)
{
printf("\nColumns should be less than 10 ");
exit(0);
}
printf("\nNumber of rows = %d",nrows);
printf("\nNumber of cols = %d",ncols);
/******* Dynamic memory allocation for array ***********/
arr = (int **) malloc ( nrows * sizeof(int));
for(i=0;i<nrows;i++)
{
arr[i] = (int *) malloc ( ncols * sizeof(int));
}
/********************************************************/
printf("\nThese are your choices : ");
printf("\nFill with Integers ---------------- 1");
printf("\nFill with Squares ---------------- 2");
printf("\nFill with Cubes ------------------- 3");
printf("\nFill with Multiples of 4 ---------- 4");
printf("\nFill with Multiples of 5 ---------- 5");
printf("\n\nEnter your choice : ");
scanf_s("%d",&menu_choice);
switch(menu_choice)
{
case 1:
numbers(&arr,nrows,ncols);
break;
case 2:
square(&arr,nrows,ncols);
break;
case 3:
cube(&arr,nrows,ncols);
break;
case 4:
multiples_of_4(&arr,nrows,ncols);
break;
case 5:
multiples_of_5(&arr,nrows,ncols);
break;
default :
printf("\nInvalid Choice, exiting program");
free(arr);
exit(0);
}
free(arr);
exit(0);
}
void numbers(int ***array,int num_rows,int num_columns)
{
int i=0;
int j=0;
int number = 1;
int **arr;
int r1 = num_rows;
int c1 = num_columns;
arr = *array;
printf("\nNumber of rows = %d",r1);
printf("\nNumber of cols = %d",c1);
for(i=0;i<r1;i++)
{
printf("\n");
for(j=0;j<c1;j++)
{
arr[i][j] = number;
printf("%d\t",arr[i][j]);
number++;
}
}
}
void square(int ***array,int num_rows,int num_columns)
{
int i=0;
int j=0;
int number = 1;
int **arr;
int r2 = num_rows;
int c2 = num_columns;
arr = *array;
printf("\nNumber of rows = %d",r2);
printf("\nNumber of cols = %d",c2);
for(i=0;i<r2;i++)
{
printf("\n");
for(j=0;j<c2;j++)
{
arr[i][j] = number * number;
printf("%d\t",arr[i][j]);
++number;
}
}
}
void cube(int ***array,int num_rows,int num_columns)
{
int i=0;
int j=0;
int number = 1;
int **arr;
int r3 = num_rows;
int c3 = num_columns;
arr = *array;
printf("\nNumber of rows = %d",r3);
printf("\nNumber of cols = %d",c3);
for(i=0;i<r3;i++)
{
printf("\n");
for(j=0;j<c3;j++)
{
arr[i][j] = number * number * number;
printf("%d\t",arr[i][j]);
number++;
}
}
}
void multiples_of_4(int ***array,int num_rows,int num_columns)
{
int i=0;
int j=0;
int number = 1;
int **arr;
int r4 = num_rows;
int c4 = num_columns;
arr = *array;
printf("\nNumber of rows = %d",r4);
printf("\nNumber of cols = %d",c4);
for(i=0;i<r4;i++)
{
printf("\n");
for(j=0;j<c4;j++)
{
arr[i][j] = number * 4;
printf("%d\t",arr[i][j]);
number++;
}
}
}
void multiples_of_5(int ***array,int num_rows,int num_columns)
{
int i=0;
int j=0;
int number = 1;
int **arr;
int r5 = num_rows;
int c5 = num_columns;
arr = *array;
printf("\nNumber of rows = %d",r5);
printf("\nNumber of cols = %d",c5);
for(i=0;i<r5;i++)
{
printf("\n");
for(j=0;j<c5;j++)
{
arr[i][j] = number * 5;
printf("%d\t",arr[i][j]);
number++;
}
}
}
答案 0 :(得分：1)
arr = (int **) malloc ( nrows * sizeof(int));
不对。它必须是
arr = (int **) malloc ( nrows * sizeof(int*));
^^^^ an array of pointers to int.
第一个为nrows int s分配足够的空间
第二个为nrows int* s分配足够的空间。
此外，由于您使用的是C而不是C ++，因此请不要使用malloc的返回值。见Do I cast the result of malloc?
只需使用：
arr = malloc ( nrows * sizeof(int*));
函数free_our_ptr也不对。
void free_our_ptr(int ***arr,int nrows,int ncols)
{
int i;
for(i=0;i<nrows;i++)
{
free(arr[i]);
^^^^ Not right
}
free(arr);
^^^ Not right.
}
我建议修复它是将界面更改为：
void free_our_ptr(int **arr, int nrows, int ncols);
^^^^ Use int**, not int***.
然后，函数中的代码将起作用。但是，您需要更改所有使用的地点。
而不是将其称为：
free_our_ptr(&arr,nrows,ncols);
您需要将其称为：
free_our_ptr(arr,nrows,ncols);
^^^ No &
答案 1 :(得分：1)
您将指向指针的指针传递给函数free_our_ptr，该指针指向dynminc已分配的内存。要么取消引用函数内的指针：
void free_our_ptr(int ***arr,int nrows,int ncols)
{
int i;
for(i=0;i<nrows;i++)
{
free((*arr)[i]);
// ^
}
free(*arr);
// ^ type of arr is int***
}
或者将指向动态分配内存的指针传递给函数free_our_ptr：
void free_our_ptr( int **arr,int nrows,int ncols )
// ^^
{
int i;
for(i=0;i<nrows;i++)
{
free( arr[i] );
}
free( arr );
}
除此之外，你必须像这样分配你的记忆：
arr = malloc( nrows * sizeof(int*) );
// ^ type of arr is int** and type of an element is int*
for(i=0;i<nrows;i++)
{
arr[i] = malloc( ncols * sizeof(int) );
}
此外，我建议您从功能free_our_ptr(&arr,nrows,ncols);，numbers，square，cube和multiples_of_4中删除multiples_of_5。释放main中的内存，因为您也在main中分配了内存。