变长数组

C/C++ code

#include<stdio.h>#define ROWS 3#define COLS 4int sum2d(int rows,int cols,int ar[rows][cols]);int main(void){    int i,j;    int rs=3;    int cs=10;    int junk[ROWS][COLS]={        {2,4,6,8},        {3,5,7,9},        {12,10,8,6}                      //2唯数组    };    int morejunk[ROWS-1][COLS+2]={               {20,30,40,50,60,70},        {5,6,7,8,9,10}    };                                   //另一个二维数组      int varr[rs][cs];    for(i=0;i<rs;i++)        for(j=0;j<cs;j++)            varr[i][j]=i*j+j;            //变长数组，不知道到底什么叫变长数组    printf("3x5 array\n");    printf("Sum of all elements=%d\n",sum2d(ROWS,COLS,junk));  //调用函数计算第一个二维数组的和    printf("2x6 array\n");    printf("Sum of all elements=%d\n",sum2d(ROWS-1,COLS+2,morejunk);//调用函数计算第二个二维数组的和    printf("3x10 VLA\n");    printf("Sum of all elements=%d\n",sum2d(rs,cs,varr)); //调用函数计算变长数组的和    return 0;}int sum2d(int rows,int cols,int ar[rows][cols])//通常函数定义都是sum(int ar[][cols])，这个怎么可以列也可以传递值？{    int r;    int c;    int tot=0;    for(r=0;r<rows;r++)        for(c=0;c<cols;c++)            tot+=ar[r][c];        return tot;}

d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(4) : error C2057: expected constant expression
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(4) : error C2466: cannot allocate an array of constant size 0
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(4) : error C2057: expected constant expression
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(4) : error C2466: cannot allocate an array of constant size 0
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(4) : error C2087: '<Unknown>' : missing subscript
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(19) : error C2057: expected constant expression
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(19) : error C2466: cannot allocate an array of constant size 0
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(19) : error C2057: expected constant expression
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(19) : error C2466: cannot allocate an array of constant size 0
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(19) : error C2087: '<Unknown>' : missing subscript
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(19) : error C2133: 'varr' : unknown size
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(24) : error C2664: 'sum2d' : cannot convert parameter 3 from 'int [3][4]' to 'int [][1]'
Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(26) : error C2664: 'sum2d' : cannot convert parameter 3 from 'int [2][6]' to 'int [][1]'
Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(26) : error C2143: syntax error : missing ')' before ';'
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(31) : error C2057: expected constant expression
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(31) : error C2466: cannot allocate an array of constant size 0
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(31) : error C2057: expected constant expression
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(31) : error C2466: cannot allocate an array of constant size 0
d:\program files\vc6.0\myprojects\10_lizi_18\1.cpp(31) : error C2087: '<Unknown>' : missing subscript


[解决办法]
C99支持变长数组－－但很有限。LZ先试试 一维数组，先看看你的编译器对C99的支持程度，再试试二维的，我的经历是，变长数组只在一级调用层可以用（向下调用时传变长数组相关参数可以），但不能再向下传了。