帮助我解决C中的内存访问冲突错误 [英] Help me for an memory access violation error in C

问题描述

我得到内存访问冲突错误，请快速帮帮我!!!!



我写了这样的代码，请注意我的评论错误行

I get memory access violation error, please help me quickly!!!!

I wrote a code like this, kindly note my commented line of error

float  fValue=0;

stpData ->dbpMG1G1_data = ( float  ** ) malloc (sizeof ( float * ) * nRows * nColumns);

while ( NULL != fgets( cpReadString, 6144, fStream ) && nRow < nRows )

{

while ( NULL != cpSubString && nColumn < nColumns )

{
  fValue =  atof(cpSubString) ; 

  stpData ->dbpMG1G1_data[nRow][nColumn] = fValue ; // here I am getting error	
			
  ++nColumn ;
  
}

++nRow ; 
 
}

我在外面写了内存分配代码行循环以便

优化执行速度。是索引问题还是别的？







完成调试错误通知：

I delibratly wrote the memory allocation code line outside the loops so as to
optimze the execution speed. Is it indexing problem or something else?



Complete debugg error notification:

Unhandled exception at 0x0042b9e2 in On_The_Fly-A350.exe: 0xC0000005: Access violation writing location 0xcdcdcdcd.

提前致谢!!!!!!!

Thanks in advance!!!!!!!

推荐答案

你需要一个浮点矩阵（你不需要（nRows * nColumns）的float 指针）。

我认为一个简单的方法是（使用数据而不是 stpData - > dbpMG1G1_data 来简化符号）：

You need a matrix of floats (you don''t need (nRows * nColumns) of float pointers).
I think an easy approach would be (using data instead of stpData ->dbpMG1G1_data to simplify notation):

data = (float *) malloc( sizeof(float) * nRows * nColumns); // linear array of floats
//..
{
  fValue = atof(cpSubString) ; 
  int i = nRow * Columns + nColumn; // bidimensional to linear: [Row][Column] => [i]
  data[i] = fValue;
}

您正在分配一个带有 nRows的一维数组 * nColumns 指向 float 的指针元素并将其转换为 float ** 。这不起作用（在这种情况下，总数组大小将匹配浮点数，因为32位构建的sizeof（float）== sizeof（float *），但访问2-dim成员将导致访问冲突）。



要解决此问题，您有两种选择：



1.使用一维数组并计算索引访问元素时：

You are allocating an 1-dimensional array with nRows * nColumns elements of pointers to float and casting this to a float**. This will not work (the total array size would match for floats in this case because sizeof(float) == sizeof(float *) for 32-bit builds, but accessing 2-dim members will cause access violations).

To fix the problem, you have two options:

1. Use a 1-dimensional array and calculate the index when accessing elements:

stpData->dbpMG1G1_data = (float *)malloc(sizeof(float) * nRows * nColumns);
// ...
stpData ->dbpMG1G1_data[nRow * nColumns + nColumn] = fValue;

1.使用必须使用循环分配的二维数组：

1. Use a 2-dimensional array which must be allocated using a loop:

stpData->dbpMG1G1_data = (float **)malloc(sizeof(float *) * nRows);
int i;
for (i = 0; i < nRows; i++)
    stpData ->dbpMG1G1_data[i] = (float *)malloc(sizeof(float) * nColumns);

第一个版本的格式更多，不需要释放另一个循环中的内存。

The first version is more performat and does not require freeing the memory inside another loop.

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