未处理的异常错误执行数学操作

C++ GET Method Unhandled exception error performing mathematical operation

本文关键字：操作 执行数 错误 异常 未处理      更新时间：2023-10-16

有人能帮帮我吗?我得到一个未处理的异常错误"在program.exe中的0x1027d440 (msvcr100d.dll)未处理的异常:0xC0000005:访问违规读取位置0x00000000。"现在程序实际上并没有执行任何操作。所有的答案都会返回，就好像用户选择了第一个单选按钮一样(我设置了5个单选按钮来选择要使用的方法)。但答案总是为零?我需要改变什么才能得到它所以如果用户选择说。然后是减法?我有它设置的值，但我猜有一个错误的地方。谢谢!

这是我在HTML页面

上的设置
<!DOCTYPE HTML PUBLIC "-//SoftQuad Software//DTD HoTMetaL PRO 6.0::19990601::extensions to HTML 4.0//EN" "hmpro6.dtd">
<HTML> 
  <HEAD> 
     <TITLE>Calculations</TITLE> 
  </HEAD> 
  <BODY> 
<P>
<p align="center">
<td>Select which Mathmatical operation you would like to perform:</td>
<BR> </P> 
<table border="0" align="center">
<tr>
<td>Enter a number to be calculated:</td>
<td><INPUT TYPE="TEXT" NAME="Number1" SIZE="14" MAXLENGTH="20"></p></td>
</tr>
<tr>
<td>Enter a second number to be calculated:</td>
<td><INPUT TYPE="TEXT" NAME="Number2" SIZE="14" MAXLENGTH="20"></p></td>
</tr>
<tr>
     <FORM ACTION="http://localhost:8080/cgi-bin/calc.exe" METHOD=”GET">
<p align="center">
 <INPUT TYPE = "RADIO" NAME = "mathOperation" VALUE = "0" ><b>Addition</B>
<BR>
 <INPUT TYPE = "RADIO" NAME = "mathOperation" VALUE = "1" ><b> Subtraction</B>
<BR>
  <INPUT TYPE = "RADIO" NAME = "mathOperation" VALUE = "2" ><b> Multiplication</B>
<BR>
  <INPUT TYPE = "RADIO" NAME = "mathOperation" VALUE = "3" ><b> Division</B>
<BR>
  <INPUT TYPE = "RADIO" NAME = "mathOperation" VALUE = "4" ><b> Square Root</B>
<BR>
</TR>
</table>
<p align="center">Enter the number of decimal places you'd like displayed: 
                <input TYPE="text" NAME="Decimal" size="14" MAXLENGTH="50">
        <P ALIGN="CENTER"><INPUT TYPE="SUBMIT" NAME="Submit1" CHECKED="CHECKED"
          VALUE="Submit Information"> </P> 
        <P ALIGN="CENTER"><INPUT TYPE="RESET" NAME="Reset1"
          VALUE="Reset Form"></P></FORM> </BODY>
</HTML>
下面是我的代码: 
#include <iostream>
using namespace std;
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
//Function prototype
int getvar(char *, char *, char *);
int main(int argc, char **argv)
{
     int length;        // only up to 32767 chars
     char buffer[1024]; // Buffer size
     char *data;        // Input to program pointer
     char dest1[10];    // Destination fields
     char dest2[10];
     char dest3[10];
     float number1;     // first number 
     float number2;     // second number
     int mathOperation; // operation to perform
     float answer;      // place to store the result

     // GET Method
     if (strcmp(getenv("REQUEST_METHOD"), "GET") == 0)
     {
          // CGI input is located in the QUERY_STRING environment variable
          strcpy( buffer, getenv("QUERY_STRING"));
     }
     else
     {
          // CGI input data is read from standard input
          length=atoi(getenv("CONTENT_LENGTH"));
          data= (char *) malloc(sizeof(char)*(length+1));
          cin.get(data, length);
          strcpy(buffer, data);
          free (data);
     }
     //   Find the program inputs in the user supplied data 
     getvar("Number1",       dest1,buffer);
     getvar("Number2",       dest2,buffer);
     getvar("MathOperation", dest3,buffer);

     //   Convert the data to the right data type
     number1 = (float) atof(dest1);    // The variable number1 contains the first number
     number2 = (float) atof(dest2);    // The variable number2 contains the second number
     mathOperation = atoi(dest3); // The math operation code
     //   Perform the correct mathematical operation based on the
     //   user specifications
     if(mathOperation == 0) // perform addition
     {
          answer = number1 + number2;
          cout << "<p/>n" "Your addition answer is = " <<(answer)<< "<br/>n";
     }
     else if (mathOperation == 1) // perform subtraction
     {
          answer = number1 - number2;
          cout << "<p/>n" "Your subtraction answer is = " <<(answer)<< "<br/>n";
     }
       else if (mathOperation == 2) // perform multiplication
     {
          answer = number1 * number2;
          cout << "<p/>n" "Your answer is = " <<(answer)<< "<br/>n";
     }
       else if (mathOperation == 3) // perform division
     {
          answer = number1 / number2;
          cout << "<p/>n" "Your answer is = " <<(answer)<< "<br/>n";
     }
         else if (mathOperation == 4) // perform square root
     {
          cout << "The square root of " << number1 << " is " << sqrt(number1) << endl;
          cout << "The square root of " << number2 << " is " << sqrt(number2) << endl;
     }
     else
     {
     // I still need to add additional code.. but.. for now..
     }
     cout << "Content-type: text/htmlnn";
     cout << "<html><body>n";

     cout << "</body></html>n";
     return 1;
} 
//(Include the c++ getvar comment block and code here)
    int getvar(char *var, char *dest, char *stream)
    {  
        char *vptr;
        int size, i=0, j=0, hex; /* ptr+i to src, ptr+j to dest */ 
        vptr=strstr(stream, var);  
        if(vptr) ; 
        else return(1); /* 1 for a checkbox thats off */
        if((vptr==stream)||(*(vptr-1)=='&')) ; 
        else return(-1); /* -1 for a var that appears in error */
        size=(int) strlen(var)+1; /* +1 accounts for the = */
        while(*(vptr+size+i)!='&') 
        {      
                if(*(vptr+size+i)=='+') /* output a space */           
                    *(dest+j)=' ';     
                else if(*(vptr+size+i)=='%') /* hex character */           
                        {              
                            sscanf(vptr+size+i+1,"%2x",&hex);              
                            *(dest+j)=(char)hex;               
                            i+=2;          
                        }      
            else *(dest+j)=*(vptr+size+i);     
                i++; j++;  
            }  
        *(dest+j)='';
            return(0);
    }

我认为事情很清楚:

getenv("REQUEST_METHOD")返回一个空指针，strcmp尝试读取它。您应该以编程方式检查环境变量是否存在。

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