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: warning C4172: returning address of local variable or temporary

Posted on 2004-09-13
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Last Modified: 2007-12-19
I get this warning on the following  piece of code.  Can anyone tell me how to stop it please?
//converts the string data type to char array
char* stringToChar(string temp)                              
{                                          
      char arr[BIRD_SIZE];                              
      int i=0;                                          while(temp[i]!='\0')  
      {
      arr[i]=temp[i];                                    i++;                                          }                                          arr[i]='\0';                                          return(arr);                              
}                                                                                    
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Question by:KazIT
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3 Comments
 

Author Comment

by:KazIT
ID: 12049871
//converts the string data type to char array
char* stringToChar(string temp)                                          
{                                                                                    
      char arr[BIRD_SIZE];                                                
      int i=0;                                                                  
      while(temp[i]!='\0')  
      {
            arr[i]=temp[i];                                                      
            i++;                                                                  
      }                                                                              
      arr[i]='\0';                                                                  
      return(arr);                                                                  
}                                                                                    
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Accepted Solution

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Indrawati earned 250 total points
ID: 12050101
An easier way: if you are using C++ std::str, you can use it c_str member function to get its char representation. It's constant, however, you you may have to use strcpy to copy it to the resulting buffer.

Back to the question: the cause of the warning message is because you're returning arr, which is a local variable and it's not valid anymore after the function exits. You can change it to:

void stringToChar(string temp, char *arr)                                  
{                                                                                      
     int i=0;                                                      
     while(temp[i]!='\0')  
     {
          arr[i]=temp[i];                                            
          i++;                                                      
     }                                                                
     arr[i]='\0';                                                            
}

to remove the warning message.
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Author Comment

by:KazIT
ID: 12050109
thank you Indrawati

Kaz
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