Stirng Length Calculation

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I want to calculate string length using this code in visual studio 2008,the code is

C++

void main(){
      char *str;
      int count = 0,i;
      
      printf("\nEnter the String: ");
      gets(str);
      for(i=0;str[i]!='\0';i++){
            count++;
      }
      printf("\nThe length of the string is %d.",count);
      getch();
}

but I am getting error

C++

"Unhandled exception at 0x6a4794af (msvcr90d.dll) : 0xC0000005: Access violation writing location 0x013f575d."

How to solve please help
[Updated]

C#

void main(){
      char *str="";
      int count = 0,i;

      printf(&quot;\nEnter the String: &quot;);
      gets(str);
      for(i=0;str[i]!='\0';i++){
            count++;
      }
      printf(&quot;\nThe length of the string is %d.&quot;,count);
      getch();
}

but it giving same error please help

Posted 20-Mar-13 0:07am

debarunb

Updated 20-Mar-13 2:17am

v3

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nv3 · Answer 1 · 2013-03-20T00:25:00

You are passing to gets an uninitialized pointer. So gets tries to write its output to some weird memory location. That's what the "Access violataion" comes from.

Allocate a buffer for the line that you want to read and pass that buffer to gets, for example:

C++

char lineBuffer[200];
gets (lineBuffer);

Just as a note for the time when you are getting more advanced in C++: There are better ways to read a line than gets. gets has the disadvantage that you can't tell it, how long your buffer is; and if your input is long enough it therefore overwrites the buffer end and corrupts your memory.

CHill60 · Answer 2 · 2013-03-20T00:29:00

Solution 2

It's because of the way you are declaring and using str - there is no memory allocated to it in your code.
See the example here cplusplus.com reference[^] for one way of doing it but you would be better off using fgets see

this post [^] for a suggestion using that

Posted 20-Mar-13 0:29am

CHill60

Matthew Faithfull · Answer 3 · 2013-03-20T00:29:00

Solution 3

It looks like you're passing an uninitialized pointer to gets.

Try replacing the line
char* str;

with
char str[ 81 ]; //room for 80 chars + '\0'

See if this gets you any further.

Posted 20-Mar-13 0:29am

Matthew Faithfull

v2

Comments

debarunb 20-Mar-13 11:01am

but I am declare it as char* str="" but same error happens

Matthew Faithfull 20-Mar-13 12:13pm

That doesn't quite follow my suggestion. char* str="" creates a pointer to an empty string consisting of a single 0 byte. There's no room in that single byte for gets to write the characters you enter so you need to give it the array of character space (multiple bytes) it requires or it overruns into memory it's not allowed to access and that's what causes the crash.

José Amílcar Casimiro · Answer 4 · 2013-03-20T00:29:00

Hi,

char* str; -> this variable is not initialized.

Try this:

C#

char *str = (char*)malloc(256);
int count = 0,i;

printf("\nEnter the String: ");
gets(str);
for(i=0;str[i]!='\0';i++){
      count++;
}
printf("\nThe length of the string is %d.",count);
free(str);
getch();

strlen function will calculate string length for you.

Good luck.

Stirng Length Calculation

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