Thread: char *a="123"; a[1]='A';//In VC++ has error, TCPP doesn't have

strange problem,

Code:

int main(void){
  char *a = "123456";

  a[2] = 'a' ;

  printf( "%s", a );

  return 0;
}

When compiled in VC++, there is no compile time error but a memory error at run-time.

In TCPP 3.0, there is no problem at all.

what is the problem ? THANKS~

Hello,

The variable a is a string literal. That variable is initialized as a string literal and may subsequently be modified to point elsewhere, but the result is undefined if you try to modify the string contents.

Either define a as an array, or allocate a block of memory to it.


- Stack Overflow

To expand on that, since string literals are not meant to be modified, the compiler is free to put string literals in read-only memory, in which case naturally you won't be able to modify them without causing runtime errors.

As Stack Overflow has mentioned, the simplest fix is to do:
char a[] = "123456";
instead of
char* a = "123456";

The reason it works in one compiler and not the other, is simply because the behaviour is undefined: It may or may not work, depending on what the compiler decides to do; and since there are no rules on what the compiler is supposed to do in this situation, it may do anything.