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Difference between char *str and char str[]

I assign the same string value to a pointer and a char array

char *str = "hello" "world";  
char str1[] = "hello" "world";

Then use sizeof()function to return their lengths

sizeof(str);     //  on my computer, it's 8 !!
sizeof(str1);    //  return 11, which is right

But both of them can be printed out right by %s:

printf("%s\n%s\n", str, str1);

So why does sizeof(str);return a wrong value ?

Solution

  • So why does sizeof(str);return a wrong value ?

    It does not because sizeof returns the size in bytes of the type of its operand. From section 6.5.3.4 The sizeof operator of the C99 standard (draft n869), clause 2:

    The sizeof operator yields the size (in bytes) of its operand, which may be an expression or the parenthesized name of a type. The size is determined from the type of the operand. The result is an integer. If the type of the operand is a variable length array type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an integer constant.

    Therefore:

    sizeof(str)  == sizeof(char*)
sizeof(str1) == sizeof(char[11])