calloc
allocates the requested memory and returns a pointer to it. It also sets allocated memory to zero.
In case you are planning to use your string
as empty string all the time:
char *string = NULL;
string = (char*)calloc(1, sizeof(char));
In case you are planning to store some value in your string
later:
char *string = NULL;
int numberOfChars = 50; // you can use as many as you need
string = (char*)calloc(numberOfChars + 1, sizeof(char));
It's a bit late but I think your issue may be that you've created a zero-length array, rather than an array of length 1.
A string is a series of characters followed by a string terminator ('\0'
). An empty string (""
) consists of no characters followed by a single string terminator character - i.e. one character in total.
So I would try the following:
string[1] = ""
Note that this behaviour is not the emulated by strlen
, which does not count the terminator as part of the string length.
string[0] = "";
"warning: assignment makes integer from pointer without a cast
Ok, let's dive into the expression ...
0
an int: represents the number of chars (assuming string
is (or decayed into) a char*) to advance from the beginning of the object string
string[0]
: the char
object located at the beginning of the object string
""
: string literal: an object of type char[1]
=
: assignment operator: tries to assign a value of type char[1]
to an object of type char
. char[1]
(decayed to char*
) and char
are not assignment compatible, but the compiler trusts you (the programmer) and goes ahead with the assignment anyway by casting the type char*
(what char[1]
decayed to) to an int
--- and you get the warning as a bonus. You have a really nice compiler :-)
To achieve this you can use:
strcpy(string, "");
Assigning string literals to char array is allowed only during declaration:
char string[] = "";
This declares string as a char array of size 1 and initializes it with \0
.
Try this too:
char str1[] = "";
char str2[5] = "";
printf("%d, %d\n", sizeof(str1), sizeof(str2)); //prints 1, 5
In addition to Will Dean's version, the following are common for whole buffer initialization:
char s[10] = {'\0'};
or
char s[10];
memset(s, '\0', sizeof(s));
or
char s[10];
strncpy(s, "", sizeof(s));
You want to set the first character of the string to zero, like this:
char myString[10];
myString[0] = '\0';
(Or myString[0] = 0;
)
Or, actually, on initialisation, you can do:
char myString[10] = "";
But that's not a general way to set a string to zero length once it's been defined.
I think Amarghosh answered correctly. If you want to Initialize an empty string(without knowing the size) the best way is:
//this will create an empty string without no memory allocation.
char str[]="";// it is look like {0}
But if you want initialize a string with a fixed memory allocation you can do:
// this is better if you know your string size.
char str[5]=""; // it is look like {0, 0, 0, 0, 0}
Source: Stackoverflow.com