sizeof

Returns the number of bytes of the given expression or type. The result size_t, is of an unsigned integer type.

size_t sizeof expression

or

size_t sizeof (type) 

Example

The following example uses the memset function to fill a structure, about_app, with zeros before initializing it. The return value of sizeof is used as a parameter to memset, to precisely calculate the size of the structure to be filled.

    struct about_app {
        char * version;
        int field1;
        int field2;
    };

// Global scope 

    struct about_app a; 
    a.field1 = 12;
    a.field2 = 13;

// Set all fields to zero 
    memset(&a, 0, sizeof(struct about_app)); 

// Display the field values (0)

    lr_output_message ("After memset field1=%d field2=%d", a.field1, a.field2);
    a.version = "app version 1.0";
    a.field1 = 5;
    a.field2 = 6;
    lr_output_message ("Now, field1=%d field2=%d", a.field1, a.field2);

Example: Output:
Action.c(18): After memset field1=0 field2=0
Action.c(23): Now, field1=5 field2=6