What 's the use of memset() return value?

memset() is a C standard library function used to initialize memory content. It is commonly used to initialize a block of memory to a specific value. The function prototype is defined in the string.h header file, with the following format:

c
void *memset(void *s, int c, size_t n);

• s is a pointer to the memory block to be filled.
• c is the value to set, although the parameter type is int, the function converts this value to unsigned char before copying it to the memory.
• n is the number of bytes to set.

Purpose of the Return Value

The return value of memset() is a pointer to the first byte, which is identical to the parameter s. This return value is frequently utilized in chained function calls, where multiple functions are invoked sequentially within a single line of code to enhance conciseness and readability.

Example:

Suppose you are developing a program that requires initializing a structure and copying it to a new location. You can leverage memset() to initialize the structure and immediately pass its return value to other functions, such as memcpy().

c
#include <string.h>
#include <stdio.h>

typedef struct {
    int age;
    float salary;
} Employee;

int main() {
    Employee emp;
    
    // Initialize and immediately use the return value of memset()
    Employee *pEmp = memcpy(malloc(sizeof(Employee)), memset(&emp, 0, sizeof(Employee)), sizeof(Employee));
    
    if (pEmp != NULL) {
        pEmp->age = 30;
        pEmp->salary = 50000.0;
        
        printf("Age: %d, Salary: %.2f\n", pEmp->age, pEmp->salary);
    }

    // Free dynamically allocated memory
    free(pEmp);
    
    return 0;
}

In this example, memset() initializes all fields of the emp structure to 0, and its return value &emp (the memory address) is directly used as the source address for memcpy(), achieving optimized code and conciseness. This approach is particularly valuable for resource initialization and configuration tasks, especially when ensuring data structures are safely zeroed.