C-Language-Basics on KnightLi Blog

C Struct Initialization and Character/String Fields

Fri, 13 Jun 2025 00:00:00 +0000

Positional Initialization at Declaration

struct InitMember {
    int first;
    double second;
    char *third;
    float four;
};

struct InitMember test = { -10, 3.141590, "method one", 0.25f };

Order matters in positional initialization.

Assignment After Declaration

struct InitMember test;

test.first = -10;
test.second = 3.141590;
test.third = "method two";
test.four = 0.25f;

Designated Initializers (Recommended for readability)

struct InitMember test = {
    .first = -10,
    .second = 3.141590,
    .third = "method three",
    .four = 0.25f
};

Notes for String Members

char * points to a string literal or dynamically allocated memory.
If writable storage is required, use char array[N] and copy content.
Be careful with lifetime and mutability of pointed strings.

C++-Style Key-Value Initialization

This style is similar to designated initialization in intent: it makes the member name visible and avoids depending only on positional order.

struct InitMember test = {
    second: 3.141590,
    third: "method three",
    first: -10,
    four: 0.25
};