Can a union be initialized in the declaration?

c initialization declaration unions
semaj picture semaj · Jan 27, 2010 · Viewed 16.1k times · Source

For example, say we have a union

typedef union {
unsigned long U32;
float f;
}U_U32_F;

When a variable of this union type is declared, is there a way to set an initial value?

U_U32_F u = 0xffffffff;   // Does not work...is there a correct syntax for this?

Answer

Christoph picture Christoph · Jan 27, 2010

Use an initializer list:

U_U32_F u = { 0xffffffff };

You can set other members than the first one via

U_U32_F u = { .f = 42.0 };

Related questions

What happens to a declared, uninitialized variable in C? Does it have a value?

If in C I write: int num; Before I assign anything to num, is the value of num indeterminate?

Read More
Assign multiple values to array in C

Is there any way to do this in a condensed form? GLfloat coordinates[8]; ... coordinates[0] = 1.0f; coordinates[1] = 0.0f; coordinates[2] = 1.0f; coordinates[3] = 1.0f; coordinates[4] = 0.0f; coordinates[5] = 1.0f; coordinates[6] = 0.0f; coordinates[7] = 0.0f; return coordinates; Something like coordinates = {1.0f, ...};?

Read More
How to initialize all members of an array to the same value?

I have a large array in C (not C++ if that makes a difference). I want to initialize all members of the same value. I could swear I once knew a simple way to do this. I could use memset() …

Read More