unions Questions
17
Solved
Is there any good example to give the difference between a struct and a union?
Basically I know that struct uses all the memory of its member and union uses the largest members memory space. Is the...
2
The spec (GCC type attributes amongst others) states that __attribute__((packed)) can be applied to a struct or a union.
Since all union fields' storage overlap, what does the attribute actually do...
Finedrawn asked 10/3, 2022 at 12:46
1
Solved
Suppose I have a struct that contains a union with const members, like so:
struct S
{
// Members
const enum { NUM, STR } type;
union
{
const int a;
const std::string s;
};
// Constructo...
4
Solved
I found one code implemented as the similar demo shown below ..
struct st
{
int a;
struct
{
int b;
};
};
6.58 Unnamed struct/union fields within structs/unions
As permitted by ISO C11.
B...
3
Solved
C++11 gave us to possibility to use non-POD types within unions, say I have the following piece of code;
union
{
T one;
V two;
} uny;
Somewhere within my class, only one member will be active ...
Mutinous asked 4/11, 2013 at 8:42
3
Solved
I have used bit field with a structure like this,
struct
{
unsigned int is_static: 1;
unsigned int is_extern: 1;
unsigned int is_auto: 1;
} flags;
Now i wondered to see if this can be done wi...
Glob asked 4/7, 2012 at 9:41
4
I came across some code (it's in a library from Microchip) which has a union.
All was good, until I saw it assigned values to different members of the union right after each other. My immediate tho...
1
Solved
In the following program the union U has two fields a and b, each with distinct default value. If one creates a variable of type U using aggregate initialization {} what are the value and the activ...
Marlea asked 22/8, 2021 at 12:40
2
Solved
I am currently working on programming a pool allocator. My question boils down to the following code:
template <typename T>
union myUnion {
T data;
myUnion<T>* nextUnion;
};
void som...
Trilley asked 2/5, 2017 at 21:24
5
Solved
I am building a class that has a union for its matrix data, however, I can only get it compile when I do not have a name for the struct\union. However, with a higher level warning level (four on vi...
1
Solved
I want to represent a 32-bit number using RGBA values, is it portable to generate the values for said number using a union? Consider this C code;
union pixel {
uint32_t value;
uint8_t RGBA[4];
};...
4
Solved
I'm writing some library code that exposes a const pointer to users but during certain operations I need to change where this pointer points (behind the scenes switcheroo tricks). One idea I had to...
Vanny asked 3/3, 2021 at 14:30
3
Solved
I am working on optimization of a project. It contains a struct of an options in which user can select a single option at a time. In addition to the option, we also use a flag variable to check whi...
3
Solved
Is there a better way to build a move constructor for a union-like class? If I were to have a union-like class like the class in the following code, is there a way to build the class or the move co...
Weinman asked 12/3, 2015 at 0:57
8
Solved
There's no way to do something like this, in C++ is there?
union {
{
Scalar x, y;
}
Scalar v[2];
};
Where x == v[0] and y == v[1]?
2
Solved
For a project I'm working on, it's desirable to have a generic "pointer to a function" type. However, in C, to have a pointer to a function, you need to specify the prototype in the type ...
Donley asked 19/11, 2020 at 20:41
1
union data {
double number2;
char name[20];
};
int main() {
printf("%i\n", sizeof(union data));
return 0;
}
I expected it to be 20 because it is the largest, but the result ...
3
Solved
Whenever I see examples of union, they are always different types. For example, from MSDN:
// declaring_a_union.cpp
union DATATYPE // Declare union type
{
char ch;
int i;
long l;
float f;
dou...
16
Solved
I have used unions earlier comfortably; today I was alarmed when I read this post and came to know that this code
union ARGB
{
uint32_t colour;
struct componentsTag
{
uint8_t b;
uint8_t g;
...
Monmouthshire asked 22/2, 2010 at 11:17
1
I saw such union inside struct definition in pure c code in Linux kernel sources struct cma_multicast (it's not the only one place. Seems that it is some common practice):
struct cma_multicast {
s...
Regulable asked 3/8, 2020 at 12:30
2
Solved
Does C++ guarantee that offsetof(U, m) always returns zero for any union U and its member m or are there cases when it's non-zero?
union U {
M m;
...
};
1
Solved
On the one hand, I have learned that numbers that can be int or float should be type annotated as float (sources: PEP 484 Type Hints and this stackoverflow question):
def add(a: float, b: float):
...
Scholasticate asked 4/7, 2020 at 5:54
2
Solved
I'm attempting to implement a tagged union.
My understanding was that in a C++ union, the non-trivial (i.e. not empty) destructors of non-static members are never called, thus we have to call them ...
Wheels asked 24/6, 2020 at 12:45
4
I guess this must have been asked before, but I could not get a specific yes/no answer.
I have this code snippet :
union integer_to_byte
{
signed int IntPart;
unsigned char BytePart[2];
};
typ...
Munafo asked 24/3, 2020 at 14:31
12
Solved
I recently came across a great data structures book,"Data Structures Using C" (c) 1991, at a local Library book sale for only $2. As the book's title implies, the book covers data structures using ...
Landgraviate asked 13/5, 2009 at 13:47
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