My questions are:Code:union{ struct st{ char c; char d; short s; }token; int i; }u; int main(){ u.i=0xff00dd01; char c = u.token.c; cout<<sizeof(u)<<endl; }
1. why sizeof(u) is 4? I think it shall be 8 right?
2. What is c's value after execution?
thanks
Why should it be? An int is 4, and char is 1 (*2), short is 2, so the struct also adds up to 4.1. why sizeof(u) is 4? I think it shall be 8 right?
0x1, assuming your machine is little-endian (therefore the least significant byte of i is stored first, overlapping with c)2. What is c's value after execution?
2) c's value is green. Or marmelade. It depends on your system.
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CornedBee
"There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
- Flon's Law
A union makes all members share the same memory, only with different representations. I've used this for binary readers as an example (to read structured data):
(forgive errors, I'm a C# user nowadays)Code:class CPointer { public: union { void* Void; char* Char; short* Short; int* Int; float* Float; } }; CPointer Pointer; Pointer.Char = PointToDataSomwhere(); int IntVal1 = *Pointer.Int++; int IntVal2 = *Pointer.Int++; float FloatVal1 = *Pointer.Float++; int IntVal3 = *Pointer.Int++; float FloatVal2 = *Pointer.Float++; float FloatVal3 = *Pointer.Float++; short ShortVal1 = *Pointer.Short++; int IntVal4 = *Pointer.Int++;
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