Mastodawn

I'm writing C++. I have a struct

struct ExampleStruct {
int32_t i;
bool a;
bool b;
}

I know I'm running on a modern CPU such as x86_64 or ARM64, and I know I'm using a modern compiler such as recent clang, recent gcc, or recent msvc.

The byte offsets of "a" and "b", relative to the start of ExampleStruct, are:

4 and 5

30.2%

4 and 8

16.3%

It depends on platform/compiler

44.1%

U gotta use a #pragma

9.4%

Poll ended at Jan 16 at 8:29pm.

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Josh Simmons Jan 15

@mcc int is 4 bytes size, 4 bytes alignment, bools are 1 byte size, 1 byte alignment. the whole struct is 8 bytes size 4 bytes alignment. there's two bytes of padding at the end. mostly this is load bearing abi stuff so it shouldn't really change underneath you, even if it's not strictly specified by the C++ standard (it is specified by the platform ABI).

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Josh Simmons

@mcc e.g. i believe sizeof(bool) can still be something stupid by the C++ law, in which case you might have a fun time. but if you find a platform where `sizeof(bool)` isn't 1 you can throw it into the fire anyway.