Question

The offsetof macro seems not to work under C++/CLI.

This works fine in unmanaged C++, but throws ‘error C2275: ‘Entity’ :illegal use of this type as an expression’ error in CLI.

struct Property{      char* label;      PropertyTypes type;      unsigned int member_offset;      unsigned int position;      unsigned char bit_offset; };  struct Entity{      ...      bool transparent;      ... };  Property property = {'Transparent',             TYPE_BOOL,               offsetof(Entity, transparent),         0,         0}; // C2275 HERE 

Does CLI have some replacement?

Answer 1

My guess would be that the compiler message boils down to: ‘offsetof’ is not a known macro and if it was a function its parameters must not contain a typename.

Edit: As somebody pointed out in the comments, offsetof is actually part of the std lib. So what’s missing is probably just

#include <cstddef> 

Alternatively, you can use this macro implementation (taken from Win32/MFC headers):

#ifdef _WIN64     #define OFFSET_OF( s, m )\       (size_t)((ptrdiff_t)&reinterpret_cast<const volatile char&>((((s*)0)->m)) ) #else     #define OFFSET_OF( s, m )\       (size_t)&reinterpret_cast<const volatile char&>((((s*)0)->m)) #endif