Conditionally using packed struct with armcc (PACKSTRUCT in BGLib) - c

Question

I try to make work the BLE121LR module with an external MCU (EFM32).
As I can understand, this piece of code declares converting of the struct to binary data, am I right?
Can somebody explain me how to add the ARM (EFM32) support for it?
Thanks a lot!!
Code:
/* Compability */
#ifndef PACKSTRUCT
#ifdef PACKED
#define PACKSTRUCT(a) a PACKED
#else
/*Default packed configuration*/
#ifdef __GNUC__
#ifdef _WIN32
#define PACKSTRUCT( decl ) decl __attribute__((__packed__,gcc_struct))
#else
#define PACKSTRUCT( decl ) decl __attribute__((__packed__))
#endif
#define ALIGNED __attribute__((aligned(0x4)))
#else //msvc
#define PACKSTRUCT( decl ) __pragma( pack(push, 1) ) decl __pragma( pack(pop) )
#define ALIGNED
#endif
#endif
#endif

Answer 1

Yes, packed structs affect how the struct is stored in memory, which is often used as a quick-and-dirty way of converting structs to binary data.
The PACKSTRUCT macro isn't written for the keil armcc compiler. To fix this, we must first find how we can identify when armcc is used. On this page, we can see that armcc provides the define __ARMCC_VERSION, which we can use.
Now, how do we declare a packed struct using armcc? Here, we see that we should use the __packed qualifier:
/* Compability */
#ifndef PACKSTRUCT
#ifdef PACKED
#define PACKSTRUCT(a) a PACKED
#else
/*Default packed configuration*/
#ifdef __GNUC__
#ifdef _WIN32
#define PACKSTRUCT( decl ) decl __attribute__((__packed__,gcc_struct))
#else
#define PACKSTRUCT( decl ) decl __attribute__((__packed__))
#endif
#define ALIGNED __attribute__((aligned(0x4)))
#else // not __GNUC__
#ifdef __ARMCC_VERSION
#define PACKSTRUCT( decl ) __packed decl
#define ALIGNED
#else // Assume msvc
#define PACKSTRUCT( decl ) __pragma( pack(push, 1) ) decl __pragma( pack(pop) )
#define ALIGNED
#endif
#endif
#endif
#endif