Nicolas,
#pragma pack() aligns to the C ABI convention. #pragma pack(1) byte packs the
structure.
The EFI C ABI is carefully defined in the UEFI specification to be the same for
all processor architectures. Per UEFI spec:
2.3.1 Data Types
Table 6 lists the common data types that are used in the interface definitions,
and Table 7 lists their modifiers. Unless otherwise specified all data types
are naturally aligned. Structures are aligned on boundaries equal to the
largest internal datum of the structure and internal data are implicitly padded
to achieve natural alignment.
So #pragma pack(1) is only required if you need to byte pack your structure.
So:
#pragma pack (1)
struct {
UINT32 One;
UINT64 Two;
} EXAMPLE_12_BYTE_STRUCT;
#pragma pack()
struct {
UINT32 One;
UINT64 Two;
} EXAMPLE_16_BYTE_STRUCT;
Andrew Fish
On Aug 23, 2012, at 7:21 PM, nicolas wrote:
> hi, experts:
> I found using "#pragma pack()" pre-compile syntax for some data structs, but
> not for some other data struct in MdePkg\Include\Protocol\Dhcp6.h .
> So, is there some considerations for using this pre-compile syntx?
>
> If i used "#pragma pack()" pre-compile syntax for all my own defined data
> structs, having any side effects?or not.
>
> best wishes,
>
>
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