Re: [edk2-devel] [Question] using Flexible Array Member in Structure.

["Pedro Falcato" <pedro.falcato@gmail.com>]

On Wed, Apr 3, 2024 at 10:27 AM levi.yun <yeoreum.yun@arm.com> wrote:
>
> Hello all!
>
> while I see the code. I have one question related using Flexible Array
> Member.
>
> For example)
>
> ///
> /// Socket Type Data.
> ///
> typedef struct {
>    EFI_ACPI_6_4_PMTT_COMMON_MEMORY_DEVICE CommonMemoryDeviceHeader;
>    UINT16 SocketIdentifier;
>    UINT16 Reserved;
>    // EFI_ACPI_6_4_PMTT_COMMON_MEMORY_DEVICE MemoryDeviceStructure[];
> } EFI_ACPI_6_4_PMTT_SOCKET_TYPE_DATA;
>
>
> ///
> /// Socket Type Data.
> ///
> typedef struct {
>    EFI_ACPI_6_4_PMTT_COMMON_MEMORY_DEVICE CommonMemoryDeviceHeader;
>    UINT16 SocketIdentifier;
>    UINT16 Reserved;
>    EFI_ACPI_6_4_PMTT_COMMON_MEMORY_DEVICE  MemoryDeviceStructure[]
> }

This change might be okay. Both variants may be size (and
layout)-equivalent. See https://godbolt.org/z/364e4T4a7. You need to
check if e.g there's any padding after Reserved and before
MemoryDeviceStructure.
Basically make sure member offsets and sizes remain stable.

Thanks,
Pedro


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