Re: [PATCH] MdePkg: correct and clarify documentation of VA_LIST in Base.h

["Gao, Liming" <liming.gao@intel.com>]

Hi, 
  I see you and Laszlo are still in discussion on GCC behavior. Because there is one bug in GCC compiler, the following functions in edk2 must be EFIAPI. Right?

- functions that have a variable argument list and call VA_START / VA_END
- functions that call VA_COPY

Thanks
Liming
> -----Original Message-----
> From: Zenith432 [mailto:zenith432@users.sourceforge.net]
> Sent: Sunday, December 10, 2017 11:43 PM
> To: Gao, Liming <liming.gao@intel.com>; edk2-devel@lists.01.org
> Cc: Kinney, Michael D <michael.d.kinney@intel.com>
> Subject: Re: [PATCH] MdePkg: correct and clarify documentation of VA_LIST in Base.h
> 
> On 10/12/2017 03:53 PM, Gao, Liming wrote:
> > Could you add bug 457 link in the commit message?
> ---
> Subject: [PATCH] MdePkg: correct and clarify documentation of VA_LIST in Base.h
> 
> This is to resolve bug 457.
> https://bugzilla.tianocore.org/show_bug.cgi?id=457
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Zenith432 <zenith432 at users.sourceforge.net>
> ---
>    MdePkg/Include/Base.h | 24 ++++++++++++++++++++----
>    1 file changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/MdePkg/Include/Base.h b/MdePkg/Include/Base.h
> index 02140a5a..19f36872 100644
> --- a/MdePkg/Include/Base.h
> +++ b/MdePkg/Include/Base.h
> @@ -560,13 +560,14 @@ struct _LIST_ENTRY {
>    //  VA_LIST  - typedef for argument list.
>    //  VA_START (VA_LIST Marker, argument before the ...) - Init Marker for use.
>    //  VA_END (VA_LIST Marker) - Clear Marker
> -//  VA_ARG (VA_LIST Marker, var arg size) - Use Marker to get an argument from
> -//    the ... list. You must know the size and pass it in this macro.
> +//  VA_ARG (VA_LIST Marker, var arg type) - Use Marker to get an argument from
> +//    the ... list. You must know the type and pass it in this macro.
>    //  VA_COPY (VA_LIST Dest, VA_LIST Start) - Initialize Dest as a copy of Start.
>    //
> -//  example:
> +//  Example:
>    //
>    //  UINTN
> +//  EFIAPI
>    //  ExampleVarArg (
>    //    IN UINTN  NumberOfArgs,
>    //    ...
> @@ -582,7 +583,7 @@ struct _LIST_ENTRY {
>    //    VA_START (Marker, NumberOfArgs);
>    //    for (Index = 0, Result = 0; Index < NumberOfArgs; Index++) {
>    //      //
> -//      // The ... list is a series of UINTN values, so average them up.
> +//      // The ... list is a series of UINTN values, so sum them up.
>    //      //
>    //      Result += VA_ARG (Marker, UINTN);
>    //    }
> @@ -591,6 +592,21 @@ struct _LIST_ENTRY {
>    //    return Result
>    //  }
>    //
> +//  Notes:
> +//
> +//  This set of macros is intended to support variadic functions that
> +//  use the EFIAPI calling convention.  Variadic functions that use a
> +//  native calling convention should use stdarg.h.
> +//  In particular:
> +//  -- VA_START may only be used in a variadic EFIAPI function.
> +//  -- va_start may only be used in a variadic native function.
> +//  -- VA_START, VA_END, VA_ARG and VA_COPY may only be used on a VA_LIST.
> +//  -- va_start, va_end, va_arg and va_copy may only be used on a va_list.
> +//  -- Both VA_LIST or va_list may be passed as arguments to functions
> +//     of either EFIAPI or native calling conventions.
> +//  -- VA_END, VA_ARG, VA_COPY, va_end, va_arg, and va_copy may be used
> +//     in functions of either calling conventions.
> +//
> 
>    /**
>      Return the size of argument that has been aligned to sizeof (UINTN).
> --
> 2.14.3