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 _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
