This is to resolve bug 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
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