1 files changed, 58 insertions, 16 deletions
diff --git a/EdkCompatibilityPkg/Foundation/Include/EfiStdArg.h b/EdkCompatibilityPkg/Foundation/Include/EfiStdArg.h
index 9ff66e4..bbec17b 100644
--- a/EdkCompatibilityPkg/Foundation/Include/EfiStdArg.h
+++ b/EdkCompatibilityPkg/Foundation/Include/EfiStdArg.h
@@ -58,7 +58,14 @@ Abstract:
 #ifndef _EFISTDARG_H_
 #define _EFISTDARG_H_
 
-#define _EFI_INT_SIZE_OF(n) ((sizeof (n) + sizeof (UINTN) - 1) &~(sizeof (UINTN) - 1))
+/**
+  Return the size of argument that has been aligned to sizeof (UINTN).
+
+  @param  n    The parameter size to be aligned.
+
+  @return The aligned size.
+**/
+#define _INT_SIZE_OF(n) ((sizeof (n) + sizeof (UINTN) - 1) &~(sizeof (UINTN) - 1))
 
 #if defined(__CC_ARM)
 //
@@ -83,9 +90,7 @@ Abstract:
 
 #define VA_END(Marker)                ((void)0)
 
-#define VA_COPY(Dest, Start)          __va_copy (Dest, Start)
-
-#elif defined(__GNUC__)
+#elif defined(__GNUC__) && !defined(NO_BUILTIN_VA_FUNCS)
 //
 // Use GCC built-in macros for variable argument lists.
 //
@@ -102,23 +107,60 @@ typedef __builtin_va_list VA_LIST;
 
 #define VA_END(Marker)               __builtin_va_end (Marker)
 
-#define VA_COPY(Dest, Start)         __builtin_va_copy (Dest, Start)
-
 #else
+///
+/// Variable used to traverse the list of arguments. This type can vary by 
+/// implementation and could be an array or structure. 
+///
+typedef CHAR8 *VA_LIST;
 
-//
-// Also support coding convention rules for var arg macros
-//
-#ifndef VA_START
+/**
+  Retrieves a pointer to the beginning of a variable argument list, based on 
+  the name of the parameter that immediately precedes the variable argument list. 
 
-typedef CHAR8 *VA_LIST;
-#define VA_START(ap, v) (ap = (VA_LIST) & (v) + _EFI_INT_SIZE_OF (v))
-#define VA_ARG(ap, t)   (*(t *) ((ap += _EFI_INT_SIZE_OF (t)) - _EFI_INT_SIZE_OF (t)))
-#define VA_END(ap)      (ap = (VA_LIST) 0)
-#define VA_COPY(dest, src) ((void)((dest) = (src)))
+  This function initializes Marker to point to the beginning of the variable  
+  argument list that immediately follows Parameter.  The method for computing the 
+  pointer to the next argument in the argument list is CPU-specific following the 
+  EFIAPI ABI.
 
-#endif
+  @param   Marker       The VA_LIST used to traverse the list of arguments.
+  @param   Parameter    The name of the parameter that immediately precedes 
+                        the variable argument list.
+  
+  @return  A pointer to the beginning of a variable argument list.
+
+**/
+#define VA_START(Marker, Parameter) (Marker = (VA_LIST) & (Parameter) + _INT_SIZE_OF (Parameter))
 
+/**
+  Returns an argument of a specified type from a variable argument list and updates 
+  the pointer to the variable argument list to point to the next argument. 
+
+  This function returns an argument of the type specified by TYPE from the beginning 
+  of the variable argument list specified by Marker.  Marker is then updated to point 
+  to the next argument in the variable argument list.  The method for computing the 
+  pointer to the next argument in the argument list is CPU-specific following the EFIAPI ABI.
+
+  @param   Marker   VA_LIST used to traverse the list of arguments.
+  @param   TYPE     The type of argument to retrieve from the beginning 
+                    of the variable argument list.
+  
+  @return  An argument of the type specified by TYPE.
+
+**/
+#define VA_ARG(Marker, TYPE)   (*(TYPE *) ((Marker += _INT_SIZE_OF (TYPE)) - _INT_SIZE_OF (TYPE)))
+
+/**
+  Terminates the use of a variable argument list.
+
+  This function initializes Marker so it can no longer be used with VA_ARG().  
+  After this macro is used, the only way to access the variable argument list is 
+  by using VA_START() again.
+
+  @param   Marker   VA_LIST used to traverse the list of arguments.
+  
+**/
+#define VA_END(Marker)      (Marker = (VA_LIST) 0)
 
 #endif