{Patch/documentation} PR 35054 Document #pragma push|pop_macro

[Danny Smith]

This provides missung user documentation for the new extension
#pragma_push_macro and #pragma_pop_macro.

OK for 4.3.0?

:ADDPATCH documentation:

2008-02-05  Danny Smith  <dannysmith@users.sourceforge.net>

	PR 35054
	* doc/extend.texi (Push/Pop Macro Pragmas): Add documentation
	for #pragma_push_macro and #pragma_pop_macro

Index: extend.texi
===================================================================
--- extend.texi	(revision 131857)
+++ extend.texi	(working copy)
@@ -10831,6 +10831,7 @@
 * Weak Pragmas::
 * Diagnostic Pragmas::
 * Visibility Pragmas::
+* Push/Pop Macro Pragmas::
 @end menu

 @node ARM Pragmas
@@ -11146,6 +11147,34 @@

 @end table

+
+@node Push/Pop Macro Pragmas
+@subsection Push/Pop Macro Pragmas
+For compatibility with MSVC, GCC supports the Win32 style pragmas
+@samp{#pragma push_macro(@var{"macro_name"})} and @samp{#pragma
+pop_macro(@var{"macro_name"})}.
+
+@enumerate
+@item @code{#pragma push_macro(@var{"macro_name"})} saves the
+value of the macro named as @var{macro_name} to the top of the stack for
+this macro
+@item @code{#pragma pop_macro(@var{"macro_name"})} sets the
+value of the macro named as @var{macro_name} to the value on top of
+the stack for this macro. If the stack for @var{macro_name} is empty,
+the value of the macro remains unchanged.
+@end enumerate
+
+For example:
+
+@smallexample
+#define X  1
+#pragma push_macro("X")
+#undef X
+#define X -1
+#pragma pop_macro("X")
+int x [X];
+@end smallexample
+
 @node Unnamed Fields
 @section Unnamed struct/union fields within structs/unions
 @cindex struct