cppopts.texi: Update.

* doc/cppopts.texi: Update.
testsuite:
	* gcc.dg/cpp/trad/Wunused.c, gcc.dg/cpp/Wunused.c: Add test
	for documented behaviour.

From-SVN: r55779

gcc/ChangeLog

@@ -1,3 +1,7 @@
+2002-07-26  Neil Booth  <neil@daikokuya.co.uk>
+
+	* doc/cppopts.texi: Update.
+
 2002-07-26  Neil Booth  <neil@daikokuya.co.uk>
 
 	* cppmacro.c (_cpp_create_definition): Don't attempt redefinition

gcc/doc/cppopts.texi

@@ -120,6 +120,17 @@ time it is redefined or undefined.
 Built-in macros, macros defined on the command line, and macros
 defined in include files are not warned about.
 
+@strong{Note:} If a macro is actually used, but only used in skipped
+conditional blocks, then CPP will report it as unused.  To avoid the
+warning in such a case, you might improve the scope of the macro's
+definition by, for example, moving it into the first skipped block.
+Alternatively, you could provide a dummy use with something like:
+
+@smallexample
+#if defined the_macro_causing_the_warning
+#endif
+@end smallexample
+
 @item -Wendif-labels
 @opindex Wendif-labels
 Warn whenever an @samp{#else} or an @samp{#endif} are followed by text.

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2002-07-26  Neil Booth  <neil@daikokuya.co.uk>
+
+	* gcc.dg/cpp/trad/Wunused.c, gcc.dg/cpp/Wunused.c: Add test
+	for documented behaviour.
+
 2002-07-25  Roger Sayle  <roger@eyesopen.com>
 
 	* gcc.c-torture/execute/20020720-1.x: Skip this test on

gcc/testsuite/gcc.dg/cpp/Wunused.c

@@ -26,7 +26,12 @@
 #endif
 used4
 
-unused7
+unused7				/* This does not count as a use.  */
+
+#if 0
+unused5				/* This does not count as a use.  */
+#endif
 #undef unused5
+
 #define unused6
 unused6

gcc/testsuite/gcc.dg/cpp/trad/Wunused.c

@@ -26,6 +26,12 @@
 #endif
 used4
 
+unused7;			/* This does not count as a use.  */
+
+#if 0
+unused5				/* This does not count as a use.  */
+#endif
+
 #undef unused5
 #define unused6
 unused6