invoke.texi (-Wshadow=global, [...]): Fix description.

2019-10-04  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * doc/invoke.texi (-Wshadow=global, -Wshadow=local,
        -Wshadow=compatible-local): Fix description.
        Add an example where -Wshadow=compatible-local does not
        warn.

From-SVN: r276561

gcc/ChangeLog

+2019-10-04  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	* doc/invoke.texi (-Wshadow=global, -Wshadow=local,
+	-Wshadow=compatible-local): Fix description.
+	Add an example where -Wshadow=compatible-local does not
+	warn.
+
 2019-10-03  John David Anglin  <danglin@gcc.gnu.org>
 
 	* config/pa/pa.h (MAX_PCREL17F_OFFSET): Adjust.

gcc/doc/invoke.texi

@@ -6477,13 +6477,14 @@ Do not warn whenever a local variable shadows an instance variable in an
 Objective-C method.
 
 @item -Wshadow=global
-@opindex Wshadow=local
+@opindex Wshadow=global
 The default for @option{-Wshadow}. Warns for any (global) shadowing.
+This warning is enabled by @option{-Wshadow=global}.
 
 @item -Wshadow=local
 @opindex Wshadow=local
 Warn when a local variable shadows another local variable or parameter.
-This warning is enabled by @option{-Wshadow=global}.
+This warning is enabled by @option{-Wshadow=local}.
 
 @item -Wshadow=compatible-local
 @opindex Wshadow=compatible-local
@@ -6515,8 +6516,10 @@ in place of the other, type checking will catch that and emit an error or
 warning. So not warning (about shadowing) in this case will not lead to
 undetected bugs. Use of this flag instead of @option{-Wshadow=local} can
 possibly reduce the number of warnings triggered by intentional shadowing.
+Note that this does also mean that shadowing @code{const char *i} by
+@code{char *i} will not emit a warning.
 
-This warning is enabled by @option{-Wshadow=local}.
+This warning is enabled by @option{-Wshadow=compatible-local}.
 
 @item -Wlarger-than=@var{byte-size}
 @opindex Wlarger-than=