Treat -Wstrict-overflow as -Wstrict-overflow=2

[Ian Lance Taylor <iant at google dot com>]

Since -Wall implies -Wstrict-overflow=1, I think it makes sense to
change -Wstrict-overflow from -Wstrict-overflow=1 to
-Wstrict-overflow=2.  -Wstrict-overflow=2 warns about cases where
strict overflow is used to fold a conditional to a constant.  These
are the cases which catch people by surprise.

If nobody objects, I will check this in in a day or two.  Bootstrapped
and tested on i686-pc-linux-gnu.

Ian


2007-03-08  Ian Lance Taylor  <iant@google.com>

	* opts.c (common_handle_option): Treat -Wstrict-overflow (with no
	argument) like -Wstrict-overflow=2.
	* doc/invoke.texi (Warning Options): Update documentation.


Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi	(revision 122739)
+++ gcc/doc/invoke.texi	(working copy)
@@ -3017,17 +3017,17 @@ warning levels are defined.
 @item -Wstrict-overflow=1
 Warn about cases which are both questionable and easy to avoid.  For
 example: @code{x + 1 > x}; with @option{-fstrict-overflow}, the
-compiler will simplify this to @code{1}.  @option{-Wstrict-overflow}
-(with no level) is the same as @option{-Wstrict-overflow=1}.  This
-level of @option{-Wstrict-overflow} is enabled by @option{-Wall};
-higher levels are not, and must be explicitly requested.
+compiler will simplify this to @code{1}.  This level of
+@option{-Wstrict-overflow} is enabled by @option{-Wall}; higher levels
+are not, and must be explicitly requested.
 
 @item -Wstrict-overflow=2
 Also warn about other cases where a comparison is simplified to a
 constant.  For example: @code{abs (x) >= 0}.  This can only be
 simplified when @option{-fstrict-overflow} is in effect, because
 @code{abs (INT_MIN)} overflows to @code{INT_MIN}, which is less than
-zero.
+zero.  @option{-Wstrict-overflow} (with no level) is the same as
+@option{-Wstrict-overflow=2}.
 
 @item -Wstrict-overflow=3
 Also warn about other cases where a comparison is simplified.  For
Index: gcc/opts.c
===================================================================
--- gcc/opts.c	(revision 122739)
+++ gcc/opts.c	(working copy)
@@ -1094,6 +1094,11 @@ common_handle_option (size_t scode, cons
       break;
 
     case OPT_Wstrict_overflow:
+      warn_strict_overflow = (value
+			      ? (int) WARN_STRICT_OVERFLOW_CONDITIONAL
+			      : 0);
+      break;
+
     case OPT_Wstrict_overflow_:
       warn_strict_overflow = value;
       break;