Debian Bug report logs - #520548
Add -fwrapv to CFLAGS

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Package: linux-2.6; Maintainer for linux-2.6 is (unknown);

Reported by: dann frazier <[email protected]>

Date: Fri, 20 Mar 2009 19:30:05 UTC

Severity: important

Tags: patch

Found in version 2.6.26-13lenny2

Fixed in version linux-2.6/2.6.26-14

Done: dann frazier <[email protected]>

Bug is archived. No further changes may be made.

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Date: Fri, 20 Mar 2009 13:29:30 -0600
From: dann frazier <[email protected]>
To: [email protected]
Subject: Add -fwrapv to CFLAGS
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Package: linux-2.6
Version: 2.6.26-13lenny2
Severity: important
Tags: patch

We should include this in stable updates. No ABI changes were detected
in a test build of the 686 flavor.

commit 68df3755e383e6fecf2354a67b08f92f18536594
Author: Linus Torvalds <[email protected]>
Date:   Thu Mar 19 11:10:17 2009 -0700

    Add '-fwrapv' to gcc CFLAGS
    
    This makes sure that gcc doesn't try to optimize away wrapping
    arithmetic, which the kernel occasionally uses for overflow testing, ie
    things like
    
    	if (ptr + offset < ptr)
    
    which technically is undefined for non-unsigned types. See
    
    	http://bugzilla.kernel.org/show_bug.cgi?id=12597
    
    for details.
    
    Not all versions of gcc support it, so we need to make it conditional
    (it looks like it was introduced in gcc-3.4).
    
    Reminded-by: Alan Cox <[email protected]>
    Signed-off-by: Linus Torvalds <[email protected]>

Adjusted to apply to Debian's 2.6.26 by dann frazier <[email protected]>

diff -urpN linux-source-2.6.26.orig/Makefile linux-source-2.6.26/Makefile
--- linux-source-2.6.26.orig/Makefile	2009-03-09 16:22:35.000000000 -0600
+++ linux-source-2.6.26/Makefile	2009-03-20 11:14:43.000000000 -0600
@@ -321,6 +321,7 @@ KBUILD_CPPFLAGS := -D__KERNEL__ $(LINUXI
 KBUILD_CFLAGS   := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
 		   -fno-strict-aliasing -fno-common \
 		   -Werror-implicit-function-declaration
+KBUILD_CFLAGS	+= $(call cc-option,-fwrapv)
 KBUILD_AFLAGS   := -D__ASSEMBLY__
 
 # Read KERNELRELEASE from include/config/kernel.release (if it exists)

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