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Linus Torvalds adf96e6f51 sysrq: don't depend on weak undefined arrays to have an address that compares as NULL 
When taking an address of an extern array, gcc quite naturally should be
able to say "an address of an object can never be NULL" and just
optimize away the test entirely.

However, the new alternate sysrq reset code (commit 154b7a489a:
"Input: sysrq - allow specifying alternate reset sequence") did exactly
that, and declared platform_sysrq_reset_seq[] as a weak array, and
expecting that testing the address of the array would show whether it
actually got linked against something or not.

And that doesn't work with all gcc versions.  Clearly it works with
*some* versions of gcc, and maybe it's even supposed to work, but it
really is a very fragile concept.

So instead of testing the address of the weak variable, just create a
weak instance of that array that is empty.  If some platform then has a
real platform_sysrq_reset_seq[] that overrides our weak one, the linker
will switch to that one, and it all works without any run-time
conditionals at all.

Reported-by: Dave Airlie <airlied@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-27 09:59:50 -08:00
..
accessibility
acpi ACPI and power management fixes for 3.9-rc1 2013-02-25 21:25:17 -08:00
amba
ata 1) apply, and then revert, the sysfs export of ATA host controller number. 2013-02-24 17:32:15 -08:00
atm
auxdisplay
base Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
bcma Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless 2013-02-14 14:23:33 -05:00
block Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
bluetooth Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-02-21 17:40:58 -08:00
bus
cdrom
char Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
clk arm-soc: device tree conversions 2013-02-21 15:38:49 -08:00
clocksource Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-26 19:43:20 -08:00
connector net: proc: change proc_net_remove to remove_proc_entry 2013-02-18 14:53:08 -05:00
cpufreq ACPI and power management fixes for 3.9-rc1 2013-02-25 21:25:17 -08:00
cpuidle arm-soc: soc-specific updates 2013-02-21 15:27:22 -08:00
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2013-02-25 15:56:15 -08:00
dca
devfreq
dio
dma Merge branch 'next' of git://git.infradead.org/users/vkoul/slave-dma 2013-02-26 09:24:48 -08:00
edac Driver core patches for 3.9-rc1 2013-02-21 12:05:51 -08:00
eisa
extcon Char/Misc driver patches for 3.9-rc1 2013-02-21 13:57:13 -08:00
firewire Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-02-21 17:40:58 -08:00
firmware memory-hotplug: remove /sys/firmware/memmap/X sysfs 2013-02-23 17:50:12 -08:00
gpio GPIO changes for Linux 3.9 2013-02-26 09:35:29 -08:00
gpu Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
hid Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
hsi
hv Char/Misc driver patches for 3.9-rc1 2013-02-21 13:57:13 -08:00
hwmon ACPI and power management updates for 3.9-rc1 2013-02-20 11:26:56 -08:00
hwspinlock
i2c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
ide Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
idle Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-22 19:25:09 -08:00
iio Staging tree update for 3.9-rc1 2013-02-21 12:11:44 -08:00
infiniband Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
input This is the MFD pull request for the 3.9 merge window. 2013-02-24 20:00:58 -08:00
iommu Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
ipack Char/Misc driver patches for 3.9-rc1 2013-02-21 13:57:13 -08:00
irqchip arm-soc: cleanups 2013-02-21 14:58:40 -08:00
isdn Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
leds Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/cooloney/linux-leds 2013-02-26 09:29:02 -08:00
lguest All trivial, thanks to the stuff which didn't quite make it time. 2013-02-26 14:49:12 -08:00
macintosh Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2013-02-23 17:09:55 -08:00
mailbox
md Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
media Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
memory
memstick This is the MFD pull request for the 3.9 merge window. 2013-02-24 20:00:58 -08:00
message
mfd This is the MFD pull request for the 3.9 merge window. 2013-02-24 20:00:58 -08:00
misc Merge branch 'i2c/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2013-02-26 09:41:53 -08:00
mmc MMC highlights for 3.9: 2013-02-26 09:31:09 -08:00
mtd Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
net Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
nfc Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-next into for-davem 2013-02-18 13:47:13 -05:00
ntb
nubus
of Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-02-21 17:40:58 -08:00
oprofile oprofilefs: add missing ->i_mutex locking in object creation 2013-02-22 23:31:38 -05:00
parisc Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
parport Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2013-02-21 17:54:03 -08:00
pci Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
pcmcia Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-02-21 17:40:58 -08:00
pinctrl arm-soc: device tree conversions 2013-02-21 15:38:49 -08:00
platform Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
pnp Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
power Staging tree update for 3.9-rc1 2013-02-21 12:11:44 -08:00
pps
ps3
ptp
pwm pwm: Changes for v3.9-rc1 2013-02-26 09:34:29 -08:00
rapidio
regulator Merge remote-tracking branch 'regulator/topic/tps65090' into regulator-next 2013-02-19 12:43:12 +00:00
remoteproc All trivial, thanks to the stuff which didn't quite make it time. 2013-02-26 14:49:12 -08:00
rpmsg Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-02-21 17:40:58 -08:00
rtc This is the MFD pull request for the 3.9 merge window. 2013-02-24 20:00:58 -08:00
s390 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
sbus Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
scsi Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
sfi
sh
sn
spi arm-soc: soc-specific updates 2013-02-21 15:27:22 -08:00
ssb Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless 2013-02-14 14:23:33 -05:00
staging Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
target Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
tc
thermal
tty sysrq: don't depend on weak undefined arrays to have an address that compares as NULL 2013-02-27 09:59:50 -08:00
uio uio: remove !S390 dependency from Kconfig 2013-02-14 15:55:18 +01:00
usb Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
uwb
vfio drivers/vfio: remove depends on CONFIG_EXPERIMENTAL 2013-02-24 09:59:44 -07:00
vhost Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending 2013-02-26 11:42:23 -08:00
video Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
virt
virtio All trivial, thanks to the stuff which didn't quite make it time. 2013-02-26 14:49:12 -08:00
vlynq
vme vme: add missing put_device() after device_register() fails 2013-02-14 09:24:14 -08:00
w1 Char/Misc driver patches for 3.9-rc1 2013-02-21 13:57:13 -08:00
watchdog Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
xen Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
zorro new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
Kconfig Char/Misc driver patches for 3.9-rc1 2013-02-21 13:57:13 -08:00
Makefile Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2013-02-23 17:09:55 -08:00