linux-kernel - Re: sound/firewire/amdtp-stream.c:1099 process_rx_packets() error: uninitialized symbol 'curr_cycle

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Message-ID: <87o7ks2is9.wl-tiwai@suse.de>
Date:   Tue, 04 Jul 2023 10:16:38 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Dan Carpenter <dan.carpenter@...aro.org>
Cc:     oe-kbuild@...ts.linux.dev,
        Takashi Sakamoto <o-takashi@...amocchi.jp>, lkp@...el.com,
        oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Takashi Iwai <tiwai@...e.de>
Subject: Re: sound/firewire/amdtp-stream.c:1099 process_rx_packets() error: uninitialized symbol 'curr_cycle_time'.

On Mon, 03 Jul 2023 15:00:01 +0200,
Dan Carpenter wrote:
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   b25f62ccb490680a8cee755ac4528909395e0711
> commit: fef4e61b0b765b6d22badcd5b6575b159e7d510a ALSA: firewire-lib: extend tracepoints event including CYCLE_TIME of 1394 OHCI
> config: i386-randconfig-m021-20230701 (https://download.01.org/0day-ci/archive/20230701/202307011324.jFJ96dTo-lkp@intel.com/config)
> compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
> reproduce: (https://download.01.org/0day-ci/archive/20230701/202307011324.jFJ96dTo-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> | Closes: https://lore.kernel.org/r/202307011324.jFJ96dTo-lkp@intel.com/
> 
> New smatch warnings:
> sound/firewire/amdtp-stream.c:1099 process_rx_packets() error: uninitialized symbol 'curr_cycle_time'.
> 
> Old smatch warnings:
> sound/firewire/amdtp-stream.c:944 generate_tx_packet_descs() error: uninitialized symbol 'curr_cycle_time'.
(snip)
> The curr_cycle_time variable is only going to be used if trace_amdtp_packet_enabled()
> is true.  We would consider it a false positive if build_it_pkt_header()
> is inlined but a bug if it's not.  (Technically passing uninitialized
> data is undefined behavior but if a function is inlined then it's not
> "passing" anything).

Yes, this is a false-positive, so no much worry needed.  But it's hard
for compiler / checker to know it, and I guess that simply
initializing the variable would be the easiest workaround, after all.


thanks,

Takashi