Messages in this thread | | | Subject | Re: [char-misc:char-misc-linus 3/3] drivers/misc/cardreader/rtsx_usb.c:639:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true | From | Shuah Khan <> | Date | Fri, 1 Jul 2022 10:09:45 -0600 |
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On 7/1/22 9:52 AM, Shuah Khan wrote: > On 7/1/22 9:39 AM, Nathan Chancellor wrote: >> On Fri, Jul 01, 2022 at 08:48:11AM -0600, Shuah Khan wrote: >>> On 7/1/22 2:59 AM, Greg Kroah-Hartman wrote:
>>>>> All warnings (new ones prefixed by >>): >>>>> >>>>>>> drivers/misc/cardreader/rtsx_usb.c:639:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized] >>>>> if (!ucr->rsp_buf) >>>>> ^~~~~~~~~~~~~ >>>>> drivers/misc/cardreader/rtsx_usb.c:678:9: note: uninitialized use occurs here >>>>> return ret; >>>>> ^~~ >>>>> drivers/misc/cardreader/rtsx_usb.c:639:2: note: remove the 'if' if its condition is always false >>>>> if (!ucr->rsp_buf) >>>>> ^~~~~~~~~~~~~~~~~~ >>>>> drivers/misc/cardreader/rtsx_usb.c:622:9: note: initialize the variable 'ret' to silence this warning >>>>> int ret; >>>>> ^ >>>>> = 0 >>>>> 1 warning generated. >>>> >>>> Odd, gcc doesn't show this for me. Shuah, can you send a follow-on >>>> patch to fix this? The warning does look correct. >>>> >>> >>> gcc didn't complain when I compiled either. I will send a follow-on patch. >> >> Unfortunately, GCC won't warn for most uninitialized variables by >> default after 5.7, which included commit 78a5255ffb6a ("Stop the ad-hoc >> games with -Wno-maybe-initialized"). They will potentially show up at >> W=2 or with an explicit KCFLAGS=-Wmaybe-uninitialized (it does in this >> case): >> > > Thank you. > >> | drivers/misc/cardreader/rtsx_usb.c: In function ‘rtsx_usb_probe’: >> | drivers/misc/cardreader/rtsx_usb.c:678:16: error: ‘ret’ may be used uninitialized [-Werror=maybe-uninitialized] >> | 678 | return ret; >> | | ^~~ >> | drivers/misc/cardreader/rtsx_usb.c:622:13: note: ‘ret’ was declared here >> | 622 | int ret; >> | | ^~~ >> | cc1: all warnings being treated as errors >> > > This is a bug and a good find. ret should have been set > in the if (!ucr->rsp_buf) before going to error handling. > > I wonder if it would have been flagged if ret were to be > initialized to 0. Something to experiment. >
I had to try. As I suspected initializing ret will mask this bug.
KCFLAGS=-Wmaybe-uninitialized will not flag it even though the bug still exists. It will return 0 when memory allocation fails.
Initializing isn't always the right answer for these kinds of warnings.
thanks, -- Shuah
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