| Message ID | 20161216105634.235457-12-arnd@arndb.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Dec 16, 2016 at 2:56 AM, Arnd Bergmann <arnd@arndb.de> wrote: > > With arm-linux-gcc-4.2, almost every file we build in the kernel ends > up with this warning: > > include/linux/fs.h:2648: warning: comparison of unsigned expression < 0 is always false > Thanks, I'd like to see this fixed as a similar warning gets printed whenever running many of the bcc/BPF tools, which gets annoying and is user-visible. eg: # /usr/share/bcc/tools/xfsslower 1 In file included from /virtual/main.c:3: /lib/modules/4.8.6-300.fc25.x86_64/build/include/linux/fs.h:2677:9: warning: comparison of unsigned enum expression < 0 is always false [-Wtautological-compare] if (id < 0 || id >= READING_MAX_ID) ~~ ^ ~ 1 warning generated. Tracing XFS operations slower than 1 ms TIME COMM PID T BYTES OFF_KB LAT(ms) FILENAME 14:44:27 cksum 4414 R 65536 0 1.02 chcon 14:44:27 cksum 4414 R 65536 0 1.20 cpio 14:44:27 cksum 4414 R 65536 0 1.01 diff 14:44:27 cksum 4414 R 65536 0 1.15 dir [...] This patch fixes the warning. Brendan > > Later versions don't have this problem, but it's easy enough to > work around. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > include/linux/fs.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 398cf20a706d..782c2a292fd7 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -2645,7 +2645,7 @@ static const char * const kernel_read_file_str[] = { > > static inline const char *kernel_read_file_id_str(enum kernel_read_file_id id) > { > - if (id < 0 || id >= READING_MAX_ID) > + if ((unsigned)id >= READING_MAX_ID) > return kernel_read_file_str[READING_UNKNOWN]; > > return kernel_read_file_str[id]; > -- > 2.9.0 > -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Jan 3, 2017 at 2:47 PM, Brendan Gregg <brendan.d.gregg@gmail.com> wrote: > > On Fri, Dec 16, 2016 at 2:56 AM, Arnd Bergmann <arnd@arndb.de> wrote: > > > > With arm-linux-gcc-4.2, almost every file we build in the kernel ends > > up with this warning: > > > > include/linux/fs.h:2648: warning: comparison of unsigned expression < 0 is always false > > > > Thanks, I'd like to see this fixed as a similar warning gets printed > whenever running many of the bcc/BPF tools, which gets annoying and is > user-visible. eg: > > # /usr/share/bcc/tools/xfsslower 1 > In file included from /virtual/main.c:3: > /lib/modules/4.8.6-300.fc25.x86_64/build/include/linux/fs.h:2677:9: > warning: comparison of unsigned enum expression < 0 is always false > [-Wtautological-compare] > if (id < 0 || id >= READING_MAX_ID) > ~~ ^ ~ > 1 warning generated. > Tracing XFS operations slower than 1 ms > TIME COMM PID T BYTES OFF_KB LAT(ms) FILENAME > 14:44:27 cksum 4414 R 65536 0 1.02 chcon > 14:44:27 cksum 4414 R 65536 0 1.20 cpio > 14:44:27 cksum 4414 R 65536 0 1.01 diff > 14:44:27 cksum 4414 R 65536 0 1.15 dir > [...] > > This patch fixes the warning. > What's the status of this patch? I still get these warnings on latest. Thanks, Brendan -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/fs.h b/include/linux/fs.h index 398cf20a706d..782c2a292fd7 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2645,7 +2645,7 @@ static const char * const kernel_read_file_str[] = { static inline const char *kernel_read_file_id_str(enum kernel_read_file_id id) { - if (id < 0 || id >= READING_MAX_ID) + if ((unsigned)id >= READING_MAX_ID) return kernel_read_file_str[READING_UNKNOWN]; return kernel_read_file_str[id];
With arm-linux-gcc-4.2, almost every file we build in the kernel ends up with this warning: include/linux/fs.h:2648: warning: comparison of unsigned expression < 0 is always false Later versions don't have this problem, but it's easy enough to work around. Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- include/linux/fs.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)