Re: [PATCH 2/9] btrfs-progs: fix gcc8 default build warning caused by '-Wformat-truncation'
On 2018/12/4 下午7:10, David Sterba wrote: > On Fri, Nov 16, 2018 at 03:54:19PM +0800, Qu Wenruo wrote: >> From: Su Yanjun >> >> When using gcc8 compiles utils.c, it complains as below: >> >> utils.c:852:45: warning: '%s' directive output may be truncated writing >> up to 4095 bytes into a region of size 4084 [-Wformat-truncation=] >>snprintf(path, sizeof(path), "/dev/mapper/%s", name); >> ^~ >> In file included from /usr/include/stdio.h:873, >> from utils.c:20: >> /usr/include/bits/stdio2.h:67:10: note: '__builtin___snprintf_chk' >> output between 13 and 4108 bytes into a destination of size 4096 >>return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1, >> ^~~~ >> __bos (__s), __fmt, __va_arg_pack ()); >> ~ >> >> This isn't a type of warning we care about, particularly when PATH_MAX >> is much less than either. >> >> Using the GCC option -Wno-format-truncation to disable this for default >> build. >> >> Signed-off-by: Su Yanjun >> [Use cc-disable-warning to fix the not working CFLAGS setting in >> configure.ac] >> Signed-off-by: Qu Wenruo >> --- >> Makefile | 1 + >> Makefile.extrawarn | 1 + >> 2 files changed, 2 insertions(+) >> >> diff --git a/Makefile b/Makefile >> index f4ab14ea74c8..252299f8869f 100644 >> --- a/Makefile >> +++ b/Makefile >> @@ -49,6 +49,7 @@ CSCOPE_CMD := cscope -u -b -c -q >> include Makefile.extrawarn >> >> EXTRA_CFLAGS := >> +EXTRA_CFLAGS += $(call cc-disable-warning, format-truncation) > > Please don't touch EXTRA_CFLAGS, this is for users who want to override > any defaults that are set by build. This should go to CFLAGS. > >> EXTRA_LDFLAGS := >> >> DEBUG_CFLAGS_DEFAULT = -O0 -U_FORTIFY_SOURCE -ggdb3 >> diff --git a/Makefile.extrawarn b/Makefile.extrawarn >> index 5849036fd166..bbb2d5173846 100644 >> --- a/Makefile.extrawarn >> +++ b/Makefile.extrawarn >> @@ -53,6 +53,7 @@ warning-1 += -Wold-style-definition >> warning-1 += $(call cc-option, -Wmissing-include-dirs) >> warning-1 += $(call cc-option, -Wunused-but-set-variable) >> warning-1 += $(call cc-disable-warning, missing-field-initializers) >> +warning-1 += $(call cc-disable-warning, format-truncation) > > It's ok to disable for W=1 but eg. the W=3 level could take all > previously disabled warnings. Any guide on the warning disabling? IMHO the format-truncation used in any snprintf()-like functions are really more or less expected, just like missing-field-initializers. THanks, Qu > >> >> warning-2 := -Waggregate-return >> warning-2 += -Wcast-align >> -- >> 2.19.1 signature.asc Description: OpenPGP digital signature
Re: [PATCH 2/9] btrfs-progs: fix gcc8 default build warning caused by '-Wformat-truncation'
On Fri, Nov 16, 2018 at 03:54:19PM +0800, Qu Wenruo wrote: > From: Su Yanjun > > When using gcc8 compiles utils.c, it complains as below: > > utils.c:852:45: warning: '%s' directive output may be truncated writing > up to 4095 bytes into a region of size 4084 [-Wformat-truncation=] >snprintf(path, sizeof(path), "/dev/mapper/%s", name); > ^~ > In file included from /usr/include/stdio.h:873, > from utils.c:20: > /usr/include/bits/stdio2.h:67:10: note: '__builtin___snprintf_chk' > output between 13 and 4108 bytes into a destination of size 4096 >return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1, > ^~~~ > __bos (__s), __fmt, __va_arg_pack ()); > ~ > > This isn't a type of warning we care about, particularly when PATH_MAX > is much less than either. > > Using the GCC option -Wno-format-truncation to disable this for default > build. > > Signed-off-by: Su Yanjun > [Use cc-disable-warning to fix the not working CFLAGS setting in configure.ac] > Signed-off-by: Qu Wenruo > --- > Makefile | 1 + > Makefile.extrawarn | 1 + > 2 files changed, 2 insertions(+) > > diff --git a/Makefile b/Makefile > index f4ab14ea74c8..252299f8869f 100644 > --- a/Makefile > +++ b/Makefile > @@ -49,6 +49,7 @@ CSCOPE_CMD := cscope -u -b -c -q > include Makefile.extrawarn > > EXTRA_CFLAGS := > +EXTRA_CFLAGS += $(call cc-disable-warning, format-truncation) Please don't touch EXTRA_CFLAGS, this is for users who want to override any defaults that are set by build. This should go to CFLAGS. > EXTRA_LDFLAGS := > > DEBUG_CFLAGS_DEFAULT = -O0 -U_FORTIFY_SOURCE -ggdb3 > diff --git a/Makefile.extrawarn b/Makefile.extrawarn > index 5849036fd166..bbb2d5173846 100644 > --- a/Makefile.extrawarn > +++ b/Makefile.extrawarn > @@ -53,6 +53,7 @@ warning-1 += -Wold-style-definition > warning-1 += $(call cc-option, -Wmissing-include-dirs) > warning-1 += $(call cc-option, -Wunused-but-set-variable) > warning-1 += $(call cc-disable-warning, missing-field-initializers) > +warning-1 += $(call cc-disable-warning, format-truncation) It's ok to disable for W=1 but eg. the W=3 level could take all previously disabled warnings. > > warning-2 := -Waggregate-return > warning-2 += -Wcast-align > -- > 2.19.1
[PATCH 2/9] btrfs-progs: fix gcc8 default build warning caused by '-Wformat-truncation'
From: Su Yanjun When using gcc8 compiles utils.c, it complains as below: utils.c:852:45: warning: '%s' directive output may be truncated writing up to 4095 bytes into a region of size 4084 [-Wformat-truncation=] snprintf(path, sizeof(path), "/dev/mapper/%s", name); ^~ In file included from /usr/include/stdio.h:873, from utils.c:20: /usr/include/bits/stdio2.h:67:10: note: '__builtin___snprintf_chk' output between 13 and 4108 bytes into a destination of size 4096 return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1, ^~~~ __bos (__s), __fmt, __va_arg_pack ()); ~ This isn't a type of warning we care about, particularly when PATH_MAX is much less than either. Using the GCC option -Wno-format-truncation to disable this for default build. Signed-off-by: Su Yanjun [Use cc-disable-warning to fix the not working CFLAGS setting in configure.ac] Signed-off-by: Qu Wenruo --- Makefile | 1 + Makefile.extrawarn | 1 + 2 files changed, 2 insertions(+) diff --git a/Makefile b/Makefile index f4ab14ea74c8..252299f8869f 100644 --- a/Makefile +++ b/Makefile @@ -49,6 +49,7 @@ CSCOPE_CMD := cscope -u -b -c -q include Makefile.extrawarn EXTRA_CFLAGS := +EXTRA_CFLAGS += $(call cc-disable-warning, format-truncation) EXTRA_LDFLAGS := DEBUG_CFLAGS_DEFAULT = -O0 -U_FORTIFY_SOURCE -ggdb3 diff --git a/Makefile.extrawarn b/Makefile.extrawarn index 5849036fd166..bbb2d5173846 100644 --- a/Makefile.extrawarn +++ b/Makefile.extrawarn @@ -53,6 +53,7 @@ warning-1 += -Wold-style-definition warning-1 += $(call cc-option, -Wmissing-include-dirs) warning-1 += $(call cc-option, -Wunused-but-set-variable) warning-1 += $(call cc-disable-warning, missing-field-initializers) +warning-1 += $(call cc-disable-warning, format-truncation) warning-2 := -Waggregate-return warning-2 += -Wcast-align -- 2.19.1
