On 2018/10/26 上午9:58, Su Yanjun wrote:
> 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);
> ^~ ~~~~
As long as we're using snprintf(), we expect some string to be
truncated, so it's not a problem at all.
> 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 <suyj.fnst@xxxxxxxxxxxxxx>
Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>
Thanks,
Qu
> ---
> Makefile.extrawarn | 1 +
> configure.ac | 2 +-
> 2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile.extrawarn b/Makefile.extrawarn
> index 1f4bda94a167..ed76fb5b5554 100644
> --- a/Makefile.extrawarn
> +++ b/Makefile.extrawarn
> @@ -47,6 +47,7 @@ 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 += $(call cc-option, -Wformat-truncation)
>
> warning-2 := -Waggregate-return
> warning-2 += -Wcast-align
> diff --git a/configure.ac b/configure.ac
> index df02f20655d9..c626beca8b77 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -12,7 +12,7 @@ LIBBTRFS_MAJOR=0
> LIBBTRFS_MINOR=1
> LIBBTRFS_PATCHLEVEL=2
>
> -CFLAGS=${CFLAGS:-"-g -O1 -Wall -D_FORTIFY_SOURCE=2"}
> +CFLAGS=${CFLAGS:-"-g -O1 -Wall -D_FORTIFY_SOURCE=2 -Wno-format-truncation"}
> AC_SUBST([CFLAGS])
>
> AC_PREREQ([2.60])
>
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