From: Qu Wenruo <quwenruo.btrfs@gmx.com>
To: dsterba@suse.cz, Qu Wenruo <wqu@suse.com>,
linux-btrfs@vger.kernel.org, Su Yanjun <suyj.fnst@cn.fujitsu.com>
Subject: Re: [PATCH 2/9] btrfs-progs: fix gcc8 default build warning caused by '-Wformat-truncation'
Date: Tue, 4 Dec 2018 20:21:43 +0800 [thread overview]
Message-ID: <e65ec19d-4e02-3cb5-b85b-8bdf3b8991dd@gmx.com> (raw)
In-Reply-To: <20181204111018.GI17773@twin.jikos.cz>
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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 <suyj.fnst@cn.fujitsu.com>
>>
>> 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 <suyj.fnst@cn.fujitsu.com>
>> [Use cc-disable-warning to fix the not working CFLAGS setting in configure.ac]
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>> ---
>> 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
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next prev parent reply other threads:[~2018-12-04 12:22 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-16 7:54 [PATCH 0/9] btrfs-progs: Make W=1 clean (no "again") Qu Wenruo
2018-11-16 7:54 ` [PATCH 1/9] btrfs-progs: Makefile.extrawarn: Import cc-disable-warning Qu Wenruo
2018-12-04 11:04 ` David Sterba
2018-11-16 7:54 ` [PATCH 2/9] btrfs-progs: fix gcc8 default build warning caused by '-Wformat-truncation' Qu Wenruo
2018-12-04 11:10 ` David Sterba
2018-12-04 12:21 ` Qu Wenruo [this message]
2018-11-16 7:54 ` [PATCH 3/9] btrfs-progs: Makefile.extrawarn: Don't warn on sign compare Qu Wenruo
2018-11-16 8:00 ` [PATCH v1.1 " Qu Wenruo
2018-12-04 11:10 ` David Sterba
2018-11-16 7:54 ` [PATCH 4/9] btrfs-progs: Fix Wempty-body warning Qu Wenruo
2018-11-16 8:01 ` Nikolay Borisov
2018-11-16 7:54 ` [PATCH 5/9] btrfs-progs: Fix Wimplicit-fallthrough warning Qu Wenruo
2018-11-16 8:04 ` Nikolay Borisov
2018-11-16 8:10 ` Qu Wenruo
2018-11-16 7:54 ` [PATCH 6/9] btrfs-progs: Fix Wsuggest-attribute=format warning Qu Wenruo
2018-11-16 8:06 ` Nikolay Borisov
2018-11-16 7:54 ` [PATCH 7/9] btrfs-progs: Fix Wmaybe-uninitialized warning Qu Wenruo
2018-11-16 8:13 ` Nikolay Borisov
2018-11-16 8:16 ` Qu Wenruo
2018-11-16 8:22 ` [PATCH v1.1 " Qu Wenruo
2018-11-16 8:24 ` Nikolay Borisov
2018-12-04 12:17 ` [PATCH " David Sterba
2018-12-04 12:22 ` Adam Borowski
2018-12-04 12:42 ` Nikolay Borisov
2018-12-05 5:38 ` Qu Wenruo
2018-11-16 7:54 ` [PATCH 8/9] btrfs-progs: Fix Wtype-limits warning Qu Wenruo
2018-11-16 8:07 ` Nikolay Borisov
2018-11-16 7:54 ` [PATCH 9/9] btrfs-progs: Cleanup warning reported by -Wmissing-prototypes except free space tree Qu Wenruo
2018-11-16 8:04 ` [PATCH v1.1 9/9] btrfs-progs: Cleanup warning reported by -Wmissing-prototypes Qu Wenruo
2018-11-16 8:14 ` Nikolay Borisov
2018-12-04 12:22 ` David Sterba
2018-12-04 12:24 ` Qu Wenruo
2018-12-04 12:48 ` David Sterba
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