[U-Boot] [PATCH] fix: tools: kwbimage.c: Initialize headersz to suppress warning

[Guillaume Gardet]

Hi,

Le 23/11/2014 18:38, Lukasz Majewski a écrit :
> Hi Albert,
>
> Sorry for a late reply.
>
>> Hello Lukasz,
>>
>> On Sat, 22 Nov 2014 07:56:35 +0100, Lukasz Majewski
>> <l.majewski at majess.pl> wrote:
>>
>>>> Agreed in general, but not for this one, since "fixing" is the
>>>> carpet,
>>> I assume that you are presenting below an answer to a "general"
>>> case.
>>>
>>> However, as Thomas pointed out earlier, this "fix" is perfectly safe
>>> regarding the underlying kwbimage code.
>> Jeroen and I (full disclaimer: we have discussed the topic on IRC)
>> do not contend that the proposed fix would be unsafe; it *is* safe,
>> i.e. it does not adversely affect the code behavior in any measurable
>> way.
>>
>> What we contend is that the fix be the /right/ fix (although Jeroen
>> and I have slightly differing criteria for defining what "the right
>> fix" would be).
>>
>>>>> and
>>>>> the only justification I see as acceptable for doing so is when
>>>>> leaving the warning enabled would cause an obnoxiously high
>>>>> number of false positives.
>>>> Well let me add, if "fixing the warning" causes real error
>>>> to be hidden, we shouldn't "fix" the warnings by modifying
>>>> valid code.
>>> Each subsequent "fix" for this kind of warning should be considered
>>> case by case IMHO, therefore I agree with Albert.
>> Jeroen also agreed on IRC that disabling the compiler warning is not
>> the right fix either; and I agreed that there had to be a better fix
>> than pseudo-initializing headersz. I therefore suggested refactoring
>> kwbimage_set_header in order to ensure gcc does not emit the warning,
>> but without resorting to non-functional code such as a functionally
>> meaningless initialization.
>>
>> Problem is, to refactor the code, one needs a gcc which emits the
>> warnig. I tried various versions of gcc (4.7.4, 4.8.3, 4.9.1) and all
>> remained silent when compiling tools/kwbimage.c.
>>
>> Hence my request: Lukasz, which toolchain are you using exactly? Where
>> can we download it from?
> The warning appear on my personal laptop too:
>
> lukma at jawa:~/work/embedded/u-boot-denx (master)$ cc -v
> Using built-in specs.
> COLLECT_GCC=cc
> COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.7/lto-wrapper
> Target: x86_64-linux-gnu
> Configured with: ../src/configure -v --with-pkgversion='Debian 4.7.2-5'
> --with-bugurl=file:///usr/share/doc/gcc-4.7/README.Bugs
> --enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr
> --program-suffix=-4.7 --enable-shared --enable-linker-build-id
> --with-system-zlib --libexecdir=/usr/lib --without-included-gettext
> --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.7
> --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
> --enable-libstdcxx-debug --enable-libstdcxx-time=yes
> --enable-gnu-unique-object --enable-plugin --enable-objc-gc
> --with-arch-32=i586 --with-tune=generic --enable-checking=release
> --build=x86_64-linux-gnu --host=x86_64-linux-gnu
> --target=x86_64-linux-gnu Thread model: posix gcc version 4.7.2 (Debian
> 4.7.2-5)
>
>
>    HOSTCC  tools/kwbimage.o
> tools/kwbimage.c: In function ‘kwbimage_set_header’:
> tools/kwbimage.c:803:8: warning: ‘headersz’ may be used uninitialized
> in this function [-Wmaybe-uninitialized]
>
> Debian distro: version 7.6 (Wheezy)

I also have this warning on my openSUSE 13.1 (GCC 4.8.1). If it could help, "gcc -v" returns:
**********************************************************************
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib64/gcc/x86_64-suse-linux/4.8/lto-wrapper
Target: x86_64-suse-linux
Configured with: ../configure --prefix=/usr --infodir=/usr/share/info --mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64 --enable-languages=c,c++,objc,fortran,obj-c++,java,ada --enable-checking=release --with-gxx-include-dir=/usr/include/c++/4.8 --enable-ssp --disable-libssp --disable-plugin --with-bugurl=http://bugs.opensuse.org/ --with-pkgversion='SUSE Linux' --disable-libgcj --disable-libmudflap --with-slibdir=/lib64 --with-system-zlib --enable-__cxa_atexit --enable-libstdcxx-allocator=new --disable-libstdcxx-pch --enable-version-specific-runtime-libs --enable-linker-build-id --program-suffix=-4.8 --enable-linux-futex --without-system-libunwind --with-arch-32=i586 --with-tune=generic --build=x86_64-suse-linux
Thread model: posix
gcc version 4.8.1 20130909 [gcc-4_8-branch revision 202388] (SUSE Linux)
**********************************************************************



Guillaume