Re: [dpdk-dev] error: value computed is not used

["Qiu, Michael" <michael.qiu@intel.com>]

Any other comments on this issue?

Thanks,
Michael

On 12/8/2014 5:07 PM, Qiu, Michael wrote:
> Hi all,
> My platform is:
>
> uname -a
> Linux suse-11-sp3 3.0.77-0.11-xen #1 SMP Tue Mar 11 16:48:56 CST 2014
> x86_64 x86_64 x86_64 GNU/Linux
>
> gcc -v
> Using built-in specs.
> COLLECT_GCC=gcc
> COLLECT_LTO_WRAPPER=/usr/lib64/gcc/x86_64-suse-linux/4.5/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++/4.5
> --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 --program-suffix=-4.5
> --enable-linux-futex --without-system-libunwind --enable-gold
> --with-plugin-ld=/usr/bin/gold --with-arch-32=i586 --with-tune=generic
> --build=x86_64-suse-linux
> Thread model: posix
> gcc version 4.5.1 20101208 [gcc-4_5-branch revision 167585] (SUSE Linux)
>
> When I try to compile the source code to x86_64 linuxapp, I got this
> error message:
>
> lib/librte_pmd_enic/enic_main.c: In function ‘enic_set_rsskey’:
> lib/librte_pmd_enic/enic_main.c:862:2: error: value computed is not used
>
> I dig out that, it was ome issue of  the macros rte_memcpy()
> #define rte_memcpy(dst, src, n)              \
>         ((__builtin_constant_p(n)) ?          \
>         memcpy((dst), (src), (n)) :          \
>         rte_memcpy_func((dst), (src), (n)))
>
> When I use only (n) instead of (__builtin_constant_p(n), it will pass( I
> know that it was incorrect, just a experiment).
>
> But I try to use inline function instead of macros:
> static inline void * rte_memcpy(void *dst, const void *src, size_t n)
> {
>         return __builtin_constant_p(n) ? memcpy(dst, src, n) :
>                                          rte_memcpy_func(dst, src, n);
> }
>
> It will pass:), and works, this could be one potential workaround fix.
>
> Who knows why? The root cause is what?
>
> I've no idea about this.
>
> Thanks,
> Michael
>