On Thu, May 2, 2019 at 4:42 PM Bruce Richardson <bruce.richard...@intel.com> wrote:
> On Thu, May 02, 2019 at 04:24:37PM +0200, David Marchand wrote: > > On Thu, May 2, 2019 at 4:13 PM Reshma Pattan > > <[1]reshma.pat...@intel.com> wrote: > > > > gcc 9 on Fedora 30 gives an error > > "taking address of packed member may result in an > > unaligned pointer value" for -Waddress-of-packed-member. > > Report it as warning instead of error to fix the build. > > Snippet of build before fix > > ...lib/librte_eal/linux/eal/eal_memalloc.c: In function > > ‘alloc_seg_walk’: > > ...lib/librte_eal/linux/eal/eal_memalloc.c:768:12: error: taking > > address > > of packed member of ‘struct rte_mem_config’ may result in an > > unaligned > > pointer value [-Werror=address-of-packed-member] > > 768 | cur_msl = &mcfg->memsegs[msl_idx]; > > | ^~~~~~~~~~~~~~~~~~~~~~~ > > Snippet of build after fix > > ..lib/librte_eal/linux/eal/eal_memory.c: In function > > ‘remap_segment’: > > ..lib/librte_eal/linux/eal/eal_memory.c:685:9: warning: taking > > address > > of packed member of ‘struct rte_mem_config’ may result in an > > unaligned > > pointer value [-Waddress-of-packed-member] > > 685 | msl = &mcfg->memsegs[msl_idx]; > > Signed-off-by: Reshma Pattan <[2]reshma.pat...@intel.com> > > --- > > mk/toolchain/gcc/[3]rte.vars.mk | 4 ++++ > > 1 file changed, 4 insertions(+) > > diff --git a/mk/toolchain/gcc/[4]rte.vars.mk > > b/mk/toolchain/gcc/[5]rte.vars.mk > > index d8b99faf6..61032bbbc 100644 > > --- a/mk/toolchain/gcc/[6]rte.vars.mk > > +++ b/mk/toolchain/gcc/[7]rte.vars.mk > > @@ -87,5 +87,9 @@ WERROR_FLAGS += -Wimplicit-fallthrough=2 > > WERROR_FLAGS += -Wno-format-truncation > > endif > > +#Report "taking address of packed member may result > > +#in an unaligned pointer value" issues as warnings. > > +WERROR_FLAGS += -Wno-error=address-of-packed-member > > + > > export CC AS AR LD OBJCOPY OBJDUMP STRIP READELF > > export TOOLCHAIN_CFLAGS TOOLCHAIN_LDFLAGS TOOLCHAIN_ASFLAGS > > -- > > 2.21.0 > > > > No, you can't do this unconditionally. > > Looked at clang (in make build system) and meson (globally) and those > > completely disable the warning. > > $ git grep address-of-packed-member origin/master -- > > origin/master:config/meson.build: > '-Wno-address-of-packed-member' > > origin/master:mk/toolchain/clang/rte.vars.mk:WERROR_FLAGS += > > -Wno-address-of-packed-member > > It should be something like (untested): > > @@ -87,5 +87,10 @@ WERROR_FLAGS += -Wimplicit-fallthrough=2 > > WERROR_FLAGS += -Wno-format-truncation > > endif > > > > +# disable packed member unalign warnings > > +ifeq ($(shell test $(GCC_VERSION) -ge 90 && echo 1), 1) > > +WERROR_FLAGS += -Wno-address-of-packed-member > > +endif > > + > Actually, you should not need to check the GCC version for this. > GCC always ignores silently any warning disable flags it doesn't recognise, > only printing information about them if there is another error to report. > [This is why meson, when you ask it if the compiler supports "-Wno-foo", > will > check the flag and also the -Wfoo flag, as gcc won't report an error with > just the "no" form] > WERROR_FLAGS += -Wno-error=address-of-packed-member triggers an error. [dmarchan@dmarchan dpdk]$ make EXTRA_CFLAGS="-g -O0" O=master cc1: error: -Werror=address-of-packed-member: no option -Waddress-of-packed-member == Build lib cc1: error: -Werror=address-of-packed-member: no option -Waddress-of-packed-member == Build lib/librte_kvargs cc1: error: -Werror=address-of-packed-member: no option -Waddress-of-packed-member CC rte_kvargs.o cc1: error: -Werror=address-of-packed-member: no option -Waddress-of-packed-member make[3]: *** [rte_kvargs.o] Error 1 make[2]: *** [librte_kvargs] Error 2 make[1]: *** [lib] Error 2 make: *** [all] Error 2 WERROR_FLAGS += -Wno-address-of-packed-member is ignored. Marvellous :-) Sorry for the noise, let's go with your initial patch. -- David Marchand
