On Tue, Dec 19, 2017 at 07:01:44PM +0100, Michael Weiser wrote:
> Hi Kyrill,
>
> On Tue, Dec 19, 2017 at 05:35:03PM +0000, Kyrill Tkachov wrote:
>
> > > below patch fixes PR 83492.
> > I agree with your analysis of the bug and your patch will fix the
> > problem when compiling with GCC. However, I believe the more
> > appropriate macro to check here is __ARM_BIG_ENDIAN as that
> > is the macro defined by the ACLE specification [1].
>
> > __AARCH64EB__ is indeed defined by aarch64 GCC when compiling
> > for big-endian but I don't think it's standardised and may in theory
> > not be defined by other host compilers the user may use to compile GCC.
>
> Since the macro is used in various places around the code, I'd suggest
> fixing this bug and getting back in line with the rest of the codebase
> by applying my patch as-is. The move towards a more appropriate macro to
> base the checks on can then be done in a separate step using
> search'n'replace.
>
> $ grep -r __AARCH64EB__ . | cut -d: -f1 | sort -u | grep -v \.svn
> ./gcc/config/aarch64/aarch64-c.c
> ./gcc/config/aarch64/arm_neon.h
> ./gcc/testsuite/lib/target-supports.exp
> ./libcpp/ChangeLog
> ./libcpp/lex.c
> ./libffi/src/aarch64/ffi.c
> ./libffi/src/aarch64/sysv.S
> ./libgcc/config/aarch64/linux-unwind.h
> ./libgcc/config/aarch64/sfp-machine.h
> ./libstdc++-v3/config/cpu/aarch64/opt/ext/opt_random.h
That doesn't tell anything on what should be used in libcpp. Unlike the
rest, libcpp is a library that needs to be built on the host, with the
host compiler (which doesn't have to be GCC). The only case that is in
the same category is opt_random.h, because it is an installed header and
so again, can be used by GCC or other compilers.
GCC isn't going to stop defining __AARCH64EB__ nor __ARM_BIG_ENDIAN,
it is purely about other compilers.
Jakub
