On 7/3/21 10:45 AM, Peter Maydell wrote:
On Sat, 3 Jul 2021 at 15:37, Cole Robinson <crobi...@redhat.com> wrote:
Hi, I'm hitting build errors with clang on i686 userspace on x86_64
kernel. Affects both qemu 6.0.0 and qemu.git, tested with fedora
clang-12.0.1~rc3-1.fc35.i686.
Full build log from the 6.0.0 build:
https://gist.githubusercontent.com/crobinso/7b1206044eac7326490b2adce829e861/raw/9dddef968051fd6383ba7adb9e595081ad4f8fa4/gistfile1.txt
Lots of errors like:
/usr/bin/ld: libqemu-aarch64-softmmu.fa.p/accel_tcg_cputlb.c.o: in
function `helper_atomic_cmpxchgq_le_mmu':
/builddir/build/BUILD/qemu-6.0.0/accel/tcg/atomic_template.h:86:
undefined reference to `__atomic_compare_exchange_8'
/usr/bin/ld: libqemu-aarch64-softmmu.fa.p/accel_tcg_cputlb.c.o: in
function `helper_atomic_xchgq_le_mmu':
/builddir/build/BUILD/qemu-6.0.0/accel/tcg/atomic_template.h:134:
undefined reference to `__atomic_exchange_8'
Also warnings like:
/builddir/build/BUILD/qemu-6.0.0/include/qemu/stats64.h:58:21: warning:
misaligned atomic operation may incur significant performance penalty;
the expected alignment (8 bytes) exceeds the actual alignment (4 bytes)
[-Watomic-alignment]
uint64_t orig = qatomic_read__nocheck(&s->value);
^
/builddir/build/BUILD/qemu-6.0.0/include/qemu/atomic.h:129:5: note:
expanded from macro 'qatomic_read__nocheck'
__atomic_load_n(ptr, __ATOMIC_RELAXED)
I think at least part of what is happening here is that this compiler/host
doesn't support native 64-bit atomics, but configure has selected
CONFIG_ATOMIC64 anyway.
Not true. The host certainly supports it.
This is a new alignment warning in clang-12 wrt the alignment of the atomic operation.
Which may be complicated by the fact that the i386 abi does not normally align structures
beyond 4 bytes.
We may need to disable this warning for i386 (but not x86_64).
r~
