Daniel P. Berrangé <berra...@redhat.com> writes:
> On Wed, Nov 23, 2022 at 02:51:49PM +0100, BALATON Zoltan wrote:
>> On Wed, 23 Nov 2022, Markus Armbruster wrote:
>> > Signed-off-by: Markus Armbruster <arm...@redhat.com>
>> > Reviewed-by: Laurent Vivier <laur...@vivier.eu>
>> > ---
>> > v2:
>> > * PATCH 1+2 merged as commit 0a553c12c7 and 3f7febc937
>> > * PATCH 3 change to util/coroutine-ucontext.c dropped [Laurent]
>> >
>> > bsd-user/elfload.c | 2 +-
>> > contrib/plugins/cache.c | 8 ++++----
>> > contrib/vhost-user-blk/vhost-user-blk.c | 2 +-
>> > hw/core/qdev-clock.c | 2 +-
>> > hw/hyperv/vmbus.c | 2 +-
>> > hw/net/cadence_gem.c | 2 +-
>> > hw/net/virtio-net.c | 2 +-
>> > hw/nvme/ctrl.c | 4 ++--
>> > hw/rdma/vmw/pvrdma_cmd.c | 9 +++------
>> > hw/rdma/vmw/pvrdma_qp_ops.c | 6 +++---
>> > hw/virtio/virtio-iommu.c | 3 +--
>> > linux-user/syscall.c | 2 +-
>> > target/i386/hax/hax-all.c | 2 +-
>> > tests/tcg/aarch64/system/semiheap.c | 4 ++--
>> > util/vfio-helpers.c | 2 +-
>> > 15 files changed, 24 insertions(+), 28 deletions(-)
>> >
>> > diff --git a/bsd-user/elfload.c b/bsd-user/elfload.c
>> > index f8edb22f2a..fbcdc94b96 100644
>> > --- a/bsd-user/elfload.c
>> > +++ b/bsd-user/elfload.c
>> > @@ -156,7 +156,7 @@ static abi_ulong copy_elf_strings(int argc, char
>> > **argv, void **page,
>> > --p; --tmp; --len;
>> > if (--offset < 0) {
>> > offset = p % TARGET_PAGE_SIZE;
>> > - pag = (char *)page[p / TARGET_PAGE_SIZE];
>> > + pag = page[p / TARGET_PAGE_SIZE];
>>
>> I think arithmetic on void pointer was undefined at least in the past so
>> some compilers may warn for it but not sure if this is still the case for
>> the compilers we care about. Apparently not if this now compiles but that
>> explains why this cast was not useless.
I don't think so :)
@pag is char *.
@page is void **.
page[p / TARGET_PAGE_SIZE] is void *. No need to cast to char * before
assigning to @pag.
No pointer arithmetic so far. There's some further down: pag + offset.
@pag is char * before and after my patch.
>> Found some more info on this here:
>>
>> https://stackoverflow.com/questions/3523145/pointer-arithmetic-for-void-pointer-in-c
>
> QEMU explicitly only targets GCC + Clang, so portability to other
> compilers is not required.
Correct. We do arithmentic with void * in many places already.
If we cared for portability to other compilers, we'd enable
'-Wpointer-arith'
Warn about anything that depends on the "size of" a function type
or of 'void'. GNU C assigns these types a size of 1, for
convenience in calculations with 'void *' pointers and pointers to
functions. In C++, warn also when an arithmetic operation involves
'NULL'. This warning is also enabled by '-Wpedantic'.
But we don't.
