[PATCH v2] Drop more useless casts from void * to pointer

Markus Armbruster posted 1 patch 2 weeks, 1 day ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20221123133811.1398562-1-armbru@redhat.com
Maintainers: Warner Losh <imp@bsdimp.com>, Kyle Evans <kevans@freebsd.org>, "Alex Bennée" <alex.bennee@linaro.org>, Alexandre Iooss <erdnaxe@crans.org>, Mahmoud Mandour <ma.mandourr@gmail.com>, Raphael Norwitz <raphael.norwitz@nutanix.com>, "Michael S. Tsirkin" <mst@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, "Daniel P. Berrangé" <berrange@redhat.com>, Eduardo Habkost <eduardo@habkost.net>, Luc Michel <luc@lmichel.fr>, Damien Hedde <damien.hedde@greensocs.com>, "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, Alistair Francis <alistair@alistair23.me>, Peter Maydell <peter.maydell@linaro.org>, Jason Wang <jasowang@redhat.com>, Keith Busch <kbusch@kernel.org>, Klaus Jensen <its@irrelevant.dk>, Yuval Shaia <yuval.shaia.ml@gmail.com>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Eric Auger <eric.auger@redhat.com>, Laurent Vivier <laurent@vivier.eu>, Wenchao Wang <wenchao.wang@intel.com>
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(-)
[PATCH v2] Drop more useless casts from void * to pointer
Posted by Markus Armbruster 2 weeks, 1 day ago
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Laurent Vivier <laurent@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];
                 if (!pag) {
                     pag = g_try_malloc0(TARGET_PAGE_SIZE);
                     page[p / TARGET_PAGE_SIZE] = pag;
diff --git a/contrib/plugins/cache.c b/contrib/plugins/cache.c
index ac1510aaa1..2e25184a7f 100644
--- a/contrib/plugins/cache.c
+++ b/contrib/plugins/cache.c
@@ -405,7 +405,7 @@ static void vcpu_mem_access(unsigned int vcpu_index, qemu_plugin_meminfo_t info,
     g_mutex_lock(&l1_dcache_locks[cache_idx]);
     hit_in_l1 = access_cache(l1_dcaches[cache_idx], effective_addr);
     if (!hit_in_l1) {
-        insn = (InsnData *) userdata;
+        insn = userdata;
         __atomic_fetch_add(&insn->l1_dmisses, 1, __ATOMIC_SEQ_CST);
         l1_dcaches[cache_idx]->misses++;
     }
@@ -419,7 +419,7 @@ static void vcpu_mem_access(unsigned int vcpu_index, qemu_plugin_meminfo_t info,
 
     g_mutex_lock(&l2_ucache_locks[cache_idx]);
     if (!access_cache(l2_ucaches[cache_idx], effective_addr)) {
-        insn = (InsnData *) userdata;
+        insn = userdata;
         __atomic_fetch_add(&insn->l2_misses, 1, __ATOMIC_SEQ_CST);
         l2_ucaches[cache_idx]->misses++;
     }
@@ -440,7 +440,7 @@ static void vcpu_insn_exec(unsigned int vcpu_index, void *userdata)
     g_mutex_lock(&l1_icache_locks[cache_idx]);
     hit_in_l1 = access_cache(l1_icaches[cache_idx], insn_addr);
     if (!hit_in_l1) {
-        insn = (InsnData *) userdata;
+        insn = userdata;
         __atomic_fetch_add(&insn->l1_imisses, 1, __ATOMIC_SEQ_CST);
         l1_icaches[cache_idx]->misses++;
     }
@@ -454,7 +454,7 @@ static void vcpu_insn_exec(unsigned int vcpu_index, void *userdata)
 
     g_mutex_lock(&l2_ucache_locks[cache_idx]);
     if (!access_cache(l2_ucaches[cache_idx], insn_addr)) {
-        insn = (InsnData *) userdata;
+        insn = userdata;
         __atomic_fetch_add(&insn->l2_misses, 1, __ATOMIC_SEQ_CST);
         l2_ucaches[cache_idx]->misses++;
     }
diff --git a/contrib/vhost-user-blk/vhost-user-blk.c b/contrib/vhost-user-blk/vhost-user-blk.c
index d6932a2645..aa99877fcd 100644
--- a/contrib/vhost-user-blk/vhost-user-blk.c
+++ b/contrib/vhost-user-blk/vhost-user-blk.c
@@ -193,7 +193,7 @@ vub_discard_write_zeroes(VubReq *req, struct iovec *iov, uint32_t iovcnt,
 
     #if defined(__linux__) && defined(BLKDISCARD) && defined(BLKZEROOUT)
     VubDev *vdev_blk = req->vdev_blk;
-    desc = (struct virtio_blk_discard_write_zeroes *)buf;
+    desc = buf;
     uint64_t range[2] = { le64toh(desc->sector) << 9,
                           le32toh(desc->num_sectors) << 9 };
     if (type == VIRTIO_BLK_T_DISCARD) {
diff --git a/hw/core/qdev-clock.c b/hw/core/qdev-clock.c
index 117f4c6ea4..82799577f3 100644
--- a/hw/core/qdev-clock.c
+++ b/hw/core/qdev-clock.c
@@ -134,7 +134,7 @@ void qdev_init_clocks(DeviceState *dev, const ClockPortInitArray clocks)
         Clock **clkp;
         /* offset cannot be inside the DeviceState part */
         assert(elem->offset > sizeof(DeviceState));
-        clkp = (Clock **)(((void *) dev) + elem->offset);
+        clkp = ((void *)dev) + elem->offset;
         if (elem->is_output) {
             *clkp = qdev_init_clock_out(dev, elem->name);
         } else {
diff --git a/hw/hyperv/vmbus.c b/hw/hyperv/vmbus.c
index 30bc04e1c4..f956381cc9 100644
--- a/hw/hyperv/vmbus.c
+++ b/hw/hyperv/vmbus.c
@@ -2104,7 +2104,7 @@ static void process_message(VMBus *vmbus)
         goto out;
     }
     msgdata = hv_msg->payload;
-    msg = (struct vmbus_message_header *)msgdata;
+    msg = msgdata;
 
     trace_vmbus_process_incoming_message(msg->message_type);
 
diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c
index 24b3a0ff66..42ea2411a2 100644
--- a/hw/net/cadence_gem.c
+++ b/hw/net/cadence_gem.c
@@ -1429,7 +1429,7 @@ static uint64_t gem_read(void *opaque, hwaddr offset, unsigned size)
 {
     CadenceGEMState *s;
     uint32_t retval;
-    s = (CadenceGEMState *)opaque;
+    s = opaque;
 
     offset >>= 2;
     retval = s->regs[offset];
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index aba12759d5..fea6f43429 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -2472,7 +2472,7 @@ static size_t virtio_net_rsc_receive6(void *opq, NetClientState *nc,
     VirtioNetRscChain *chain;
     VirtioNetRscUnit unit;
 
-    chain = (VirtioNetRscChain *)opq;
+    chain = opq;
     hdr_len = ((VirtIONet *)(chain->n))->guest_hdr_len;
 
     if (size < (hdr_len + sizeof(struct eth_header) + sizeof(struct ip6_header)
diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
index ac3885ce50..d0684da9fe 100644
--- a/hw/nvme/ctrl.c
+++ b/hw/nvme/ctrl.c
@@ -4104,14 +4104,14 @@ static uint16_t nvme_zone_mgmt_recv(NvmeCtrl *n, NvmeRequest *req)
             nr_zones++;
         }
     }
-    header = (NvmeZoneReportHeader *)buf;
+    header = buf;
     header->nr_zones = cpu_to_le64(nr_zones);
 
     buf_p = buf + sizeof(NvmeZoneReportHeader);
     for (; zone_idx < ns->num_zones && max_zones > 0; zone_idx++) {
         zone = &ns->zone_array[zone_idx];
         if (nvme_zone_matches_filter(zrasf, zone)) {
-            z = (NvmeZoneDescr *)buf_p;
+            z = buf_p;
             buf_p += sizeof(NvmeZoneDescr);
 
             z->zt = zone->d.zt;
diff --git a/hw/rdma/vmw/pvrdma_cmd.c b/hw/rdma/vmw/pvrdma_cmd.c
index da7ddfa548..f5b6c3d728 100644
--- a/hw/rdma/vmw/pvrdma_cmd.c
+++ b/hw/rdma/vmw/pvrdma_cmd.c
@@ -269,8 +269,7 @@ static int create_cq_ring(PCIDevice *pci_dev , PvrdmaRing **ring,
     r = g_malloc(sizeof(*r));
     *ring = r;
 
-    r->ring_state = (PvrdmaRingState *)
-        rdma_pci_dma_map(pci_dev, tbl[0], TARGET_PAGE_SIZE);
+    r->ring_state = rdma_pci_dma_map(pci_dev, tbl[0], TARGET_PAGE_SIZE);
 
     if (!r->ring_state) {
         rdma_error_report("Failed to map to CQ ring state");
@@ -405,8 +404,7 @@ static int create_qp_rings(PCIDevice *pci_dev, uint64_t pdir_dma,
     *rings = sr;
 
     /* Create send ring */
-    sr->ring_state = (PvrdmaRingState *)
-        rdma_pci_dma_map(pci_dev, tbl[0], TARGET_PAGE_SIZE);
+    sr->ring_state = rdma_pci_dma_map(pci_dev, tbl[0], TARGET_PAGE_SIZE);
     if (!sr->ring_state) {
         rdma_error_report("Failed to map to QP ring state");
         goto out_free_sr_mem;
@@ -646,8 +644,7 @@ static int create_srq_ring(PCIDevice *pci_dev, PvrdmaRing **ring,
     r = g_malloc(sizeof(*r));
     *ring = r;
 
-    r->ring_state = (PvrdmaRingState *)
-            rdma_pci_dma_map(pci_dev, tbl[0], TARGET_PAGE_SIZE);
+    r->ring_state = rdma_pci_dma_map(pci_dev, tbl[0], TARGET_PAGE_SIZE);
     if (!r->ring_state) {
         rdma_error_report("Failed to map tp SRQ ring state");
         goto out_free_ring_mem;
diff --git a/hw/rdma/vmw/pvrdma_qp_ops.c b/hw/rdma/vmw/pvrdma_qp_ops.c
index bd7cbf2bdf..c30c8344f6 100644
--- a/hw/rdma/vmw/pvrdma_qp_ops.c
+++ b/hw/rdma/vmw/pvrdma_qp_ops.c
@@ -149,7 +149,7 @@ void pvrdma_qp_send(PVRDMADev *dev, uint32_t qp_handle)
 
     ring = (PvrdmaRing *)qp->opaque;
 
-    wqe = (struct PvrdmaSqWqe *)pvrdma_ring_next_elem_read(ring);
+    wqe = pvrdma_ring_next_elem_read(ring);
     while (wqe) {
         CompHandlerCtx *comp_ctx;
 
@@ -212,7 +212,7 @@ void pvrdma_qp_recv(PVRDMADev *dev, uint32_t qp_handle)
 
     ring = &((PvrdmaRing *)qp->opaque)[1];
 
-    wqe = (struct PvrdmaRqWqe *)pvrdma_ring_next_elem_read(ring);
+    wqe = pvrdma_ring_next_elem_read(ring);
     while (wqe) {
         CompHandlerCtx *comp_ctx;
 
@@ -254,7 +254,7 @@ void pvrdma_srq_recv(PVRDMADev *dev, uint32_t srq_handle)
 
     ring = (PvrdmaRing *)srq->opaque;
 
-    wqe = (struct PvrdmaRqWqe *)pvrdma_ring_next_elem_read(ring);
+    wqe = pvrdma_ring_next_elem_read(ring);
     while (wqe) {
         CompHandlerCtx *comp_ctx;
 
diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c
index 62e07ec2e4..23c470977e 100644
--- a/hw/virtio/virtio-iommu.c
+++ b/hw/virtio/virtio-iommu.c
@@ -775,8 +775,7 @@ static void virtio_iommu_handle_command(VirtIODevice *vdev, VirtQueue *vq)
             output_size = s->config.probe_size + sizeof(tail);
             buf = g_malloc0(output_size);
 
-            ptail = (struct virtio_iommu_req_tail *)
-                        (buf + s->config.probe_size);
+            ptail = buf + s->config.probe_size;
             ptail->status = virtio_iommu_handle_probe(s, iov, iov_cnt, buf);
             break;
         }
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 24b25759be..1f8c10f8ef 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -5471,7 +5471,7 @@ static abi_long do_ioctl_rt(const IOCTLEntry *ie, uint8_t *buf_temp,
     for (i = 0; i < se->nb_fields; i++) {
         if (dst_offsets[i] == offsetof(struct rtentry, rt_dev)) {
             assert(*field_types == TYPE_PTRVOID);
-            target_rt_dev_ptr = (abi_ulong *)(argptr + src_offsets[i]);
+            target_rt_dev_ptr = argptr + src_offsets[i];
             host_rt_dev_ptr = (unsigned long *)(buf_temp + dst_offsets[i]);
             if (*target_rt_dev_ptr != 0) {
                 *host_rt_dev_ptr = (unsigned long)lock_user_string(
diff --git a/target/i386/hax/hax-all.c b/target/i386/hax/hax-all.c
index b185ee8de4..b7fb5385b2 100644
--- a/target/i386/hax/hax-all.c
+++ b/target/i386/hax/hax-all.c
@@ -388,7 +388,7 @@ static int hax_handle_io(CPUArchState *env, uint32_t df, uint16_t port,
     MemTxAttrs attrs = { 0 };
 
     if (!df) {
-        ptr = (uint8_t *) buffer;
+        ptr = buffer;
     } else {
         ptr = buffer + size * count - size;
     }
diff --git a/tests/tcg/aarch64/system/semiheap.c b/tests/tcg/aarch64/system/semiheap.c
index a254bd8982..693a1b037d 100644
--- a/tests/tcg/aarch64/system/semiheap.c
+++ b/tests/tcg/aarch64/system/semiheap.c
@@ -73,11 +73,11 @@ int main(int argc, char *argv[argc])
     ml_printf("stack: %p <- %p\n", info.stack_limit, info.stack_base);
 
     /* finally can we read/write the heap */
-    ptr_to_heap = (uint32_t *) info.heap_base;
+    ptr_to_heap = info.heap_base;
     for (i = 0; i < 512; i++) {
         *ptr_to_heap++ = i;
     }
-    ptr_to_heap = (uint32_t *) info.heap_base;
+    ptr_to_heap = info.heap_base;
     for (i = 0; i < 512; i++) {
         uint32_t tmp = *ptr_to_heap;
         if (tmp != i) {
diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
index 0d1520caac..7a84b1d806 100644
--- a/util/vfio-helpers.c
+++ b/util/vfio-helpers.c
@@ -271,7 +271,7 @@ static void collect_usable_iova_ranges(QEMUVFIOState *s, void *buf)
         if (!cap->next) {
             return;
         }
-        cap = (struct vfio_info_cap_header *)(buf + cap->next);
+        cap = buf + cap->next;
     }
 
     cap_iova_range = (struct vfio_iommu_type1_info_cap_iova_range *)cap;
-- 
2.37.3
Re: [PATCH v2] Drop more useless casts from void * to pointer
Posted by BALATON Zoltan 2 weeks, 1 day ago
On Wed, 23 Nov 2022, Markus Armbruster wrote:
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> Reviewed-by: Laurent Vivier <laurent@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. Found some more info on this here:

https://stackoverflow.com/questions/3523145/pointer-arithmetic-for-void-pointer-in-c

Regards,
BALATON Zoltan
Re: [PATCH v2] Drop more useless casts from void * to pointer
Posted by Daniel P. Berrangé 2 weeks, 1 day ago
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 <armbru@redhat.com>
> > Reviewed-by: Laurent Vivier <laurent@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. 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.

With regards,
Daniel
-- 
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Re: [PATCH v2] Drop more useless casts from void * to pointer
Posted by Markus Armbruster 2 weeks, 1 day ago
Daniel P. Berrangé <berrange@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 <armbru@redhat.com>
>> > Reviewed-by: Laurent Vivier <laurent@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.
Re: [PATCH v2] Drop more useless casts from void * to pointer
Posted by BALATON Zoltan 2 weeks, 1 day ago
On Wed, 23 Nov 2022, Markus Armbruster wrote:
> Daniel P. Berrangé <berrange@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 <armbru@redhat.com>
>>>> Reviewed-by: Laurent Vivier <laurent@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.

You are right. Although I'm not sure what page[] counts as because it adds 
an offset to the pointer but [] is higher priority than (type) cast so it 
does not matter and that cast is not needed here then. Maybe I should be 
more attentive to details but I did not take the time to look at it more 
carefully. I did not say we should keep the cast anyway (considering only 
gcc and clang are targeted), I was just trying to understand why it might 
have been there in the first place.

Regards,
BALATON Zoltan

> 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.
>
>
Re: [PATCH v2] Drop more useless casts from void * to pointer
Posted by Markus Armbruster 2 weeks, 1 day ago
BALATON Zoltan <balaton@eik.bme.hu> writes:

> On Wed, 23 Nov 2022, Markus Armbruster wrote:
>> Daniel P. Berrangé <berrange@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 <armbru@redhat.com>
>>>>> Reviewed-by: Laurent Vivier <laurent@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.
>
> You are right. Although I'm not sure what page[] counts as because it adds an offset to the pointer but [] is higher priority than (type) cast so it 
> does not matter and that cast is not needed here then. Maybe I should be more attentive to details but I did not take the time to look at it more 
> carefully. I did not say we should keep the cast anyway (considering only gcc and clang are targeted), I was just trying to understand why it might 
> have been there in the first place.

And that's perfectly okay!