Re: [Xen-devel] [PATCH v2 1/2] misc: Replace zero-length arrays with flexible array member (automatic)
On Wed, Mar 04, 2020 at 04:38:15PM +0100, Philippe Mathieu-Daudé wrote:
> Description copied from Linux kernel commit from Gustavo A. R. Silva
> (see [3]):
>
> --v-- description start --v--
>
> The current codebase makes use of the zero-length array language
> extension to the C90 standard, but the preferred mechanism to
> declare variable-length types such as these ones is a flexible
> array member [1], introduced in C99:
>
> struct foo {
> int stuff;
> struct boo array[];
> };
>
> By making use of the mechanism above, we will get a compiler
> warning in case the flexible array does not occur last in the
> structure, which will help us prevent some kind of undefined
> behavior bugs from being unadvertenly introduced [2] to the
> Linux codebase from now on.
>
> --^-- description end --^--
>
> Do the similar housekeeping in the QEMU codebase (which uses
> C99 since commit 7be41675f7cb).
>
> All these instances of code were found with the help of the
> following Coccinelle script:
>
> @@
> identifier s, m, a;
> type t, T;
> @@
>struct s {
> ...
> t m;
> - T a[0];
> + T a[];
> };
> @@
> identifier s, m, a;
> type t, T;
> @@
>struct s {
> ...
> t m;
> - T a[0];
> + T a[];
>} QEMU_PACKED;
>
> [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
> [2]
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=76497732932f
> [3]
> https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/commit/?id=17642a2fbd2c1
>
> Inspired-by: Gustavo A. R. Silva
> Reviewed-by: David Hildenbrand
> Signed-off-by: Philippe Mathieu-Daudé
Acked-by: Michael S. Tsirkin
Reviewed-by: Michael S. Tsirkin
> ---
> v2: cocci script updated to not match structures of onlyi
> a single flexible array member:
>
> block/qed.h:106:14: error: flexible array member 'offsets' not allowed in
> otherwise empty struct
> uint64_t offsets[]; /* in bytes */
>^
> ---
> bsd-user/qemu.h | 2 +-
> contrib/libvhost-user/libvhost-user.h | 2 +-
> hw/m68k/bootinfo.h| 2 +-
> hw/scsi/srp.h | 6 +++---
> hw/xen/xen_pt.h | 2 +-
> include/hw/acpi/acpi-defs.h | 12 ++--
> include/hw/arm/smmu-common.h | 2 +-
> include/hw/i386/intel_iommu.h | 3 ++-
> include/hw/virtio/virtio-iommu.h | 2 +-
> include/sysemu/cryptodev.h| 2 +-
> include/tcg/tcg.h | 2 +-
> pc-bios/s390-ccw/bootmap.h| 2 +-
> pc-bios/s390-ccw/sclp.h | 2 +-
> tests/qtest/libqos/ahci.h | 2 +-
> block/linux-aio.c | 2 +-
> hw/acpi/nvdimm.c | 6 +++---
> hw/dma/soc_dma.c | 2 +-
> hw/i386/x86.c | 2 +-
> hw/misc/omap_l4.c | 2 +-
> hw/nvram/eeprom93xx.c | 2 +-
> hw/rdma/vmw/pvrdma_qp_ops.c | 4 ++--
> hw/usb/dev-network.c | 2 +-
> hw/usb/dev-smartcard-reader.c | 4 ++--
> hw/virtio/virtio.c| 4 ++--
> net/queue.c | 2 +-
> 25 files changed, 38 insertions(+), 37 deletions(-)
>
> diff --git a/bsd-user/qemu.h b/bsd-user/qemu.h
> index 09e8aed9c7..f8bb1e5459 100644
> --- a/bsd-user/qemu.h
> +++ b/bsd-user/qemu.h
> @@ -95,7 +95,7 @@ typedef struct TaskState {
> struct sigqueue *first_free; /* first free siginfo queue entry */
> int signal_pending; /* non zero if a signal may be pending */
>
> -uint8_t stack[0];
> +uint8_t stack[];
> } __attribute__((aligned(16))) TaskState;
>
> void init_task_state(TaskState *ts);
> diff --git a/contrib/libvhost-user/libvhost-user.h
> b/contrib/libvhost-user/libvhost-user.h
> index 6fc8000e99..f30394fab6 100644
> --- a/contrib/libvhost-user/libvhost-user.h
> +++ b/contrib/libvhost-user/libvhost-user.h
> @@ -286,7 +286,7 @@ typedef struct VuVirtqInflight {
> uint16_t used_idx;
>
> /* Used to track the state of each descriptor in descriptor table */
> -VuDescStateSplit desc[0];
> +VuDescStateSplit desc[];
> } VuVirtqInflight;
>
> typedef struct VuVirtqInflightDesc {
> diff --git a/hw/m68k/bootinfo.h b/hw/m68k/bootinfo.h
> index 5f8ded2686..c954270aad 100644
> --- a/hw/m68k/bootinfo.h
> +++ b/hw/m68k/bootinfo.h
> @@ -14,7 +14,7 @@
> struct bi_record {
> uint16_t tag;/* tag ID */
> uint16_t size; /* size of record */
> -uint32_t data[0];/* data */
> +uint32_t data[]; /* data */
> };
>
> /* machine independent tags */
> diff --git a/hw/scsi/srp.h b/hw/scsi/srp.h
> index d27f31d2d5..54c954badd 100644
> --- a/hw/scsi/srp.h
> +++ b/hw/scsi/srp.h
> @@ -112,7 +112,7 @@ struct srp_direct_buf {
> struct srp_indirect_buf {
> struct srp_direct_buftable_desc;
> uint32_t
[Xen-devel] [PATCH v2 1/2] misc: Replace zero-length arrays with flexible array member (automatic)
Description copied from Linux kernel commit from Gustavo A. R. Silva
(see [3]):
--v-- description start --v--
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to
declare variable-length types such as these ones is a flexible
array member [1], introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler
warning in case the flexible array does not occur last in the
structure, which will help us prevent some kind of undefined
behavior bugs from being unadvertenly introduced [2] to the
Linux codebase from now on.
--^-- description end --^--
Do the similar housekeeping in the QEMU codebase (which uses
C99 since commit 7be41675f7cb).
All these instances of code were found with the help of the
following Coccinelle script:
@@
identifier s, m, a;
type t, T;
@@
struct s {
...
t m;
- T a[0];
+ T a[];
};
@@
identifier s, m, a;
type t, T;
@@
struct s {
...
t m;
- T a[0];
+ T a[];
} QEMU_PACKED;
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=76497732932f
[3]
https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/commit/?id=17642a2fbd2c1
Inspired-by: Gustavo A. R. Silva
Reviewed-by: David Hildenbrand
Signed-off-by: Philippe Mathieu-Daudé
---
v2: cocci script updated to not match structures of onlyi
a single flexible array member:
block/qed.h:106:14: error: flexible array member 'offsets' not allowed in
otherwise empty struct
uint64_t offsets[]; /* in bytes */
^
---
bsd-user/qemu.h | 2 +-
contrib/libvhost-user/libvhost-user.h | 2 +-
hw/m68k/bootinfo.h| 2 +-
hw/scsi/srp.h | 6 +++---
hw/xen/xen_pt.h | 2 +-
include/hw/acpi/acpi-defs.h | 12 ++--
include/hw/arm/smmu-common.h | 2 +-
include/hw/i386/intel_iommu.h | 3 ++-
include/hw/virtio/virtio-iommu.h | 2 +-
include/sysemu/cryptodev.h| 2 +-
include/tcg/tcg.h | 2 +-
pc-bios/s390-ccw/bootmap.h| 2 +-
pc-bios/s390-ccw/sclp.h | 2 +-
tests/qtest/libqos/ahci.h | 2 +-
block/linux-aio.c | 2 +-
hw/acpi/nvdimm.c | 6 +++---
hw/dma/soc_dma.c | 2 +-
hw/i386/x86.c | 2 +-
hw/misc/omap_l4.c | 2 +-
hw/nvram/eeprom93xx.c | 2 +-
hw/rdma/vmw/pvrdma_qp_ops.c | 4 ++--
hw/usb/dev-network.c | 2 +-
hw/usb/dev-smartcard-reader.c | 4 ++--
hw/virtio/virtio.c| 4 ++--
net/queue.c | 2 +-
25 files changed, 38 insertions(+), 37 deletions(-)
diff --git a/bsd-user/qemu.h b/bsd-user/qemu.h
index 09e8aed9c7..f8bb1e5459 100644
--- a/bsd-user/qemu.h
+++ b/bsd-user/qemu.h
@@ -95,7 +95,7 @@ typedef struct TaskState {
struct sigqueue *first_free; /* first free siginfo queue entry */
int signal_pending; /* non zero if a signal may be pending */
-uint8_t stack[0];
+uint8_t stack[];
} __attribute__((aligned(16))) TaskState;
void init_task_state(TaskState *ts);
diff --git a/contrib/libvhost-user/libvhost-user.h
b/contrib/libvhost-user/libvhost-user.h
index 6fc8000e99..f30394fab6 100644
--- a/contrib/libvhost-user/libvhost-user.h
+++ b/contrib/libvhost-user/libvhost-user.h
@@ -286,7 +286,7 @@ typedef struct VuVirtqInflight {
uint16_t used_idx;
/* Used to track the state of each descriptor in descriptor table */
-VuDescStateSplit desc[0];
+VuDescStateSplit desc[];
} VuVirtqInflight;
typedef struct VuVirtqInflightDesc {
diff --git a/hw/m68k/bootinfo.h b/hw/m68k/bootinfo.h
index 5f8ded2686..c954270aad 100644
--- a/hw/m68k/bootinfo.h
+++ b/hw/m68k/bootinfo.h
@@ -14,7 +14,7 @@
struct bi_record {
uint16_t tag;/* tag ID */
uint16_t size; /* size of record */
-uint32_t data[0];/* data */
+uint32_t data[]; /* data */
};
/* machine independent tags */
diff --git a/hw/scsi/srp.h b/hw/scsi/srp.h
index d27f31d2d5..54c954badd 100644
--- a/hw/scsi/srp.h
+++ b/hw/scsi/srp.h
@@ -112,7 +112,7 @@ struct srp_direct_buf {
struct srp_indirect_buf {
struct srp_direct_buftable_desc;
uint32_t len;
-struct srp_direct_bufdesc_list[0];
+struct srp_direct_bufdesc_list[];
} QEMU_PACKED;
enum {
@@ -211,7 +211,7 @@ struct srp_cmd {
uint8_treserved4;
uint8_tadd_cdb_len;
uint8_tcdb[16];
-uint8_tadd_data[0];
+uint8_tadd_data[];
} QEMU_PACKED;
enum {
@@ -241,7 +241,7 @@ struct srp_rsp {
uint32_t data_in_res_cnt;
uint32_t s
