| Message ID | 20200304153816.23636-3-philmd@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | misc: Replace zero-length arrays with flexible array member | expand |
On Wed, Mar 04, 2020 at 04:38:16PM +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 command (then manual analysis, without modifying > structures only having a single flexible array member, such > QEDTable in block/qed.h): > > git grep -F '[0];' > > [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 <gustavo@embeddedor.com> > Reviewed-by: David Hildenbrand <david@redhat.com> > Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> > --- > v2: Do not modify block/qed.h: > > block/qed.h:106:14: error: flexible array member 'offsets' not allowed in otherwise empty struct > uint64_t offsets[]; /* in bytes */ > ^ > --- > docs/interop/vhost-user.rst | 4 ++-- > include/hw/acpi/acpi-defs.h | 4 ++-- > include/hw/boards.h | 2 +- > include/hw/s390x/event-facility.h | 2 +- > include/hw/s390x/sclp.h | 8 ++++---- > block/vmdk.c | 2 +- > hw/char/sclpconsole-lm.c | 2 +- > hw/char/sclpconsole.c | 2 +- > hw/s390x/virtio-ccw.c | 2 +- > target/s390x/ioinst.c | 2 +- > 10 files changed, 15 insertions(+), 15 deletions(-) > > diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst > index 401652397c..3b1b6602c7 100644 > --- a/docs/interop/vhost-user.rst > +++ b/docs/interop/vhost-user.rst > @@ -568,7 +568,7 @@ For split virtqueue, queue region can be implemented as: > uint16_t used_idx; > > /* Used to track the state of each descriptor in descriptor table */ > - DescStateSplit desc[0]; > + DescStateSplit desc[]; > } QueueRegionSplit; > > To track inflight I/O, the queue region should be processed as follows: > @@ -690,7 +690,7 @@ For packed virtqueue, queue region can be implemented as: > uint8_t padding[7]; > > /* Used to track the state of each descriptor fetched from descriptor ring */ > - DescStatePacked desc[0]; > + DescStatePacked desc[]; > } QueueRegionPacked; > > To track inflight I/O, the queue region should be processed as follows: > diff --git a/include/hw/acpi/acpi-defs.h b/include/hw/acpi/acpi-defs.h > index 19f7ba7b70..c13327fa78 100644 > --- a/include/hw/acpi/acpi-defs.h > +++ b/include/hw/acpi/acpi-defs.h > @@ -152,7 +152,7 @@ typedef struct AcpiSerialPortConsoleRedirection > */ > struct AcpiRsdtDescriptorRev1 { > ACPI_TABLE_HEADER_DEF /* ACPI common table header */ > - uint32_t table_offset_entry[0]; /* Array of pointers to other */ > + uint32_t table_offset_entry[]; /* Array of pointers to other */ > /* ACPI tables */ > } QEMU_PACKED; > typedef struct AcpiRsdtDescriptorRev1 AcpiRsdtDescriptorRev1; > @@ -162,7 +162,7 @@ typedef struct AcpiRsdtDescriptorRev1 AcpiRsdtDescriptorRev1; > */ > struct AcpiXsdtDescriptorRev2 { > ACPI_TABLE_HEADER_DEF /* ACPI common table header */ > - uint64_t table_offset_entry[0]; /* Array of pointers to other */ > + uint64_t table_offset_entry[]; /* Array of pointers to other */ > /* ACPI tables */ > } QEMU_PACKED; > typedef struct AcpiXsdtDescriptorRev2 AcpiXsdtDescriptorRev2; > diff --git a/include/hw/boards.h b/include/hw/boards.h > index 9bc42dfb22..c96120d15f 100644 > --- a/include/hw/boards.h > +++ b/include/hw/boards.h > @@ -71,7 +71,7 @@ typedef struct CPUArchId { > */ > typedef struct { > int len; > - CPUArchId cpus[0]; > + CPUArchId cpus[]; > } CPUArchIdList; > > /** > diff --git a/include/hw/s390x/event-facility.h b/include/hw/s390x/event-facility.h > index bdc32a3c09..700a610f33 100644 > --- a/include/hw/s390x/event-facility.h > +++ b/include/hw/s390x/event-facility.h > @@ -122,7 +122,7 @@ typedef struct MDBO { > > typedef struct MDB { > MdbHeader header; > - MDBO mdbo[0]; > + MDBO mdbo[]; > } QEMU_PACKED MDB; > > typedef struct SclpMsg { > diff --git a/include/hw/s390x/sclp.h b/include/hw/s390x/sclp.h > index c54413b78c..cd7b24359f 100644 > --- a/include/hw/s390x/sclp.h > +++ b/include/hw/s390x/sclp.h > @@ -132,7 +132,7 @@ typedef struct ReadInfo { > uint16_t highest_cpu; > uint8_t _reserved5[124 - 122]; /* 122-123 */ > uint32_t hmfai; > - struct CPUEntry entries[0]; > + struct CPUEntry entries[]; > } QEMU_PACKED ReadInfo; > > typedef struct ReadCpuInfo { > @@ -142,7 +142,7 @@ typedef struct ReadCpuInfo { > uint16_t nr_standby; /* 12-13 */ > uint16_t offset_standby; /* 14-15 */ > uint8_t reserved0[24-16]; /* 16-23 */ > - struct CPUEntry entries[0]; > + struct CPUEntry entries[]; > } QEMU_PACKED ReadCpuInfo; > > typedef struct ReadStorageElementInfo { > @@ -151,7 +151,7 @@ typedef struct ReadStorageElementInfo { > uint16_t assigned; > uint16_t standby; > uint8_t _reserved0[16 - 14]; /* 14-15 */ > - uint32_t entries[0]; > + uint32_t entries[]; > } QEMU_PACKED ReadStorageElementInfo; > > typedef struct AttachStorageElement { > @@ -159,7 +159,7 @@ typedef struct AttachStorageElement { > uint8_t _reserved0[10 - 8]; /* 8-9 */ > uint16_t assigned; > uint8_t _reserved1[16 - 12]; /* 12-15 */ > - uint32_t entries[0]; > + uint32_t entries[]; > } QEMU_PACKED AttachStorageElement; > > typedef struct AssignStorage { > diff --git a/block/vmdk.c b/block/vmdk.c > index 20e909d997..8466051bc9 100644 > --- a/block/vmdk.c > +++ b/block/vmdk.c > @@ -187,7 +187,7 @@ typedef struct VmdkMetaData { > typedef struct VmdkGrainMarker { > uint64_t lba; > uint32_t size; > - uint8_t data[0]; > + uint8_t data[]; > } QEMU_PACKED VmdkGrainMarker; > > enum { > diff --git a/hw/char/sclpconsole-lm.c b/hw/char/sclpconsole-lm.c > index c420dc066e..2b5f37b6a2 100644 > --- a/hw/char/sclpconsole-lm.c > +++ b/hw/char/sclpconsole-lm.c > @@ -31,7 +31,7 @@ > typedef struct OprtnsCommand { > EventBufferHeader header; > MDMSU message_unit; > - char data[0]; > + char data[]; > } QEMU_PACKED OprtnsCommand; > > /* max size for line-mode data in 4K SCCB page */ > diff --git a/hw/char/sclpconsole.c b/hw/char/sclpconsole.c > index 1fa124dab9..5c7664905e 100644 > --- a/hw/char/sclpconsole.c > +++ b/hw/char/sclpconsole.c > @@ -25,7 +25,7 @@ > > typedef struct ASCIIConsoleData { > EventBufferHeader ebh; > - char data[0]; > + char data[]; > } QEMU_PACKED ASCIIConsoleData; > > /* max size for ASCII data in 4K SCCB page */ > diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c > index 50cf95b781..64f928fc7d 100644 > --- a/hw/s390x/virtio-ccw.c > +++ b/hw/s390x/virtio-ccw.c > @@ -193,7 +193,7 @@ typedef struct VirtioThinintInfo { > typedef struct VirtioRevInfo { > uint16_t revision; > uint16_t length; > - uint8_t data[0]; > + uint8_t data[]; > } QEMU_PACKED VirtioRevInfo; > > /* Specify where the virtqueues for the subchannel are in guest memory. */ > diff --git a/target/s390x/ioinst.c b/target/s390x/ioinst.c > index c437a1d8c6..0e840cc579 100644 > --- a/target/s390x/ioinst.c > +++ b/target/s390x/ioinst.c > @@ -347,7 +347,7 @@ typedef struct ChscResp { > uint16_t len; > uint16_t code; > uint32_t param; > - char data[0]; > + char data[]; > } QEMU_PACKED ChscResp; > > #define CHSC_MIN_RESP_LEN 0x0008 > -- > 2.21.1
diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst index 401652397c..3b1b6602c7 100644 --- a/docs/interop/vhost-user.rst +++ b/docs/interop/vhost-user.rst @@ -568,7 +568,7 @@ For split virtqueue, queue region can be implemented as: uint16_t used_idx; /* Used to track the state of each descriptor in descriptor table */ - DescStateSplit desc[0]; + DescStateSplit desc[]; } QueueRegionSplit; To track inflight I/O, the queue region should be processed as follows: @@ -690,7 +690,7 @@ For packed virtqueue, queue region can be implemented as: uint8_t padding[7]; /* Used to track the state of each descriptor fetched from descriptor ring */ - DescStatePacked desc[0]; + DescStatePacked desc[]; } QueueRegionPacked; To track inflight I/O, the queue region should be processed as follows: diff --git a/include/hw/acpi/acpi-defs.h b/include/hw/acpi/acpi-defs.h index 19f7ba7b70..c13327fa78 100644 --- a/include/hw/acpi/acpi-defs.h +++ b/include/hw/acpi/acpi-defs.h @@ -152,7 +152,7 @@ typedef struct AcpiSerialPortConsoleRedirection */ struct AcpiRsdtDescriptorRev1 { ACPI_TABLE_HEADER_DEF /* ACPI common table header */ - uint32_t table_offset_entry[0]; /* Array of pointers to other */ + uint32_t table_offset_entry[]; /* Array of pointers to other */ /* ACPI tables */ } QEMU_PACKED; typedef struct AcpiRsdtDescriptorRev1 AcpiRsdtDescriptorRev1; @@ -162,7 +162,7 @@ typedef struct AcpiRsdtDescriptorRev1 AcpiRsdtDescriptorRev1; */ struct AcpiXsdtDescriptorRev2 { ACPI_TABLE_HEADER_DEF /* ACPI common table header */ - uint64_t table_offset_entry[0]; /* Array of pointers to other */ + uint64_t table_offset_entry[]; /* Array of pointers to other */ /* ACPI tables */ } QEMU_PACKED; typedef struct AcpiXsdtDescriptorRev2 AcpiXsdtDescriptorRev2; diff --git a/include/hw/boards.h b/include/hw/boards.h index 9bc42dfb22..c96120d15f 100644 --- a/include/hw/boards.h +++ b/include/hw/boards.h @@ -71,7 +71,7 @@ typedef struct CPUArchId { */ typedef struct { int len; - CPUArchId cpus[0]; + CPUArchId cpus[]; } CPUArchIdList; /** diff --git a/include/hw/s390x/event-facility.h b/include/hw/s390x/event-facility.h index bdc32a3c09..700a610f33 100644 --- a/include/hw/s390x/event-facility.h +++ b/include/hw/s390x/event-facility.h @@ -122,7 +122,7 @@ typedef struct MDBO { typedef struct MDB { MdbHeader header; - MDBO mdbo[0]; + MDBO mdbo[]; } QEMU_PACKED MDB; typedef struct SclpMsg { diff --git a/include/hw/s390x/sclp.h b/include/hw/s390x/sclp.h index c54413b78c..cd7b24359f 100644 --- a/include/hw/s390x/sclp.h +++ b/include/hw/s390x/sclp.h @@ -132,7 +132,7 @@ typedef struct ReadInfo { uint16_t highest_cpu; uint8_t _reserved5[124 - 122]; /* 122-123 */ uint32_t hmfai; - struct CPUEntry entries[0]; + struct CPUEntry entries[]; } QEMU_PACKED ReadInfo; typedef struct ReadCpuInfo { @@ -142,7 +142,7 @@ typedef struct ReadCpuInfo { uint16_t nr_standby; /* 12-13 */ uint16_t offset_standby; /* 14-15 */ uint8_t reserved0[24-16]; /* 16-23 */ - struct CPUEntry entries[0]; + struct CPUEntry entries[]; } QEMU_PACKED ReadCpuInfo; typedef struct ReadStorageElementInfo { @@ -151,7 +151,7 @@ typedef struct ReadStorageElementInfo { uint16_t assigned; uint16_t standby; uint8_t _reserved0[16 - 14]; /* 14-15 */ - uint32_t entries[0]; + uint32_t entries[]; } QEMU_PACKED ReadStorageElementInfo; typedef struct AttachStorageElement { @@ -159,7 +159,7 @@ typedef struct AttachStorageElement { uint8_t _reserved0[10 - 8]; /* 8-9 */ uint16_t assigned; uint8_t _reserved1[16 - 12]; /* 12-15 */ - uint32_t entries[0]; + uint32_t entries[]; } QEMU_PACKED AttachStorageElement; typedef struct AssignStorage { diff --git a/block/vmdk.c b/block/vmdk.c index 20e909d997..8466051bc9 100644 --- a/block/vmdk.c +++ b/block/vmdk.c @@ -187,7 +187,7 @@ typedef struct VmdkMetaData { typedef struct VmdkGrainMarker { uint64_t lba; uint32_t size; - uint8_t data[0]; + uint8_t data[]; } QEMU_PACKED VmdkGrainMarker; enum { diff --git a/hw/char/sclpconsole-lm.c b/hw/char/sclpconsole-lm.c index c420dc066e..2b5f37b6a2 100644 --- a/hw/char/sclpconsole-lm.c +++ b/hw/char/sclpconsole-lm.c @@ -31,7 +31,7 @@ typedef struct OprtnsCommand { EventBufferHeader header; MDMSU message_unit; - char data[0]; + char data[]; } QEMU_PACKED OprtnsCommand; /* max size for line-mode data in 4K SCCB page */ diff --git a/hw/char/sclpconsole.c b/hw/char/sclpconsole.c index 1fa124dab9..5c7664905e 100644 --- a/hw/char/sclpconsole.c +++ b/hw/char/sclpconsole.c @@ -25,7 +25,7 @@ typedef struct ASCIIConsoleData { EventBufferHeader ebh; - char data[0]; + char data[]; } QEMU_PACKED ASCIIConsoleData; /* max size for ASCII data in 4K SCCB page */ diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c index 50cf95b781..64f928fc7d 100644 --- a/hw/s390x/virtio-ccw.c +++ b/hw/s390x/virtio-ccw.c @@ -193,7 +193,7 @@ typedef struct VirtioThinintInfo { typedef struct VirtioRevInfo { uint16_t revision; uint16_t length; - uint8_t data[0]; + uint8_t data[]; } QEMU_PACKED VirtioRevInfo; /* Specify where the virtqueues for the subchannel are in guest memory. */ diff --git a/target/s390x/ioinst.c b/target/s390x/ioinst.c index c437a1d8c6..0e840cc579 100644 --- a/target/s390x/ioinst.c +++ b/target/s390x/ioinst.c @@ -347,7 +347,7 @@ typedef struct ChscResp { uint16_t len; uint16_t code; uint32_t param; - char data[0]; + char data[]; } QEMU_PACKED ChscResp; #define CHSC_MIN_RESP_LEN 0x0008
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 command (then manual analysis, without modifying structures only having a single flexible array member, such QEDTable in block/qed.h): git grep -F '[0];' [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 <gustavo@embeddedor.com> Reviewed-by: David Hildenbrand <david@redhat.com> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com> --- v2: Do not modify block/qed.h: block/qed.h:106:14: error: flexible array member 'offsets' not allowed in otherwise empty struct uint64_t offsets[]; /* in bytes */ ^ --- docs/interop/vhost-user.rst | 4 ++-- include/hw/acpi/acpi-defs.h | 4 ++-- include/hw/boards.h | 2 +- include/hw/s390x/event-facility.h | 2 +- include/hw/s390x/sclp.h | 8 ++++---- block/vmdk.c | 2 +- hw/char/sclpconsole-lm.c | 2 +- hw/char/sclpconsole.c | 2 +- hw/s390x/virtio-ccw.c | 2 +- target/s390x/ioinst.c | 2 +- 10 files changed, 15 insertions(+), 15 deletions(-)