Comment 19 for bug 1803872

On Tue, 18 Dec 2018 18:51:20 +0100
Philippe Mathieu-Daudé <email address hidden> wrote:

> GCC 8 added a -Wstringop-truncation warning:
>
> The -Wstringop-truncation warning added in GCC 8.0 via r254630 for
> bug 81117 is specifically intended to highlight likely unintended
> uses of the strncpy function that truncate the terminating NUL
> character from the source string.
>
> This new warning leads to compilation failures:
>
> CC hw/acpi/core.o
> In function 'acpi_table_install', inlined from 'acpi_table_add' at qemu/hw/acpi/core.c:296:5:
> qemu/hw/acpi/core.c:184:9: error: 'strncpy' specified bound 4 equals destination size [-Werror=stringop-truncation]
> strncpy(ext_hdr->sig, hdrs->sig, sizeof ext_hdr->sig);
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> make: *** [qemu/rules.mak:69: hw/acpi/core.o] Error 1
>
> Use the QEMU_NONSTRING attribute, since ACPI tables don't require the
> strings to be NUL-terminated.
>
> Suggested-by: Michael S. Tsirkin <email address hidden>
> Signed-off-by: Philippe Mathieu-Daudé <email address hidden>
> ---
> hw/acpi/core.c | 8 ++++----
> include/hw/acpi/acpi-defs.h | 8 ++++----
> 2 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/hw/acpi/core.c b/hw/acpi/core.c
> index aafdc61648..f60f750c3d 100644
> --- a/hw/acpi/core.c
> +++ b/hw/acpi/core.c
> @@ -35,14 +35,14 @@
> struct acpi_table_header {
> uint16_t _length; /* our length, not actual part of the hdr */
> /* allows easier parsing for fw_cfg clients */
> - char sig[4]; /* ACPI signature (4 ASCII characters) */
> + char sig[4] QEMU_NONSTRING; /* ACPI signature (4 ASCII characters) */
> uint32_t length; /* Length of table, in bytes, including header */
> uint8_t revision; /* ACPI Specification minor version # */
> uint8_t checksum; /* To make sum of entire table == 0 */
> - char oem_id[6]; /* OEM identification */
> - char oem_table_id[8]; /* OEM table identification */
> + char oem_id[6] QEMU_NONSTRING; /* OEM identification */
> + char oem_table_id[8] QEMU_NONSTRING; /* OEM table identification */
> uint32_t oem_revision; /* OEM revision number */
> - char asl_compiler_id[4]; /* ASL compiler vendor ID */
> + char asl_compiler_id[4] QEMU_NONSTRING; /* ASL compiler vendor ID */
> uint32_t asl_compiler_revision; /* ASL compiler revision number */
> } QEMU_PACKED;
>
> diff --git a/include/hw/acpi/acpi-defs.h b/include/hw/acpi/acpi-defs.h
> index af8e023968..3bf0bec8ba 100644
> --- a/include/hw/acpi/acpi-defs.h
> +++ b/include/hw/acpi/acpi-defs.h
> @@ -43,7 +43,7 @@ enum {
> struct AcpiRsdpDescriptor { /* Root System Descriptor Pointer */
> uint64_t signature; /* ACPI signature, contains "RSD PTR " */
> uint8_t checksum; /* To make sum of struct == 0 */
> - uint8_t oem_id [6]; /* OEM identification */
> + uint8_t oem_id [6] QEMU_NONSTRING; /* OEM identification */
> uint8_t revision; /* Must be 0 for 1.0, 2 for 2.0 */
> uint32_t rsdt_physical_address; /* 32-bit physical address of RSDT */
> uint32_t length; /* XSDT Length in bytes including hdr */

you'll need to rebase this on top the latest Michael's pull request.
[PULL v2 25/30] hw: arm: Carry RSDP specific data through AcpiRsdpData
[PULL v2 29/30] hw: acpi: Remove AcpiRsdpDescriptor and fix tests

> @@ -62,10 +62,10 @@ typedef struct AcpiRsdpDescriptor AcpiRsdpDescriptor;
> uint32_t length; /* Length of table, in bytes, including header */ \
> uint8_t revision; /* ACPI Specification minor version # */ \
> uint8_t checksum; /* To make sum of entire table == 0 */ \
> - uint8_t oem_id [6]; /* OEM identification */ \
> - uint8_t oem_table_id [8]; /* OEM table identification */ \
> + uint8_t oem_id [6] QEMU_NONSTRING; /* OEM identification */ \
> + uint8_t oem_table_id [8] QEMU_NONSTRING; /* OEM table identification */ \
> uint32_t oem_revision; /* OEM revision number */ \
> - uint8_t asl_compiler_id [4]; /* ASL compiler vendor ID */ \
> + uint8_t asl_compiler_id [4] QEMU_NONSTRING; /* ASL compiler vendor ID */ \
> uint32_t asl_compiler_revision; /* ASL compiler revision number */
>
>