On 5/13/19 12:45 PM, Frediano Ziglio wrote:
Do not declare the structure as aligned. The start/end-packed.h headers affects only MingW or Microsoft compilers.
They also define/undef SPICE_ATTR_PACKED which affects Linux. BTW, if we define PACKED as ALIGNED(1) does that work for Windows too (I mean instead of pragma pack) ?
To have unaligned structure with GCC compiler you have to use SPICE_ATTR_PACKED. This way the definition are the same for all compiler.
This structure is used in a lot of QXL structures which are not aligned causing to have an aligned structure to be potentially unaligned. As this structure has no holes this change does not make any size change using any compiler.
For this reason, this change looks safe to me.
The change will only change the alignment from 4/8 to 1. This could affect structures containing this union however beside packed structure in qxl_dev.h (which are not affected) there are no other usages as such by spice-gtk, Qemu or spice-server.
It is used in Qemu, in hw/display/qxl.h, struct PCIQXLDevice. Also it's used in spice-server and likely QXL drivers too. Uri.
Signed-off-by: Frediano Ziglio <fziglio@xxxxxxxxxx> --- spice/qxl_dev.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/spice/qxl_dev.h b/spice/qxl_dev.h index a9cc4f4..659f930 100644 --- a/spice/qxl_dev.h +++ b/spice/qxl_dev.h @@ -275,7 +275,7 @@ typedef struct SPICE_ATTR_ALIGNED(4) SPICE_ATTR_PACKED QXLRam {} QXLRam; -typedef union QXLReleaseInfo {+typedef union SPICE_ATTR_PACKED QXLReleaseInfo { uint64_t id; // in uint64_t next; // out } QXLReleaseInfo;
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