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Date: Wed, 18 Jul 2012 18:15:39 +0100
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From: Peter Maydell <peter.maydell@linaro.org>
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Subject: Re: [Qemu-devel] qemu in full emulation on win32
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To: Stefan Weil <sw@weilnetz.de>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>, qemu-devel@nongnu.org, Hannes Reinecke <hare@suse.de>, Paolo Bonzini <pbonzini@redhat.com>, David Gibson <david@gibson.dropbear.id.au>, Richard Henderson <rth@twiddle.net>

On 18 July 2012 17:29, Stefan Weil <sw@weilnetz.de> wrote:
> Am 18.07.2012 10:01, schrieb Peter Maydell:
>> I think this struct should use QEMU_PACKED, which will
>> ensure that it is packed to GCC rules rather than MS
>> rules.
>>
>> We also seem to have let a pile of new uses of attribute((packed))
>> slip in in hw/mfi.h. Those are probably bugs too.

> They are bugs (for w32 / w64 hosts). I just sent a patch to fix them.
>
> Some more which I did not fix are in the TCG debugger interface.
> Maybe those also need to be fixed for w32 / w64, but that needs
> more tests and reading of the debugger interface documentation.
> Maybe Richard Henderson knows whether they should use QEMU_PACKED,
> too.

So, I think none of these structs will get actually used on
Windows, because they're ELF structure layouts which only
get used on hosts with ELF support. However I think it would
be nice to use QEMU_PACKED for consistency.

We can clearly straightforwardly switch the DebugInfo struct
in tcg/tcg.c to use QEMU_PACKED.

The remaining cases are all the same, in tcg/*/tcg-target.c:

typedef struct {
    uint32_t len __attribute__((aligned((sizeof(void *)))));
    uint32_t cie_offset;
    tcg_target_long func_start __attribute__((packed));
    tcg_target_long func_len __attribute__((packed));
    uint8_t def_cfa[4];
    uint8_t reg_ofs[14];
} DebugFrameFDE;

I think we can just remove the packed attributes from the
struct member fields and apply QEMU_PACKED to the whole struct:
I don't think this will change any of the alignment or packing
in the not-windows case.

(It's not clear to me why the alignment attribute is applied
to the len field rather than to the whole struct, but we
don't need to change that I guess.)

-- PMM