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From: Peter Maydell <peter.maydell@linaro.org>
Date: Fri, 10 Jul 2015 14:38:36 +0100
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Subject: Re: [Qemu-devel] [PATCH] crypt: fix build with nettle >= 3.0.0
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To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>
Cc: QEMU Developers <qemu-devel@nongnu.org>

On 10 July 2015 at 14:31, Radim Kr=C4=8Dm=C3=A1=C5=99 <rkrcmar@redhat.com> =
wrote:
> 2015-07-10 13:56+0100, Peter Maydell:
>> On 10 July 2015 at 13:33, Radim Kr=C4=8Dm=C3=A1=C5=99 <rkrcmar@redhat.co=
m> wrote:
>>> @@ -83,8 +87,8 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgori=
thm alg,
>>> -        ctx->alg_encrypt =3D (nettle_crypt_func *)des_encrypt;
>>> -        ctx->alg_decrypt =3D (nettle_crypt_func *)des_decrypt;
>>> +        ctx->alg_encrypt =3D (nettle_cipher_func *)des_encrypt;
>>> +        ctx->alg_decrypt =3D (nettle_cipher_func *)des_decrypt;
>>> @@ -98,8 +102,8 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgor=
ithm alg,
>>> -        ctx->alg_encrypt =3D (nettle_crypt_func *)aes_encrypt;
>>> -        ctx->alg_decrypt =3D (nettle_crypt_func *)aes_decrypt;
>>> +        ctx->alg_encrypt =3D (nettle_cipher_func *)aes_encrypt;
>>> +        ctx->alg_decrypt =3D (nettle_cipher_func *)aes_decrypt;
>>
>> Why do we need the casts here at all?  If the functions
>> we're passing around don't have the right signature
>> anyway we're in big trouble and casting them is
>> just going to hide the problem until runtime...
>
> Yes.
>
> We pass 'ctx' as a 'void *' in the code, but these functions accept
> specialized structures, which makes them incompatible:
>
>   void nettle_cipher_func(const void *ctx, size_t length, [...])
>
>   void aes_decrypt(const struct aes_ctx *ctx, size_t length, [...])
>   void des_decrypt(const struct des_ctx *ctx, size_t length, [...])

But aren't both the typedef and the aes/des_decrypt functions
provided by the nettle library? Why is the library providing
functions whose prototypes don't match its own typedef?

-- PMM