Re: [U-Boot] [PATCH 2/3] md5: Fix gcc-4.7 build problem in md5

Dear Pavel,

In message 20121105200340.GA15821@xo-6d-61-c0.localdomain you wrote:

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/* Append length in bits and transform */

• ctx->in32[14] = ctx->bits[0];
• ctx->in32[15] = ctx->bits[1];

• memcpy(ctx->in + 14 * sizeof(__u32), ctx->bits, 2 * sizeof(__u32));

This makes the code actually unreadable. Please add at least a comment what this is doing.

Actually I think this shoul dbe split into two memcpy commands, using the addresses of the respective array elements directly, without such manual pointer arithmetics.

I guess bigger question is: why does gcc miscompile that, and is it guaranteed that it will not miscompile the memcpy?

I did not see Simon mentioning anythin about incorrect compilation. My understanding was that it's just the usual "dereferencing type-punned pointer" warnings issue.

Simon, what was the actual problem this was supposed to fix?

Best regards,

Wolfgang Denk