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Message-ID: <552F95C2.3080103@iki.fi>
Date: Thu, 16 Apr 2015 10:58:00 -0000
From: Jarkko Hietaniemi <jhi@iki.fi>
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To: libffi-discuss@sourceware.org
Subject: Re: src/alpha/ffitarget.h  - FFI_TRAMPOLINE_SIZE
References: <mgn9sa$lom$1@ger.gmane.org>
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On Wednesday-201504-15 23:20, John E. Malmberg wrote:
>     tramp = (unsigned int *) &closure->tramp[0];
>     ....
>
>      *(void **) &tramp[4] = ffi_closure_osf;
>
> But tramp only has 3 longword members per the previous declaration, so
> &tramp[4] is the address of the '*cif' member of the structure which is
> then updated:

unsigned int is four bytes in alpha.  (LP64, not ILP64).
So writing an 8-byte ptr at int offset 4 or byte offset 16
will update the bytes 16 to 23.  Verified in an alpha, and
for that matter in an x86_64, which is LP64, too.