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From: Amittai Aviram <amittai.aviram@yale.edu>
To: Jonathan Wakely <jwakely.gcc@gmail.com>
Cc: gcc-help@gcc.gnu.org
Subject: Re: GCC Internals: built-in functions?
Date: Mon, 31 Jan 2011 04:53:00 -0000	[thread overview]
Message-ID: <D9ECD18C-E07F-4F71-A9B8-CB50A129635A@yale.edu> (raw)
In-Reply-To: <AANLkTi=SW=1jH8sk_1zLVbNGPHo4CoNRS27D3+WkCNjj@mail.gmail.com>

On Jan 30, 2011, at 4:07 PM, Jonathan Wakely wrote:

> On 30 January 2011 21:02, Amittai Aviram wrote:
>> 
>> I tried it with strncpy and with __builtin_strncpy, with exactly the same results, i.e., the assembly code still calls strncpy with three arguments.
> 
> Did you enable optimization?

I hadn't and that did it--even with just "-O1."  Thank you!  Very interesting!—

        movl    $1280066888, (%rsp)
        movw    $79, 4(%rsp)

The first integer in hex is 4C 4C 45 48 ( == 'L','L','E','H')
and the second (79) is 4F ( == 'O')

So, of course, it works out when assigned in little-endian order.   The second assignment also puts NULL in the right place as the higher-order bits of the integer 79.

Amittai Aviram
PhD Student in Computer Science
Yale University
646 483 2639
amittai.aviram@yale.edu
http://www.amittai.com

      reply	other threads:[~2011-01-30 21:28 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-30 20:50 Amittai Aviram
2011-01-30 21:01 ` Jonathan Wakely
2011-01-30 21:07   ` Amittai Aviram
2011-01-30 21:28     ` Jonathan Wakely
2011-01-31  4:53       ` Amittai Aviram [this message]

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