From: Alexandre Oliva <oliva@dcc.unicamp.br>
To: Zack Weinberg <zack@rabi.columbia.edu>
Cc: egcs@egcs.cygnus.com
Subject: Re: making aliases into the middle of a structure
Date: Fri, 30 Apr 1999 23:15:00 -0000 [thread overview]
Message-ID: <org15s33hj.fsf@lua.lbi.dcc.unicamp.br> (raw)
Message-ID: <19990430231500.6cDr5f6oxOr3Ok3Jz9MSiVKPtpIWeoRaXfdlLtL1Qg4@z> (raw)
In-Reply-To: <199904221830.OAA07523@blastula.phys.columbia.edu>
On Apr 22, 1999, Zack Weinberg <zack@rabi.columbia.edu> wrote:
> On 22 Apr 1999 15:24:46 -0300, Alexandre Oliva wrote:
>> On Apr 22, 1999, Zack Weinberg <zack@rabi.columbia.edu> wrote:
>>
>>> extern __typeof(x.b) y __attribute__ ((alias("x.b")));
>>
>> This can't work. The alias attribute defines an alias to a *symbol*,
>> not to an arbitrary expression.
> I don't see that it would be terribly hard to extend alias so it could
> handle SYMBOL_REFs and COMPONENT_REFs as well as strings.
That would probably be a good idea. alias could accept an arbitrary
expression. If it's an lvalue within a global symbol, it will define
an actual alias, otherwise it could just emit an error or ``construct
a temporary and bind the reference to it'', to put it in C++ terms :-)
>> why don't you compute the offset, say, in the configure
>> script, then #define the appropriate alias string?
> Because the preprocessor can't compute offsetof() all the way down;
> I'd have to compile and run a test program. Which loses when
> cross-compiling.
Well, you could try to extract this information from the assembly
code, or from some RTL dump (since you're bound to gcc anyway), but I
wouldn't like to be the one to implement it :-)
--
Alexandre Oliva http://www.dcc.unicamp.br/~oliva IC-Unicamp, Brasil
{oliva,Alexandre.Oliva}@dcc.unicamp.br aoliva@{acm.org,computer.org}
oliva@{gnu.org,kaffe.org,{egcs,sourceware}.cygnus.com,samba.org}
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next prev parent reply other threads:[~1999-04-30 23:15 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-04-22 11:13 Zack Weinberg
1999-04-22 11:25 ` Alexandre Oliva
1999-04-22 11:30 ` Zack Weinberg
1999-04-22 11:38 ` Alexandre Oliva [this message]
1999-04-22 14:31 ` Zack Weinberg
1999-04-23 15:24 ` Richard Henderson
1999-04-23 16:27 ` Zack Weinberg
1999-04-23 16:52 ` Richard Henderson
1999-04-30 23:15 ` Richard Henderson
1999-04-30 23:15 ` Zack Weinberg
1999-04-30 23:15 ` Richard Henderson
1999-04-30 23:15 ` Zack Weinberg
1999-04-23 10:34 ` Jeffrey A Law
1999-04-23 10:40 ` Zack Weinberg
1999-04-23 15:54 ` Richard Henderson
1999-04-23 16:19 ` Zack Weinberg
1999-04-26 1:46 ` Andreas Schwab
1999-04-30 23:15 ` Andreas Schwab
1999-04-30 23:15 ` Zack Weinberg
1999-04-30 23:15 ` Richard Henderson
1999-04-30 23:15 ` Zack Weinberg
1999-04-23 13:36 ` Jamie Lokier
1999-04-23 13:49 ` Zack Weinberg
1999-04-23 15:20 ` Jamie Lokier
1999-04-30 23:15 ` Jamie Lokier
1999-04-23 22:58 ` Andi Kleen
1999-04-30 23:15 ` Andi Kleen
1999-04-30 23:15 ` Zack Weinberg
1999-04-24 21:53 ` Jeffrey A Law
1999-04-30 23:15 ` Jeffrey A Law
1999-04-30 23:15 ` Jamie Lokier
1999-04-30 23:15 ` Jeffrey A Law
1999-04-30 23:15 ` Alexandre Oliva
1999-04-30 23:15 ` Zack Weinberg
1999-04-30 23:15 ` Alexandre Oliva
1999-04-30 23:15 ` Zack Weinberg
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