From: DJ Delorie <dj@delorie.com>
To: cwilson@ece.gatech.edu
Cc: binutils@sources.redhat.com, cygwin@cygwin.com
Subject: Re: [aida_s@mx12.freecom.ne.jp: A serious bug of "ld --enable-auto-import"]
Date: Sun, 26 Aug 2001 09:43:00 -0000 [thread overview]
Message-ID: <200108261643.MAA06855@envy.delorie.com> (raw)
In-Reply-To: <3B891E23.9090407@ece.gatech.edu>
> Well, that's interesting. Since arrays ARE pointers(*), then perhaps
> it's enough to change gcc's behavior from
Not from gcc's perspective. From C's perspective, array symbols and
pointer symbols are mostly interchangeable, but they are not the same.
For example, these two declarations:
extern char *foo;
extern char foo[];
are *not* the same, and using the wrong one results in a broken
program.
For our purposes, a pointer is a symbol referencing a four-byte range
of memory that holds the address of a range of memory that holds a
sequence of characters, and an array is a symbol referencing a range
of memory that holds a sequence of characters. Because a pointer
requires an extra indirection, gcc is limited in the optimizations it
can do on it, but dealing with imports becomes simpler because the
address occurs in exactly one place.
Since a symbol is always a constant (regardless of what it refers to),
offsetting it by a constant results in a sum that can always be
computed at compile time (well, link time) and gcc will always do it
that way. This is a fairly fundamental concept in gcc, and I doubt it
would be practical to tell gcc to do it otherwise.
next prev parent reply other threads:[~2001-08-26 9:43 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-08-25 22:11 Charles S. Wilson
2001-08-25 22:30 ` DJ Delorie
2001-08-25 22:47 ` Charles Wilson
2001-08-25 23:14 ` DJ Delorie
2001-08-26 8:10 ` Charles Wilson
2001-08-26 8:43 ` DJ Delorie
2001-08-26 9:04 ` Charles Wilson
2001-08-26 9:43 ` DJ Delorie [this message]
2001-08-26 15:35 ` Charles Wilson
2001-08-26 12:27 ` Kurt Roeckx
-- strict thread matches above, loose matches on Subject: below --
2001-08-25 10:50 Christopher Faylor
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=200108261643.MAA06855@envy.delorie.com \
--to=dj@delorie.com \
--cc=binutils@sources.redhat.com \
--cc=cwilson@ece.gatech.edu \
--cc=cygwin@cygwin.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).