From: Tracy Kuhrt <Tracy.Kuhrt@microchip.com>
To: Ian Lance Taylor <ian@zembu.com>
Cc: binutils@sourceware.cygnus.com
Subject: Re: fx_offset Population
Date: Thu, 30 Aug 2001 13:41:00 -0000 [thread overview]
Message-ID: <3B8EA523.A8C81523@microchip.com> (raw)
In-Reply-To: <si4rqpwbtj.fsf@daffy.airs.com>
Ian,
Here is some more detail...
The new target that I am porting is using a COFF format. I am trying to
place the addend value in the 16-bits that I have for this operand. Where
the problem comes in is after fixup_segment calls the md_apply_fix3 function
(which divides this addend by 2) it then checks to see that the value it will
be writing is able to fit into 2 bytes. 2147450880 (0x7FFF8000) does not fit
and I get the error "Value of 2147450880 too large for field of 2 bytes at
0". But a -32768 should fit in 2 bytes.
Does this mean that anywhere that my md_apply_fix3 function uses the
fx_offset field in a calculation it must first convert it back to a signed
value?
Let me know if I can provide some more detail.
Tracy
Ian Lance Taylor wrote:
> Tracy Kuhrt <Tracy.Kuhrt@microchip.com> writes:
>
> > In fix_new_internal, the fx_offset member of the fixP structure is
> > populated with the offset, which is the value from the expressionS
> > structure's'X_add_number. The problem...
> >
> > X_add_number is an offsetT (which in the end is a signed value).
> > fx_offset is a valueT (which in the end is an unsigned value).
> > When setting fx_offset to X_add_number, X_add_number is converted from a
> > signed value to an unsigned value. So in my test case, I have the
> > expression . - 65536. When the fixup is created -65536 is converted to
> > an unsigned 4294901760.
> >
> > What would be the harm of changing fx_offset to be an offsetT?
>
> Probably none.
>
> However, at the level of the assembler, the differences between signed
> and unsigned numbers in relocation offsets are, as far as I know,
> inconsequential. I understand what you write above, but I don't
> understand what the actual problem is. Even if you change fx_offset,
> the number is just going to wind up in the addend field of an arelent,
> and that is also unsigned.
>
> Can you explain the real problem?
>
> Ian
next prev parent reply other threads:[~2001-08-30 13:41 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-08-30 13:03 Tracy Kuhrt
2001-08-30 13:08 ` Ian Lance Taylor
2001-08-30 13:41 ` Tracy Kuhrt [this message]
2001-08-30 13:59 ` Ian Lance Taylor
2001-08-30 14:11 ` Tracy Kuhrt
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=3B8EA523.A8C81523@microchip.com \
--to=tracy.kuhrt@microchip.com \
--cc=binutils@sourceware.cygnus.com \
--cc=ian@zembu.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).