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Re: Correct logic for "defined by object"
- From: Alan Modra <amodra at gmail dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: Binutils <binutils at sourceware dot org>
- Date: Wed, 24 Dec 2014 00:05:57 +1030
- Subject: Re: Correct logic for "defined by object"
- Authentication-results: sourceware.org; auth=none
- References: <20141223124131 dot GB4313 at bubble dot grove dot modra dot org> <CAMe9rOr_z64ZWtbSOwF_GT_-p5Sn-QE4KKKg0s6MVPFU3jPLEA at mail dot gmail dot com> <20141223130605 dot GF4313 at bubble dot grove dot modra dot org> <CAMe9rOoSVkK4vL4swPcwm_Fy=yr6r4Ss8HVFk0Xy267AcQ=79A at mail dot gmail dot com>
On Tue, Dec 23, 2014 at 05:10:13AM -0800, H.J. Lu wrote:
> On Tue, Dec 23, 2014 at 5:06 AM, Alan Modra <firstname.lastname@example.org> wrote:
> > On Tue, Dec 23, 2014 at 04:46:29AM -0800, H.J. Lu wrote:
> >> No testcase?
> > No. This patch wasn't in response to a bug report or from observing
> > wrong linker behaviour myself. In fact, I don't think you can write a
> > testcase that fails with the old code and passes with the new, due to
> > the way def->by_object is used. The patch was really just a tidy.
> So this patch won't change linker behavior in any way whatsoever.
I didn't go looking for possible failure modes in the old code. On
thinking about it some more, it may have been possible to induce wrong
behaviour with objects that had an undefined weak "x" and a script
with DEFINED(x) in an expression preceding an assignment to "x".
> Basically the setting of def->by_object is unused.
No, it is used in fold_name, case DEFINED:
new_number (h != NULL
&& (h->type == bfd_link_hash_defined
|| h->type == bfd_link_hash_defweak
|| h->type == bfd_link_hash_common)
&& ((def = symbol_defined (tree->name.name)) == NULL
|| def->iteration == (lang_statement_iteration & 1)));
Australia Development Lab, IBM