Re: Update LTO plugin interface

[Ian Lance Taylor <iant at google dot com>]

"H.J. Lu" <hjl.tools@gmail.com> writes:

> On Thu, Dec 2, 2010 at 9:41 AM, Ian Lance Taylor <iant@google.com> wrote:
>> "H.J. Lu" <hjl.tools@gmail.com> writes:
>>
>>> How do you deal with -lm:
>>
>> I believe we have agreed that LTO can only introduce new symbol
>> references that are satisfied by -lc and -lgcc. ÂUnder those conditions,
>
> Have you looked my testcase? The assumption of "LTO can only
> introduce new symbol references that are satisfied by -lc and -lgcc."
> is wrong.  My testcase shows LTO may introduce new symbol references
> to libm.

You're right, I didn't fully grasp that the reference to sin in the
source code was somehow being removed and then re-added.

However, I really don't see why this is a serious flaw in my proposal.
You have shown a case in which LTO can introduce a new symbol reference
to -lm.  So we just treat -lm as we do -lc and -lgcc.  This is similar
to how the g++ driver already treats -lm.  It's a detail, not a major
problem.

A major problem would be if LTO could introduce a new symbol reference
which required changing the way we search user defined archives.

Ian