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Re: [PATCH] Enable hidden visibility in libc.a compiled with PIE
- From: Szabolcs Nagy <szabolcs dot nagy at arm dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: nd at arm dot com, GNU C Library <libc-alpha at sourceware dot org>
- Date: Mon, 21 Aug 2017 17:50:05 +0100
- Subject: Re: [PATCH] Enable hidden visibility in libc.a compiled with PIE
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On 21/08/17 17:44, H.J. Lu wrote:
> On Mon, Aug 21, 2017 at 9:31 AM, Szabolcs Nagy <firstname.lastname@example.org> wrote:
>> On 08/08/17 17:40, H.J. Lu wrote:
>>> When building libc.a with PIE, enable hidden visibility to allow direct
>>> access to definitions within libc.a without using GOT.
>>> -#if defined SHARED || defined LIBC_NONSHARED
>>> +#if defined SHARED || defined LIBC_NONSHARED \
>>> + || (BUILD_PIE_DEFAULT && IS_IN (libc))
>>> # define attribute_hidden __attribute__ ((visibility ("hidden")))
>> btw what happens if this is enabled for non-pie libc.a ?
> It makes those symbols in libc.a hidden.
>> i'd expect that to work too (it prevents some symbol
> You can't interpose any symbols in libc.a, PIE or non-PIE.
> What my patch does is to avoid GOT/PLT in PIE libc.a when
> accessing them within libc.a.
yes, but my point is that the ifdef can be simplified
if it's valid for the non-pie case too.