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Re: [PATCH] Enable hidden visibility in libc.a compiled with PIE
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Date: Mon, 14 Aug 2017 05:51:58 -0700
- Subject: Re: [PATCH] Enable hidden visibility in libc.a compiled with PIE
- Authentication-results: sourceware.org; auth=none
- References: <20170808164040.GA31184@gmail.com>
On Tue, Aug 8, 2017 at 9:40 AM, H.J. Lu <hongjiu.lu@intel.com> wrote:
> When building libc.a with PIE, enable hidden visibility to allow direct
> access to definitions within libc.a without using GOT.
>
> Size comparison of elf/ldconfig when the compiler defaults to -fPIE:
>
> On x86-64:
> text data bss dec hex
> Before: 619206 20132 5488 644826 9d6da
> After : 619062 20132 5488 644682 9d64a
> On i686:
> text data bss dec hex
> Before: 556305 10816 3056 570177 8b341
> After : 553688 10756 3056 567500 8a8cc
>
> OK for master?
>
> H.J.
> ---
> * include/libc-symbols.h (attribute_hidden): Enable hidden
> visibility in libc.a compiled with PIE.
> ---
> include/libc-symbols.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/libc-symbols.h b/include/libc-symbols.h
> index fe3ab81c51..d6a1c260f6 100644
> --- a/include/libc-symbols.h
> +++ b/include/libc-symbols.h
> @@ -363,7 +363,8 @@ for linking")
> strong_alias(real, name)
> #endif
>
> -#if defined SHARED || defined LIBC_NONSHARED
> +#if defined SHARED || defined LIBC_NONSHARED \
> + || (BUILD_PIE_DEFAULT && IS_IN (libc))
> # define attribute_hidden __attribute__ ((visibility ("hidden")))
> #else
> # define attribute_hidden
> --
> 2.13.4
>
Any comments or objections?
--
H.J.