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Re: Does gcc enable -fPIC by default?
- From: Alexander Monakov <amonakov at ispras dot ru>
- To: Peng Yu <pengyu dot ut at gmail dot com>
- Cc: "gcc-help at gcc dot gnu dot org" <gcc-help at gcc dot gnu dot org>
- Date: Thu, 24 Jan 2019 18:02:00 +0300 (MSK)
- Subject: Re: Does gcc enable -fPIC by default?
- References: <CABrM6wm9g=D==VUu-qm6Ahqn+J1DcfxeLDjW=iX9OH+F_yEExg@mail.gmail.com> <CABrM6wnfSqY2xwEL--6Gj2qOnzs-6TUC7=FaKm7QE4Z2q3KynA@mail.gmail.com>
On Thu, 24 Jan 2019, Peng Yu wrote:
> Is it because gcc enables -fPIC by default, but clang does not? I
> don't see this documented. Or it is due to some other reasons. On what
> systems gcc enables -fPIC by default?
There are platforms (e.g. Darwin) where all code is implicitly PIC by
convention (but there Clang will emit position-independent code as well),
but in your case the issue is likely because in your distribution GCC
is configured to produce PIE by default (see --enable-default-pie in
output of gcc -v):
> configure:3772: gcc -g -finstrument-functions
> -L/root/linux/bin/wrappercomposite/src/xplat/llvmxplat/src/mkvar/bin/Linux
> conftest.c -ltrace >&5
> /usr/bin/ld: /root/linux/bin/wrappercomposite/src/xplat/llvmxplat/src/mkvar/bin/Linux/libtrace.a(trace.o):
> relocation R_X86_64_32S against `.bss' can not be used when making a
> PIE object; recompile with -fPIC
^^^^^^^^^
(as the error message hints)
Hope that helps.
Alexander