Thanks for your report and patch.

This is fixed slightly differently for glibc 2.16 with:

commit 05c2c9618f583ea4acd69b3fe5ae2a2922dd2ddc
Author: Roland Mc Grath <roland@hack.frob.com>
Date:   Tue May 8 19:44:57 2012 +0200

    Warn if user requests __FORTIFY_SOURCE but it is disabled
    
    [BZ #13979]
            * include/features.h: Warn if user requests __FORTIFY_SOURCE
            checking but the checks are disabled for any reason.

Thanks.  I'll update Fedora's repo appropriately.

This #warning appears to be causing more grief than it is solving; for example, see this autoconf thread that complains that it is breaking configure scripts, and therefore Debian's decision to revert this patch in their build of glibc:

https://lists.gnu.org/archive/html/autoconf/2013-05/msg00003.html
http://anonscm.debian.org/viewvc/pkg-glibc/glibc-package/trunk/debian/patches/any/local-revert-bz13979.diff?revision=5553&view=markup

Eric, could you summarize the situation and email libc-alpha about this, please?

I wonder why this only now hits us - Fedora seems to be using this for some time already - don't they use FORTIFY_SOURCE checking?

Fedora uses it; I recall a bit of a disturbance when that change went in, but I believe the package owners bit the bullet and updated appropriately.

I did not found a thread on libc-alpha. How situation now looks?

Linux Arch still suffers from warnings flood produced by this code.

We have following disto-wide compilation variables:

CPPFLAGS="-D_FORTIFY_SOURCE=2"
CFLAGS="-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector
--param=ssp-buffer-size=4"

and compilation produces a lot of warnings in almost any c++ project:

/usr/include/features.h:328:4: warning: #warning _FORTIFY_SOURCE
requires compiling with optimization (-O) [-Wcpp]
 #  warning _FORTIFY_SOURCE requires compiling with optimization (-O)

What is the action item for us, downstream package maintainers? What we suppose to do? There were several proposals (see link to autoconf discussion above):

- revert commit 05c2c9618f5
- move _FORTIFY_SOURCE to CFLAGS/CXXFLAGS/..
- move -O2 to CPPFLAGS

Could you please give us advice on what solution is the best one.

(In reply to Anatol Pomozov from comment #7)
> Linux Arch still suffers from warnings flood produced by this code.
> 
> We have following disto-wide compilation variables:
> 
> CPPFLAGS="-D_FORTIFY_SOURCE=2"
> CFLAGS="-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector
> --param=ssp-buffer-size=4"
> 
> and compilation produces a lot of warnings in almost any c++ project:

Can you double-check if you set CXXFLAGS?  And if not, figure out why?

I try to build Thrift package for Arch and here are envvars at the moment of build:

LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro
SHELL=/bin/bash
TERM=xterm
MAKEFLAGS=-j4
CPPFLAGS=-D_FORTIFY_SOURCE=2
OLDPWD=/build/thrift/src
USER=builduser
COMMAND_MODE=legacy
SUDO_USER=root
SUDO_UID=0
CXXFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong --param=ssp-buffer-size=4
USERNAME=builduser
MAIL=/var/mail/builduser
PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl
CHOST=x86_64-unknown-linux-gnu
PWD=/build/thrift/src/thrift-0.9.2
LANG=C
SHLVL=1
SUDO_COMMAND=/usr/bin/makepkg -s --noconfirm -L --holdver -i
HOME=/build
CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong --param=ssp-buffer-size=4
LOGNAME=builduser
TEXTDOMAIN=pacman-scripts
SUDO_GID=0
TEXTDOMAINDIR=/usr/share/locale
_=/usr/bin/env


And here is command that generate warning:

libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I../../.. -I../../../lib/cpp/src/thrift -I../../cpp/src -I/usr/include -I./gen-cpp -D_FORTIFY_SOURCE=2 -g -MT libtestgencpp_la-ThriftTest_constants.lo -MD -MP -MF .deps/libtestgencpp_la-ThriftTest_constants.Tpo -c gen-cpp/ThriftTest_constants.cpp  -fPIC -DPIC -o .libs/libtestgencpp_la-ThriftTest_constants.o
In file included from /usr/include/c++/4.9.2/x86_64-unknown-linux-gnu/bits/os_defines.h:39:0,
                 from /usr/include/c++/4.9.2/x86_64-unknown-linux-gnu/bits/c++config.h:430,
                 from /usr/include/c++/4.9.2/iosfwd:38,
                 from gen-cpp/ThriftTest_types.h:10,
                 from gen-cpp/ThriftTest_constants.h:10,
                 from gen-cpp/ThriftTest_constants.cpp:7:
/usr/include/features.h:328:4: warning: #warning _FORTIFY_SOURCE requires compiling with optimization (-O) [-Wcpp]
 #  warning _FORTIFY_SOURCE requires compiling with optimization (-O)
    ^


hmm... libtool does not seems to use CXXFLAGS here.

(In reply to Anatol Pomozov from comment #9)
> hmm... libtool does not seems to use CXXFLAGS here.

Yes, so the warning is absolutely warranted here because the CXXFLAGS-based compiler flags injection does not work for some reason.

Digging deeper into Thrift build system I found that they just drop CFLAGS. It is wrong imho. Sent a patch upstream https://github.com/apache/thrift/pull/284

Sorry for the noise.

I am going to look why other packages have this warning.