Re: -D_FORTIFY_SOURCE defined but value is too low [-Werror]

[Siddhesh Poyarekar]

On Mon, Jan 16, 2023 at 1:05 PM Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote:
>  I'm getting the strange error in $SUBJECT in an upstream CI job that
>  is targetting Fedora rawhide. I'm guessing it is something related to
>  the recent changes to set the  _FOTIFY_SOURCE value to 3 instead of
>  2, but not sure what.
>
>  What I'm finding especially bizarre is that I can't reproduce it on
>  rawhide myself, despite using the exact same package versions and
>  base container.
>
>  I can't even figure out which particular component is emitting this
>  error message string. My only thought is that perhaps it could be
>  ccache related, since upstream CI has ccache enabled and the cache
>  is preserved across CI pipelines. That could explain why I can't
>  reproduce myself.
>
>  My app has a config.h file used by all sources that does
>
>    #if !defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__
>    # define _FORTIFY_SOURCE 2
>    #endif
>
>  but the -D_FORTIFY_SOURCE=3 set by RPM in CFLAGS on the gcc command
>  line ought to override this fine.
>
>  $ gcc -Ilibvirt-glib/libvirt-glib-1.0.so.0.4000.0.p -Ilibvirt-glib -I../libvirt-glib -I.
> -I.. -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/sysprof-4
> -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -std=gnu99 ...snip
> many -Wxxx flags... -fexceptions -fasynchronous-unwind-tables -fipa-pure-const 
> -fstack-protector-strong -O2 -flto=auto -ffat-lto-objects -fexceptions -g
> -grecord-gcc-switches -pipe  -U_FORTIFY_SOURCE -Wp,-U_FORTIFY_SOURCE
> -Wp,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS
> -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong
> -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic
> -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection
> -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -fPIC -pthread
> '-DLOCALEDIR="/usr/share/locale"'
> '-DDATADIR="/usr/share"' -DLIBVIRT_GLIB_BUILD
> -DGLIB_VERSION_MIN_REQUIRED=GLIB_VERSION_2_48 -DGLIB_VERSION_MAX_ALLOWED=GLIB_VERSION_2_48
> -MD -MQ libvirt-glib/libvirt-glib-1.0.so.0.4000.0.p/libvirt-glib-error.c.o -MF
> libvirt-glib/libvirt-glib-1.0.so.0.4000.0.p/libvirt-glib-error.c.o.d -o
> libvirt-glib/libvirt-glib-1.0.so.0.4000.0.p/libvirt-glib-error.c.o -c
> ../libvirt-glib/libvirt-glib-error.c
>  ../libvirt-glib/libvirt-glib-error.c: error: -D_FORTIFY_SOURCE defined but value is too
> low [-Werror]
>  cc1: all warnings being treated as errors
>
>  So does anyone know what this error message would be coming from, and more
>  importantly how to make it go away :-) 
I've seen this happen with ccache is in use[1], which flips the
defines around, causing _FORTIFY_SOURCE to be undefined.  I've posted
a fix to redhat-rpm-config[2] to remedy this in the default flags to
work around the reordering; the additional -U was redundant anyway.

Sid

[1] https://bugzilla.redhat.com/show_bug.cgi?id=2160275
[2] https://src.fedoraproject.org/rpms/redhat-rpm-config/pull-request/237