Is there convenient way to setup Fedora compilation flags outside of the RPM build?

[Vít Ondruch]

Working with upstream on one issue [1], it seems that the culprit is in 
the Fedora compiler options. Is there some convenient way to set them 
up? Of course I can copy them from log, or somehow put together from the 
RPM macros, but I'd appreciate if there was some easier way. Can we e.g. 
distribute some script, which would set them up, as part or some RPM?


Vít



[1] https://bugs.ruby-lang.org/issues/19248

[Elliott Sales de Andrade]

On Fri, Dec 23, 2022 at 1:21 PM Vít Ondruch <vondruch(a)redhat.com&gt; wrote:
>  Working with upstream on one issue [1], it seems that the culprit is in
>  the Fedora compiler options. Is there some convenient way to set them
>  up? Of course I can copy them from log, or somehow put together from the
>  RPM macros, but I'd appreciate if there was some easier way. Can we e.g.
>  distribute some script, which would set them up, as part or some RPM?
>  
Now that we have the `set_build_flags` macro, it's somewhat
straightforward to do:

$ rpm -E '%set_build_flags'
  CFLAGS="${CFLAGS:--O2 -flto=auto -ffat-lto-objects -fexceptions -g
-grecord-gcc-switches -pipe -Wall -Werror=format-security
-Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS
-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1
-fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1
 -m64  -mtune=generic -fasynchronous-unwind-tables
-fstack-clash-protection -fcf-protection}" ; export CFLAGS ;
  CXXFLAGS="${CXXFLAGS:--O2 -flto=auto -ffat-lto-objects -fexceptions
-g -grecord-gcc-switches -pipe -Wall -Werror=format-security
-Wp,-D_FORTIFY_SOURCE=2 -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}" ; export CXXFLAGS ;
  FFLAGS="${FFLAGS:--O2 -flto=auto -ffat-lto-objects -fexceptions -g
-grecord-gcc-switches -pipe -Wall -Werror=format-security
-Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS
-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1
-fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1
 -m64  -mtune=generic -fasynchronous-unwind-tables
-fstack-clash-protection -fcf-protection
-I/usr/lib64/gfortran/modules}" ; export FFLAGS ;
  FCFLAGS="${FCFLAGS:--O2 -flto=auto -ffat-lto-objects -fexceptions -g
-grecord-gcc-switches -pipe -Wall -Werror=format-security
-Wp,-D_FORTIFY_SOURCE=2 -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
-I/usr/lib64/gfortran/modules}" ; export FCFLAGS ;
  LDFLAGS="${LDFLAGS:--Wl,-z,relro -Wl,--as-needed  -Wl,-z,now
-specs=/usr/lib/rpm/redhat/redhat-hardened-ld
-specs=/usr/lib/rpm/redhat/redhat-annobin-cc1  -Wl,--build-id=sha1 }"
; export LDFLAGS ;
  LT_SYS_LIBRARY_PATH="${LT_SYS_LIBRARY_PATH:-/usr/lib64:}" ; export
LT_SYS_LIBRARY_PATH ;
  CC="${CC:-gcc}" ; export CC ;
  CXX="${CXX:-g++}" ; export CXX

So you can do
$ eval `rpm -E '%set_build_flags'`
in a script to set the flags that RPM uses.

>
> Vít
>

[Artur Frenszek-Iwicki]

>  So you can do
>  $ eval `rpm -E '%set_build_flags'`
>  in a script to set the flags that RPM uses. 
Another solution could be something
like:
$ gcc $(rpm -E '%optflags') ... $(rpm -E '%build_ldflags') 

A.FI.

[Florian Weimer]

* Vít Ondruch:

>  Working with upstream on one issue [1], it seems that the culprit is
> in 
>  the Fedora compiler options. Is there some convenient way to set them 
>  up? Of course I can copy them from log, or somehow put together from the 
>  RPM macros, but I'd appreciate if there was some easier way. Can we e.g. 
>  distribute some script, which would set them up, as part or some RPM? 
Build systems and test harnesses often tweak the build flags, so it's
probably best to enable logging there to see what's going on.

Different distributions also have different compiler defaults.  For
example, most of Fedora's explicit compiler flags are enabled by
default in Ubuntu's GCC.

[Vít Ondruch]

Dne 24. 12. 22 v 20:49 Florian Weimer napsal(a):
>  * Vít Ondruch:
>
> > Working with upstream on one issue [1], it seems that the culprit is in
> > the Fedora compiler options. Is there some convenient way to set them
> > up? Of course I can copy them from log, or somehow put together from the
> > RPM macros, but I'd appreciate if there was some easier way. Can we e.g.
> > distribute some script, which would set them up, as part or some RPM?
>  Build systems and test harnesses often tweak the build flags, so it's
>  probably best to enable logging there to see what's going on.
>  

Of course the build flags can be seen from the build log, but precisely 
for the reason that "Build systems and test harnesses often tweak the 
build flags", I'd like to have easy way to provide upstream with the 
default Fedora build flags.


>  Different distributions also have different compiler defaults.  For
>  example, most of Fedora's explicit compiler flags are enabled by
>  default in Ubuntu's GCC.
>
>  
And yes, that is the problem why upstream can't see the issues we see, 
despite they were so kind to test on Fedora. Luckily, there was analysis 
of the issue which initially triggered this discussion done by Mamoru 
[1] and it seem that the issue are caused by LTO. Nevertheless, if there 
was some way to tell them lets say:

1) $ sudo dnf install fedora-official-build-flags

2) $ with-fedora-official-build-flags make

That would be super convenient and I still find surprising we don't have 
anything like this.


Vít


[1] https://bugs.ruby-lang.org/issues/19248#note-14

[Florian Weimer]

* Vít Ondruch:

>  And yes, that is the problem why upstream can't see the issues we
> see,
>  despite they were so kind to test on Fedora. Luckily, there was
>  analysis of the issue which initially triggered this discussion done
>  by Mamoru [1] and it seem that the issue are caused by
>  LTO. Nevertheless, if there was some way to tell them lets say:
>
>  1) $ sudo dnf install fedora-official-build-flags
>
>  2) $ with-fedora-official-build-flags make
>
>  That would be super convenient and I still find surprising we don't
>  have anything like this. 
After installing redhat-rpm-config, this works in bash and similar
shells:

$ eval `rpm --eval %set_build_flags`

Maybe we can make it more clear in buildflags.md that this macro is a
shell script fragment?

Thanks,
Florian

[Vít Ondruch]

Dne 02. 01. 23 v 14:09 Florian Weimer napsal(a):
>  * Vít Ondruch:
>
> > And yes, that is the problem why upstream can't see the issues we see,
> > despite they were so kind to test on Fedora. Luckily, there was
> > analysis of the issue which initially triggered this discussion done
> > by Mamoru [1] and it seem that the issue are caused by
> > LTO. Nevertheless, if there was some way to tell them lets say:
> >
> > 1) $ sudo dnf install fedora-official-build-flags
> >
> > 2) $ with-fedora-official-build-flags make
> >
> > That would be super convenient and I still find surprising we don't
> > have anything like this.
>  After installing redhat-rpm-config, this works in bash and similar
>  shells:
>
>  $ eval `rpm --eval %set_build_flags`
>
>  Maybe we can make it more clear in buildflags.md that this macro is a
>  shell script fragment?
>  

My gut answer was something about "who reads the documentation", but 
since I was referring to the buildflags.md in the issue, then this could 
be probably good start :D

But still, if there was something I can remember or even find via e.g. 
tab completion, that would be much better.


Vít

>  Thanks,
>  Florian
>
>

[Sam Varshavchik]

Florian Weimer writes:

>  After installing redhat-rpm-config, this works in bash and similar
>  shells:
>
>  $ eval `rpm --eval %set_build_flags`
>
>  Maybe we can make it more clear in buildflags.md that this macro is a
>  shell script fragment? 
I find it more convenient to generate parameters for an autoconf-generated  
configure script. I do not need to always use the same build flags as rpm.  
Sometimes you want to build without optimizations, for debugging purposes.

What I do is

./configure `rpmflags`

with "rpmflags" being this script:

#! /bin/bash

echo -n "CXXFLAGS='"
rpm -E '%build_cxxflags' | tr -d '\012'
echo -n "' CFLAGS='"
rpm -E '%build_cflags' | sed 's/ *$//' | tr -d '\012'
echo -n "' LDFLAGS='"
rpm -E '%build_ldflags' | sed 's/ *$//' | tr -d '\012'
echo "'"

I suppose I can turn this inside-out, and change this to use  
%set_build_flags and directly run configure.

[Vitaly Zaitsev]

On 23/12/2022 19:21, Vít Ondruch wrote:
>  Working with upstream on one issue [1], it seems that the culprit is
> in 
>  the Fedora compiler options. Is there some convenient way to set them up? 
rpm -E %optflags

-- 
Sincerely,
   Vitaly Zaitsev (vitaly(a)easycoding.org)

[Sam Varshavchik]

Vitaly Zaitsev via devel writes:

>  On 23/12/2022 19:21, Vít Ondruch wrote:
> > Working with upstream on one issue [1], it seems that the culprit is in the  
> > Fedora compiler options. Is there some convenient way to set them up?
>
>  rpm -E %optflags 
rpm -E '%__global_ldflags'

is also needed for LDFLAGS.

[Maxwell G]

On Sun Dec 25, 2022 at 09:02 -0500, Sam Varshavchik wrote:
>  rpm -E '%__global_ldflags'
>
>  is also needed for LDFLAGS. 
%__global_ldflags is deprecated. You should use %build_ldflags
instead[1]. Also, %build_cflags, %build_cxxflags, and friends are
preferred to %optflags AFAIK.

[1]: https://src.fedoraproject.org/rpms/redhat-rpm-config/blob/rawhide/f/macro...
--
Maxwell G (@gotmax23)
Pronouns: He/Him/His