Changes/RPMMacrosForBuildFlags

RPM Macros for Build Flags

Summary

Create "extra flag" macros to make it easier for packages to add and remove compiler flags.

Owner

• Name: Tom Stellard
• Email: <tstellar@redhat.com>

Current status

• Targeted release: Fedora Linux 38
• Last updated: 2022-11-24
• devel thread
• FESCo issue: #2805
• Tracker bug: #2100610
• Release notes tracker: <will not assigned by the Wrangler -- not user-facing>

Detailed Description

The macros file in the redhat-rpm-config package contains a list of default compiler flags for packages to use when compiling C, C++, and Fortran packages. This change will add new macros to redhat-rpm-config which will make it easier for packages to add their own compiler flags.

The proposed macros for adding new flags are:

   %_pkg_extra_cflags
   %_pkg_extra_cxxflags
   %_pkg_extra_fflags
   %_pkg_extra_ldflags

These will be added to %{build_cflags}, %{build_cxxflags}, %{build_fflags}, and %{build_ldflags} respectively to allow packages to add their own flags to the default list: e.g.

   %build_cflags %{optflags} %{_pkg_extra_cflags}

This will also make it easier to experiment with system-wide compiler changes in Fedora as it will be possible to modify the default compiler flags without patching redhat-rpm-config.

Feedback

The original proposal would have replaced every existing compiler flag in redhat-rpm-config with it's own macro. However, it was determined that this may be a little bit too confusing since there would be ambiguity about whether, for example, %global _flag_f_exceptions %{nil} would actually disable exceptions by adding -fno-exceptions to the flags or if it would just remove the -fexceptions flag. Rather than hold up other useful and fairly straight-forward changes in this proposal, the proposal owners decided to drop the flag macro from this proposal. It could be revisited in a later release.

Benefit to Fedora

• It will provide a standard way to add to the list of default compiler flags.
• It will make it easier to determine which add compiler flags by doing a simple grep of the spec files.
• It will make it easier for toolchain developers to experiment with adding new flags to the distribution as this can be done with a simple macro definition instead of patching redhat-rpm-config.

Scope

• Proposal owners:
  • Proposal owners will update the redhat-rpm-config package and add the new macros.
  • Proposal owners will test the changes to ensure that the correct flags are still being used.

• Other developers:
  • Other developers may, but are not required to, update their packages to use the new macros.

• Release engineering: #10819

• Policies and guidelines:
  • The Fedora packaging policy will be updated to require that packages that want to use additional flag use the new macros.

• Trademark approval: N/A (not needed for this Change)

• Alignment with Objectives:

Upgrade/compatibility impact

None.

How To Test

• This can be tested by inspecting the value of the %{build_cflags}, %{build_cxxflags}, %{build_fflags}, and %{build_ldflags} and ensuring they are the same before and after the change.
• This can be tested by modifying some of the new macros in a spec file and ensuring that the changes appear in the appropriate macro mentioned above.

User Experience

This is a change for developers and will have no impact to the user experience.

Dependencies

None.

Contingency Plan

• Contingency mechanism: (What to do? Who will do it?) Change owner will revert the update to redhat-rpm-config.
• Contingency deadline: Mass Rebuild
• Blocks release? N/A (not a System Wide Change), No

Documentation

None.

Release Notes

None.