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Use update-alternatives for /usr/bin/cc
Summary
Modify the gcc package so that the /usr/bin/cc and /usr/bin/c++ symlinks are managed by update-alternatives. This will allow users to
Owner
- Name: Tom Stellard
- Email: <tstellar@redhat.com>
Current status
- Targeted release: Fedora 32
- Last updated: 2019-12-11
- Tracker bug: <will be assigned by the Wrangler>
- Release notes tracker: <will be assigned by the Wrangler>
Detailed Description
The gcc package currently installs symlinks to /usr/bin/cc and /usr/bin/c++ which point to /usr/bin/gcc and /usr/bin/g++ respectively. For this change, the gcc package will be modified so that the update-alternatives creates these symlinks.
In addition to modifying the gcc package, the clang package will also be modified so that /usr/bin/clang and /usr/bin/clang++ can be used as alternatives for /usr/bin/cc /usr/bin/c++. The clang alternatives will have a lower priority than the gcc alternatives, so that by default, gcc will provide the /usr/bin/cc and /usr/bin/c++ implementations.
The clang package currently has a run-time dependency on gcc, so this ensures that gcc will always provide the default implementation, because it's impossible to install clang without gcc.
The only way users will be able to change the /usr/bin/cc or /usr/bin/c++ implementations will be by explicitly making this change using the update-alternatives tool.
Benefit to Fedora
Many build systems default to using /usr/bin/cc and /usr/bin/c++ as the default C/C++ compilers. Being able to easily swap out these implementation will provide a lot of flexibility within Fedora for doing things like setting up alternative buildroots for testing or adding a wrapper script around gcc to aid in implementing some kinds of system wide changes like changes to the default compiler flags.
Scope
- Proposal owners: tstellar
The proposal owner will implement the necessary changes in the gcc and clang packages.
- Other developers: N/A (not a System Wide Change)
The gcc maintainers will be responsible for reviewing and approving changes to the gcc package.
- Release engineering: #Releng issue number (a check of an impact with Release Engineering is needed)
- Policies and guidelines: No policies or guidelines will need to be updated as a result of this change.
- Trademark approval: N/A (not needed for this Change)
Upgrade/compatibility impact
This change should not impact upgradeability.
How To Test
Gating tests will be added to the gcc package to ensure that /usr/bin/cc and /usr/bin/c++ still point to /usr/bin/gcc and /usr/bin/g++ when installed. There will also be a gating test added to the clang package to ensure that /usr/bin/gcc and /usr/bin/g++ remain the default when clang is installed.
User Experience
This change will give users a much better way to experiment using other compilers for their own development. They will be able to easily switch between different compilers without having to modify their projects build system or make non-standard changes to their Fedora system.
Dependencies
N/A (not a System Wide Change)
Contingency Plan
- Contingency mechanism: (What to do? Who will do it?) Proposal Owner will revert changes made to gcc and clang packages and rebuild.
- Contingency deadline: If the changes are not complete by 2 weeks before the mass rebuild, then we will consider postponing to the next Fedora release and back out any changes that were made.
- Blocks release? No
- Blocks product? None
Documentation
N/A (not a System Wide Change)