Revision as of 20:24, 2 July 2018

Remove Excessive Linking

Summary

Pass --as-needed flag the linker through default system-wide LDFLAGS.

Owner

Name: Igor Gnatenko
Email: ignatenkobrain@fedoraproject.org
Release notes owner:

Current status

Targeted release: Fedora 29
Last updated: 2018-07-02
Tracker bug: <will be assigned by the Wrangler>

Detailed Description

The flag (--as-needed) tells the linker to link in the produced binary only the libraries containing symbols actually used by the binary itself. This binary can be either a final executale or another library.

The use of the --as-needed flag allows the linker to avoid linking extra libraries in a binary. This not only improves startup times (as the loader does not have to load all the libraries for every step) but might avoid the full initialization of big frameworks.

Benefit to Fedora

No real tests on Fedora has been made, so no real numbers in this section. But theoretically,

Better startup times (since loader doesn't have to load all the libraries)
Smaller metadata (since less dependencies are recorded in final binaries)

Scope

Proposal owners: Add -Wl,--as-needed into RPM_LD_FLAGS (in redhat-rpm-config).
Other developers: Nothing should break, but immediate work-around would be to disable this flag (will be provided in redhat-rpm-config) and fix real issue later.
Release engineering: #Releng issue number (mass rebuild is desired after this change).
- List of deliverables: N/A (not a System Wide Change)
Policies and guidelines: Add information how to turn it off (TODO link to FPC ticket).
Trademark approval: N/A (not needed for this Change)

Upgrade/compatibility impact

None for end-users. Developers which build their own packages might notice and should be guided how to fix / workaround issue.

How To Test

Install newest redhat-rpm-config package and build your package.

User Experience

See Benefit to Fedora section.

Dependencies

None.

Contingency Plan

Contingency mechanism: Owners will revert change in redhat-rpm-config and make it opt-in rather than opt-out.
Contingency deadline: Beta freeze.
Blocks release? No
Blocks product? Everything

Documentation

Only Packaging Guidelines needs to be updated.

Release Notes

@@ Line 1: / Line 1: @@
-<!-- Self Contained or System Wide Change Proposal?
+= Remove Excessive Linking =
-Use this guide to determine to which category your proposed change belongs to.
-Self Contained Changes are:
-* changes to isolated/leaf package without the impact on other packages/rest of the distribution
-* limited scope changes without the impact on other packages/rest of the distribution
-* coordinated effort within SIG with limited impact outside SIG functional area, accepted by the SIG
-System Wide Changes are:
-* changes that does not fit Self Contained Changes category touching
-* changes that require coordination within the distribution (for example mass rebuilds, release engineering or other teams effort etc.)
-* changing system defaults
-For Self Contained Changes, sections marked as "REQUIRED FOR SYSTEM WIDE CHANGES" are OPTIONAL but FESCo/Wrangler can request more details (especially in case the change proposal category is
-improper or updated to System Wide category). For System Wide Changes all fields on this form are required for FESCo acceptance (when applies).
-We request that you maintain the same order of sections so that all of the change proposal pages are uniform.
--->
-<!-- The actual name of your proposed change page should look something like: Changes/Your_Change_Proposal_Name.  This keeps all change proposals in the same namespace -->
-<!-- The actual name of your proposed change page should look something like: Changes/Your_Change_Proposal_Name.  This keeps all change proposals in the same namespace -->
-= Remove Excessive Linking <!-- The name of your change proposal --> =
 == Summary ==
-<!-- A sentence or two summarizing what this change is and what it will do. This information is used for the overall changeset summary page for each release. -->
+Pass <code>--as-needed</code> flag the linker through default system-wide LDFLAGS.
 == Owner ==
-<!--
-For change proposals to qualify as self-contained, owners of all affected packages need to be included here. Alternatively, a SIG can be listed as an owner if it owns all affected packages.
-This should link to your home wiki page so we know who you are.
--->
 * Name: [[User:ignatenkobrain|Igor Gnatenko]]
-<!-- Include you email address that you can be reached should people want to contact you about helping with your change, status is requested, or technical issues need to be resolved. If the change proposal is owned by a SIG, please also add a primary contact person. -->
 * Email: ignatenkobrain@fedoraproject.org
 * Release notes owner: <!--- To be assigned by docs team [[User:FASAccountName| Release notes owner name]] <email address> -->
-<!--- UNCOMMENT only for Changes with assigned Shepherd (by FESCo)
-* FESCo shepherd: [[User:FASAccountName| Shehperd name]] <email address>
--->
-<!--- UNCOMMENT only if this Change aims specific product, working group (Cloud, Workstation, Server, Base, Env & Stacks)
-* Product:
-* Responsible WG:
--->
 == Current status ==
 * Targeted release: [[Releases/29|Fedora 29]]
-* Last updated: <!-- this is an automatic macro — you don't need to change this line -->  {{REVISIONYEAR}}-{{REVISIONMONTH}}-{{REVISIONDAY2}}
+* Last updated: {{REVISIONYEAR}}-{{REVISIONMONTH}}-{{REVISIONDAY2}}
-<!-- After the change proposal is accepted by FESCo, tracking bug is created in Bugzilla and linked to this page
-Bugzilla states meaning as usual:
-NEW -> change proposal is submitted and announced
-ASSIGNED -> accepted by FESCo with on going development
-MODIFIED -> change is substantially done and testable
-ON_QA -> change is code completed and could be tested in the Beta release (optionally by QA)
-CLOSED as NEXTRELEASE -> change is completed and verified and will be delivered in next release under development
--->
 * Tracker bug: <will be assigned by the Wrangler>
 == Detailed Description ==
+The flag (<code>--as-needed</code>) tells the linker to link in the produced binary only the libraries containing symbols actually used by the binary itself. This binary can be either a final executale or another library.
-<!-- Expand on the summary, if appropriate.  A couple sentences suffices to explain the goal, but the more details you can provide the better. -->
+The use of the <code>--as-needed</code> flag allows the linker to avoid linking extra libraries in a binary. This not only improves startup times (as the loader does not have to load all the libraries for every step) but might avoid the full initialization of big frameworks.
 == Benefit to Fedora ==
+No real tests on Fedora has been made, so no real numbers in this section. But theoretically,
-<!-- What is the benefit to the platform?  If this is a major capability update, what has changed?  If this is a new functionality, what capabilities does it bring? Why will Fedora become a better distribution or project because of this proposal?-->
+* Better startup times (since loader doesn't have to load all the libraries)
+* Smaller metadata (since less dependencies are recorded in final binaries)
 == Scope ==
-* Proposal owners:
+* Proposal owners: Add <code>-Wl,--as-needed</code> into RPM_LD_FLAGS (in redhat-rpm-config).
-<!-- What work do the feature owners have to accomplish to complete the feature in time for release?  Is it a large change affecting many parts of the distribution or is it a very isolated change? What are those changes?-->
+* Other developers: Nothing should break, but immediate work-around would be to disable this flag (will be provided in redhat-rpm-config) and fix real issue later.
+* Release engineering: [https://pagure.io/releng/issues #Releng issue number] (mass rebuild is desired after this change).
-* Other developers: N/A (not a System Wide Change) <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-<!-- What work do other developers have to accomplish to complete the feature in time for release?  Is it a large change affecting many parts of the distribution or is it a very isolated change? What are those changes?-->
-* Release engineering: [https://pagure.io/releng/issues #Releng issue number] (a check of an impact with Release Engineering is needed) <!-- REQUIRED FOR SYSTEM WIDE AS WELL AS FOR SELF CONTAINED CHANGES -->
-<!-- Does this feature require coordination with release engineering (e.g. changes to installer image generation or update package delivery)?  Is a mass rebuild required?  include a link to the releng issue.
-The issue is required to be filed prior to feature submission, to ensure that someone is on board to do any process development work and testing, and that all changes make it into the pipeline; a bullet point in a change is not sufficient communication -->
 ** [[Fedora_Program_Management/ReleaseBlocking/Fedora{{FedoraVersionNumber|next}}|List of deliverables]]: N/A (not a System Wide Change) <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-<!-- Please check the list of Fedora release deliverables and list all the differences the feature brings -->
 * Policies and guidelines: Add information how to turn it off (TODO link to FPC ticket).
-<!-- Do the packaging guidelines or other documents need to be updated for this feature?  If so, does it need to happen before or after the implementation is done?  If a FPC ticket exists, add a link here. -->
 * Trademark approval: N/A (not needed for this Change)
-<!-- If your Change may require trademark approval (for example, if it is a new Spin), file a ticket ( https://fedorahosted.org/council/ ) requesting trademark approval from the Fedora Council. This approval will be done via the Council's consensus-based process. -->
 == Upgrade/compatibility impact ==
-<!-- What happens to systems that have had a previous versions of Fedora installed and are updated to the version containing this change? Will anything require manual configuration or data migration? Will any existing functionality be no longer supported? -->
 None for end-users. Developers which build their own packages might notice and should be guided how to fix / workaround issue.
 == How To Test ==
-<!-- This does not need to be a full-fledged document. Describe the dimensions of tests that this change implementation is expected to pass when it is done.  If it needs to be tested with different hardware or software configurations, indicate them.  The more specific you can be, the better the community testing can be.
+Install newest redhat-rpm-config package and build your package.
-Remember that you are writing this how to for interested testers to use to check out your change implementation - documenting what you do for testing is OK, but it's much better to document what *I* can do to test your change.
-A good "how to test" should answer these four questions:
-. What special hardware / data / etc. is needed (if any)?
-. How do I prepare my system to test this change? What packages
-need to be installed, config files edited, etc.?
-. What specific actions do I perform to check that the change is
-working like it's supposed to?
-. What are the expected results of those actions?
--->
-<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-N/A (not a System Wide Change)
 == User Experience ==
-<!-- If this change proposal is noticeable by its target audience, how will their experiences change as a result?  Describe what they will see or notice. -->
+See Benefit to Fedora section.
-<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-N/A (not a System Wide Change)
 == Dependencies ==
-<!-- What other packages (RPMs) depend on this package?  Are there changes outside the developers' control on which completion of this change depends?  In other words, completion of another change owned by someone else and might cause you to not be able to finish on time or that you would need to coordinate?  Other upstream projects like the kernel (if this is not a kernel change)? -->
+None.
-<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-N/A (not a System Wide Change)
 == Contingency Plan ==
+* Contingency mechanism: Owners will revert change in redhat-rpm-config and make it opt-in rather than opt-out.
-<!-- If you cannot complete your feature by the final development freeze, what is the backup plan?  This might be as simple as "Revert the shipped configuration".  Or it might not (e.g. rebuilding a number of dependent packages).  If you feature is not completed in time we want to assure others that other parts of Fedora will not be in jeopardy.  -->
+* Contingency deadline: Beta freeze.
-* Contingency mechanism: (What to do?  Who will do it?) N/A (not a System Wide Change)  <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+* Blocks release? No
-<!-- When is the last time the contingency mechanism can be put in place?  This will typically be the beta freeze. -->
+* Blocks product? Everything
-* Contingency deadline: N/A (not a System Wide Change)  <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-<!-- Does finishing this feature block the release, or can we ship with the feature in incomplete state? -->
-* Blocks release? N/A (not a System Wide Change), Yes/No <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-* Blocks product? product <!-- Applicable for Changes that blocks specific product release/Fedora.next -->
 == Documentation ==
-<!-- Is there upstream documentation on this change, or notes you have written yourself?  Link to that material here so other interested developers can get involved. -->
+Only Packaging Guidelines needs to be updated.
-<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-N/A (not a System Wide Change)
 == Release Notes ==
@@ Line 140: / Line 60: @@
 -->
-[[Category:ChangePageIncomplete]]
+[[Category:ChangePageReadyForWrangler]]
-<!-- When your change proposal page is completed and ready for review and announcement -->
-<!-- remove Category:ChangePageIncomplete and change it to Category:ChangeReadyForWrangler -->
-<!-- The Wrangler announces the Change to the devel-announce list and changes the category to Category:ChangeAnnounced (no action required) -->
-<!-- After review, the Wrangler will move your page to Category:ChangeReadyForFesco... if it still needs more work it will move back to Category:ChangePageIncomplete-->
-<!-- Select proper category, default is Self Contained Change -->
-<!-- [[Category:SelfContainedChange]] -->
 [[Category:SystemWideChange]]

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