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clang-p2996/lld/docs/ReleaseNotes.rst
Daniel Thornburgh 074af0f30f [lld][ELF] Add --why-live flag (inspired by Mach-O) (#127112)
This prints a stack of reasons that symbols that match the given glob(s)
survived GC. It has no effect unless section GC occurs.

This implementation does not require -ffunction-sections or
-fdata-sections to produce readable results, althought it does tend to
work better (as does GC).

Details about the semantics:
- Some chain of liveness reasons is reported; it isn't specified which
chain.
 - A symbol or section may be live:
   - Intrisically (e.g., entry point)
   - Because needed by a live symbol or section
   - (Symbols only) Because part of a section live for another reason
   - (Sections only) Because they contain a live symbol
 - Both global and local symbols (`STB_LOCAL`) are supported.
 - References to symbol + offset are considered to point to:
   - If the referenced symbol is a section (`STT_SECTION`):
- If a sized symbol encloses the referenced offset, the enclosing
symbol.
     - Otherwise, the section itself, generically.
   - Otherwise, the referenced symbol.
2025-03-26 09:56:33 -07:00

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===========================
lld |release| Release Notes
===========================
.. contents::
:local:
.. only:: PreRelease
.. warning::
These are in-progress notes for the upcoming LLVM |release| release.
Release notes for previous releases can be found on
`the Download Page <https://releases.llvm.org/download.html>`_.
Introduction
============
This document contains the release notes for the lld linker, release |release|.
Here we describe the status of lld, including major improvements
from the previous release. All lld releases may be downloaded
from the `LLVM releases web site <https://llvm.org/releases/>`_.
Non-comprehensive list of changes in this release
=================================================
ELF Improvements
----------------
* For AArch64, added support for ``-zgcs-report-dynamic``, enabling checks for
GNU GCS Attribute Flags in Dynamic Objects when GCS is enabled. Inherits value
from ``-zgcs-report`` (capped at ``warning`` level) unless user-defined,
ensuring compatibility with GNU ld linker.
* The default Hexagon architecture version in ELF object files produced by
lld is changed to v68. This change is only effective when the version is
not provided in the command line by the user and cannot be inferred from
inputs.
* ``--why-live=<glob>`` prints for each symbol matching ``<glob>`` a chain of
items that kept it live during garbage collection. This is inspired by the
Mach-O LLD feature of the same name.
Breaking changes
----------------
COFF Improvements
-----------------
MinGW Improvements
------------------
MachO Improvements
------------------
WebAssembly Improvements
------------------------
Fixes
#####