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llvm / llvm-project / lld / f97e188d8eb7cc4a7f65e365a9c3d16b2e52aae0
commitf97e188d8eb7cc4a7f65e365a9c3d16b2e52aae0[log] [tgz]
authorNico Weber <thakis@chromium.org>Thu Feb 25 19:56:31 2021 -0500
committerCopybara-Service <copybara-worker@google.com>Fri Feb 26 22:04:14 2021 -0800
tree9205c0a1ba4d7cfdb3b8816001f22f9cd06ef73a
parent183315165e6b757c62ee03cf8b29ea8fb924f234 [diff]
[lld/mac] Add some support for dynamic lookup symbols, and implement -U

Dynamic lookup symbols are symbols that work like dynamic symbols
in ELF: They're not bound to a dylib like normal Mach-O twolevel lookup
symbols, but they live in a global pool and dyld resolves them against
exported symbols from all loaded dylibs.

This adds support for dynamical lookup symbols to lld/mac. They are
represented as DylibSymbols with file set to nullptr.

This also uses this support to implement the -U flag, which makes
a specific symbol that's undefined at the end of the link a
dynamic lookup symbol.

For -U, it'd be sufficient to just to a pass over remaining undefined symbols
at the end of the link and to replace them with dynamic lookup symbols then.
But I'd like to use this code to implement flat_namespace too, and that will
require real support for resolving dynamic lookup symbols in SymbolTable. So
this patch adds this now already.

While writing tests for this, I noticed that we didn't set N_WEAK_DEF in the
symbol table for DylibSymbols, so this fixes that too.

Differential Revision: https://reviews.llvm.org/D97521

GitOrigin-RevId: cafb6cd10c7434fdb541a40eda89fc51880f43c0
8 files changed
tree: 9205c0a1ba4d7cfdb3b8816001f22f9cd06ef73a
  1. cmake/
  2. COFF/
  3. Common/
  4. docs/
  5. ELF/
  6. include/
  7. lib/
  8. MachO/
  9. MinGW/
  10. test/
  11. tools/
  12. unittests/
  13. utils/
  14. wasm/
  15. .clang-format
  16. .clang-tidy
  17. .gitignore
  18. CMakeLists.txt
  19. CODE_OWNERS.TXT
  20. LICENSE.TXT
  21. README.md
README.md

LLVM Linker (lld)

This directory and its subdirectories contain source code for the LLVM Linker, a modular cross platform linker which is built as part of the LLVM compiler infrastructure project.

lld is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt.

Benchmarking

In order to make sure various developers can evaluate patches over the same tests, we create a collection of self contained programs.

It is hosted at https://s3-us-west-2.amazonaws.com/linker-tests/lld-speed-test.tar.xz

The current sha256 is 10eec685463d5a8bbf08d77f4ca96282161d396c65bd97dc99dbde644a31610f.