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Fangrui Song b4744d306c [ELF] Support --{,no-}allow-shlib-undefined 
Summary:
In ld.bfd/gold, --no-allow-shlib-undefined is the default when linking
an executable. This patch implements a check to error on undefined
symbols in a shared object, if all of its DT_NEEDED entries are seen.

Our approach resembles the one used in gold, achieves a good balance to
be useful but not too smart (ld.bfd traces all DSOs and emulates the
behavior of a dynamic linker to catch more cases).

The error is issued based on the symbol table, different from undefined
reference errors issued for relocations. It is most effective when there
are DSOs that were not linked with -z defs (e.g. when static sanitizers
runtime is used).

gold has a comment that some system libraries on GNU/Linux may have
spurious undefined references and thus system libraries should be
excluded (https://sourceware.org/bugzilla/show_bug.cgi?id=6811). The
story may have changed now but we make --allow-shlib-undefined the
default for now. Its interaction with -shared can be discussed in the
future.

Reviewers: ruiu, grimar, pcc, espindola

Reviewed By: ruiu

Subscribers: joerg, emaste, arichardson, llvm-commits

Differential Revision: https://reviews.llvm.org/D57385

llvm-svn: 352826
 		2019-02-01 02:25:05 +00:00
..
COFF Fix names of functions in TargetOptionsCommandFlags.h. NFC. 2019-02-01 02:24:50 +00:00
Common Fix names of functions in TargetOptionsCommandFlags.h. NFC. 2019-02-01 02:24:50 +00:00
ELF [ELF] Support --{,no-}allow-shlib-undefined 2019-02-01 02:25:05 +00:00
MinGW [MinGW] Don't define names for ignored options. NFC. 2019-01-29 19:24:32 +00:00
cmake/modules [CMake] Properly conditionalize installation of lld libraries 2018-03-09 13:09:36 +00:00
docs Adjust documentation for git migration. 2019-01-29 16:37:27 +00:00
include/lld Fix names of functions in TargetOptionsCommandFlags.h. NFC. 2019-02-01 02:24:50 +00:00
lib Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
test [ELF] Support --{,no-}allow-shlib-undefined 2019-02-01 02:25:05 +00:00
tools/lld Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
unittests Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
utils Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
wasm Fix names of functions in TargetOptionsCommandFlags.h. NFC. 2019-02-01 02:24:50 +00:00
.arcconfig [lld] Set up .arcconfig to point to new Diffusion LLD repository 2017-12-06 20:56:23 +00:00
.clang-format
…
.gitignore
…
CMakeLists.txt [WebAssembly] Initial wasm linker implementation 2017-11-17 18:14:09 +00:00
CODE_OWNERS.TXT [WebAssembly] Initial wasm linker implementation 2017-11-17 18:14:09 +00:00
LICENSE.TXT Fix typos throughout the license files that somehow I and my reviewers 2019-01-21 09:52:34 +00:00
README.md Note that the test .tar.xz has been updated. 2017-12-22 19:37:32 +00:00

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.