The INSTALL_BYPRODUCTS ExternalProject_Add() argument was only added in
CMake 3.26 and the current minimum is 3.20. Work around this by using an
explicit ExternalProject_Add_Step() call for the install step with a
BYPRODUCTS argument. We can't keep using the `install` name here since that
is reserved by the CMake implementation and results in errors when used.
This commit should be reverted once LLVM depends on CMake 3.26.
Pull Request: https://github.com/llvm/llvm-project/pull/115677
Using the build tree is somewhat fragile since the layout is not
guaranteed to be stable and means the tests are tightly coupled to the
libc++/libc++abi build tree layout. Instead update the ExternalProject
to install the library and headers and do not add the build tree to
the include/linker flags.
Pull Request: https://github.com/llvm/llvm-project/pull/115077
The runtimes used to support a build mode called the "Standalone build",
which isn't supported anymore (and hasn't been for a few years).
However, various places in the code still contained stuff whose only
purpose was to support that build mode, and some outdated documentation.
This patch cleans that up (although I probably missed some).
- Remove HandleOutOfTreeLLVM.cmake which isn't referenced anymore
- Remove the LLVM_PATH CMake variable which isn't used anymore
- Update some outdated documentation referencing standalone builds
I am currently trying to test the LLVM runtimes (including compiler-rt)
against an installed LLVM tree rather than a build tree (since that is
no longer available). Currently, the runtimes build of compiler-rt assumes
that LLVM_BINARY_DIR is writable since it uses configure_file() to write
there during the CMake configure stage. Instead, generate this file inside
CMAKE_CURRENT_BINARY_DIR, which will match LLVM_BINARY_DIR when invoked
from llvm/runtimes/CMakeLists.txt.
I also needed to make a minor change to the hwasan tests: hwasan_symbolize
was previously found in the LLVM_BINARY_DIR, but since it is generated as
part of the compiler-rt build it is now inside the CMake build directory
instead. I fixed this by passing the output directory to lit as
config.compiler_rt_bindir and using llvm_config.add_tool_substitutions().
For testing that we no longer write to the LLVM install directory as
part of testing or configuration, I created a read-only bind mount and
configured the runtimes builds as follows:
```
$ sudo mount --bind --read-only ~/llvm-install /tmp/upstream-llvm-readonly
$ cmake -DCMAKE_BUILD_TYPE=Debug \
-DCMAKE_C_COMPILER=/tmp/upstream-llvm-readonly/bin/clang \
-DCMAKE_CXX_COMPILER=/tmp/upstream-llvm-readonly/bin/clang++ \
-DLLVM_INCLUDE_TESTS=TRUE -DLLVM_ENABLE_ASSERTIONS=TRUE \
-DCOMPILER_RT_INCLUDE_TESTS=TRUE -DCOMPILER_RT_DEBUG=OFF \
-DLLVM_ENABLE_RUNTIMES=compiler-rt \
-DLLVM_BINARY_DIR=/tmp/upstream-llvm-readonly \
-G Ninja -S ~/upstream-llvm-project/runtimes \
-B ~/upstream-llvm-project/runtimes/cmake-build-debug-llvm-git
```
Reviewed By: ldionne
Pull Request: https://github.com/llvm/llvm-project/pull/86209
The profiling code requires GNU extensions as it uses functions such as getpagesize(), fdopen(), etc.
The problem manifests when the compiler is built to not default to the extensions mode, e.g. custom config with -std=c2x. CMake didn't support this scenario very well, but it's been fixed by CMP0128. Set the policy to NEW as we now conform to it.
Summary:
This patch adds initial support to build the `builtins` library for GPU
targets. Primarily this requires adding a few new architectures for
`amdgcn` and `nvptx64`. I built this using the following invocations.
```console
$ cmake ../compiler-rt -DCMAKE_C_COMPILER=clang
-DCMAKE_CXX_COMPILER=clang++ -DCMAKE_BUILD_TYPE=Release -GNinja
-DCMAKE_C_COMPILER_TARGET=<nvptx64-nvidia-cuda|amdgcn-amd-amdhsa>
-DCMAKE_CXX_COMPILER_TARGET=<nvptx64-nvidia-cuda|amdgcn-amd-amdhsa>
-DCMAKE_C_COMPILER_WORKS=1 -DCMAKE_CXX_COMPILER_WORKS=1
-DLLVM_CMAKE_DIR=../cmake/Modules -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
-C ../compiler-rt/cmake/caches/GPU.cmake
```
Some pointers would be appreciated for how to test this using a standard
(non-default target only) build.
GPU builds are somewhat finnicky. We only expect this to be built with a
sufficiently new clang, as it's the only compiler that supports the
target and output we distribute. Distribution is done as LLVM-IR blobs
for now.
GPUs have little backward compatibility, so linking object files is
left to a future patch.
More work is necessary to build correctly for all targets and ship into
the correct clang resource directory. Additionally we need to use the
`libc` project's support for running unit tests.
Update the folder titles for targets in the monorepository that have not
seen taken care of for some time. These are the folders that targets are
organized in Visual Studio and XCode
(`set_property(TARGET <target> PROPERTY FOLDER "<title>")`)
when using the respective CMake's IDE generator.
* Ensure that every target is in a folder
* Use a folder hierarchy with each LLVM subproject as a top-level folder
* Use consistent folder names between subprojects
* When using target-creating functions from AddLLVM.cmake, automatically
deduce the folder. This reduces the number of
`set_property`/`set_target_property`, but are still necessary when
`add_custom_target`, `add_executable`, `add_library`, etc. are used. A
LLVM_SUBPROJECT_TITLE definition is used for that in each subproject's
root CMakeLists.txt.
In https://github.com/llvm/llvm-project/pull/88323, I changed the logic
within `add_compiler_rt_runtime` to only explicitly code sign the
resulting library if an older version of Apple's ld64 was in use. This
was based on the assumption that newer versions of ld64 and the new
Apple linker always ad-hoc sign their output binaries. This is true in
most cases, but not when using Apple's new linker with the
`-darwin-target-variant` flag to build Mac binaries that are compatible
with Catalyst.
Rather than adding increasingly complicated logic to detect the exact
scenarios that require explicit code signing, I've opted to always
explicitly code sign when using any Apple linker. We instead detect and
use the 'linker-signed' codesigning option when possible to match the
signatures that the linker would otherwise create. This avoids having
non-'linker-signed' ad-hoc signatures which was the underlying problem
that https://github.com/llvm/llvm-project/pull/88323 was intended to
address.
Co-authored-by: Mark Rowe <markrowe@chromium.org>
This was added in def0823f1d2db78c4a18b15084407734a45e96c5 to fix a bot
failure, specifically for the standalone build. This does not seem to be
an issue anymore, and setting the policy explicitly to OLD causes
warnings with newer CMake versions.
This patch removes setting the policy to OLD to get rid of the warning.
Currently, the testsuite uses the default runtimes path to find the
runtimes libraries which may or may not match the just-built runtimes.
This change uses the `-resource-dir` flag for clang whenever
`COMPILER_RT_TEST_STANDALONE_BUILD_LIBS` is set to ensure that we are
actually testing the currently built libraries rather than the ones
bundled with `${COMPILER_RT_TEST_COMPILER}`.
The existing logic works fine when clang and compiler-rt share the same
build directory ``-DLLVM_ENABLE_PROJECTS=clang;compiler-rt`, but when
building compiler-rt separately we need to tell the compiler used for
the tests where it can find the just-built libraries.
This reduces the fixes check-all failures to one in my configuration:
```
cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo -G Ninja
-DCMAKE_C_COMPILER=$HOME/output/upstream-llvm/bin/clang
-DCMAKE_CXX_COMPILER=$HOME/output/upstream-llvm/bin/clang++
-DCOMPILER_RT_INCLUDE_TESTS=ON
-DLLVM_EXTERNAL_LIT=$HOME/build/upstream-llvm-project-build/bin/llvm-lit
-DLLVM_CMAKE_DIR=$HOME/output/upstream-llvm
-DCOMPILER_RT_DEBUG=OFF
-S $HOME/src/upstream-llvm-project/compiler-rt
-B $HOME/src/upstream-llvm-project/compiler-rt/cmake-build-all-sanitizers
```
This relands the previous PR with fixes for Windows.
Depends on https://github.com/llvm/llvm-project/pull/88074 to be merged
first for GCC buildbots.
Pull Request: https://github.com/llvm/llvm-project/pull/88075
Apple's new linker reports itself as ld rather than ld64 and does not
match the version detection regex.
Invert the logic to look only for older versions of ld64. This ensures
the runtime dylibs are left with a linker-generated code signature that
tools such as `strip` will preserve.
Co-authored-by: Mark Rowe <markrowe@chromium.org>
Currently, the testsuite uses the default runtimes path to find the
runtimes libraries which may or may not match the just-built runtimes.
This change uses the `-resource-dir` flag for clang whenever
`COMPILER_RT_TEST_STANDALONE_BUILD_LIBS` is set to ensure that we are
actually testing the currently built libraries rather than the ones
bundled with `${COMPILER_RT_TEST_COMPILER}`.
The existing logic works fine when clang and compiler-rt share the same
build directory ``-DLLVM_ENABLE_PROJECTS=clang;compiler-rt`, but when
building compiler-rt separately we need to tell the compiler used for
the tests where it can find the just-built libraries.
This reduces the fixes check-all failures to one in my configuration:
```
cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo -G Ninja
-DCMAKE_C_COMPILER=$HOME/output/upstream-llvm/bin/clang
-DCMAKE_CXX_COMPILER=$HOME/output/upstream-llvm/bin/clang++
-DCOMPILER_RT_INCLUDE_TESTS=ON
-DLLVM_EXTERNAL_LIT=$HOME/build/upstream-llvm-project-build/bin/llvm-lit
-DLLVM_CMAKE_DIR=$HOME/output/upstream-llvm
-DCOMPILER_RT_DEBUG=OFF
-S $HOME/src/upstream-llvm-project/compiler-rt
-B $HOME/src/upstream-llvm-project/compiler-rt/cmake-build-all-sanitizers
```
Reviewed By: vitalybuka, delcypher, MaskRay
Pull Request: https://github.com/llvm/llvm-project/pull/83088
When the top-level CMake invocation has `CMAKE_VERBOSE_MAKEFILE=ON`,
indicating the user wants to have verbose builds (i.e. all executed
commands explicitly echoed), some of the subprojects and runtimes (such
as compiler-rt, libcxx, etc) do not build in verbose mode. For example,
with Ninja:
```
[ 99% 6252/6308] cd /build/runtimes/builtins-bins && /usr/local/bin/cmake --build .
[ 0% 6/308] Building C object CMakeFiles/clang_rt.builtins-i386.dir/absvti2.c.o
[ 0% 7/308] Building C object CMakeFiles/clang_rt.builtins-i386.dir/absvdi2.c.o
[ 0% 8/308] Building C object CMakeFiles/clang_rt.builtins-i386.dir/absvsi2.c.o
...
```
This is because `llvm_ExternalProject_Add()` and `add_custom_libcxx()`
use CMake's `ExternalProject_Add()` function to configure such
subproject builds, and do not pass through the `CMAKE_VERBOSE_MAKEFILE`
setting.
Similar to what is done in `clang/CMakeLists.txt`, add
`-DCMAKE_VERBOSE_MAKEFILE=ON` to the `ExternalProject_Add()` invocations
in `llvm_ExternalProject_Add()` and `add_custom_libcxx()`, whenever the
top-level CMake invocation had `CMAKE_VERBOSE_MAKEFILE` turned on.
This can be used to configure runtimes builds (instead of setting flags
individually), and we need to pass it down to the custom libc++ build
for it to work correctly.
The Android LLVM build system builds the arm64 fuzzer lib without
HWASan, but then applications that enable HWASan can generated an object
file with a HWASan-ified version of some libc++ symbols (e.g.
`std::__1::piecewise_construct`). The linker can choose the HWASan-ified
definition, but then it cannot resolve the relocation from
libclang_rt.fuzzer-aarch64-android.a to this symbol because the high
bits of the address are unexpectedly set. This produces an error:
```
relocation R_AARCH64_ADR_PREL_PG_HI21 out of range
```
Fix this problem by linking a custom isolated libc++ into Android's
fuzzer library.
We need to pass through ANDROID_NATIVE_API_LEVEL so that the libc++ for
32-bit Android (API < 24) uses LLVM_FORCE_SMALLFILE_FOR_ANDROID.
Resolved issue with green dragon build by fixing relocations for
MachO/Darwin which doesn't compile without @page/@pageoff directives.
Also silenced a warning about constructor(90) priority being < 101,
which is reserved for the implementation. In this case, we're compiling
the implementation so we should be able to use 90.
This reverts commit 072713add4408199d4bce7b3b02cc74a4a382ee0.
When compiling for SME and using the attributes to use PSTATE.ZA,
Clang will emit calls to SME ABI support routines to save and
restore ZA state.
Reviewed By: paulwalker-arm
Differential Revision: https://reviews.llvm.org/D154045
CMake older than 3.20.0 is no longer supported.
This removes work-arounds for no longer supported versions.
Reviewed By: phosek
Differential Revision: https://reviews.llvm.org/D152102
Previously, an .exe suffix was only added for MSVC configurations.
In practice, an .exe suffix is added implicitly by MinGW toolchains
if the output is a suffixless file name. However this can cause lots
of subtle build system confusion, when it's not generating the file it
expected.
Differential Revision: https://reviews.llvm.org/D149029
If any LLVM subprojects are built separately, the LLVM build directory
LLVM_LIBRARY_DIR is added to both the build and install runpaths in
llvm_setup_rpath(), which is incorrect when installed. Separate the
build and install runpaths on ELF platforms and finally remove the
incorrect call to this function for compiler-rt, as previously attempted
in 21c008d5a5b. That prior attempt was reverted in 959dbd1761c, where it
was said to break the build on macOS and Windows, so I made sure to keep
those platforms the same.
Two examples of incorrect runpaths that are currently added, one from
the latest LLVM 16 toolchain for linux x86_64:
> readelf -d clang+llvm-16.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/16/lib/x86_64-unknown-linux-gnu/libclang_rt.*so | ag "File:|runpath"
File: clang+llvm-16.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/16/lib/x86_64-unknown-linux-gnu/libclang_rt.asan.so
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/tmp/llvm_release/final/Phase3/Release/llvmCore-16.0.0-final.obj/./lib]
File: clang+llvm-16.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/16/lib/x86_64-unknown-linux-gnu/libclang_rt.dyndd.so
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/tmp/llvm_release/final/Phase3/Release/llvmCore-16.0.0-final.obj/./lib]
File: clang+llvm-16.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/16/lib/x86_64-unknown-linux-gnu/libclang_rt.hwasan_aliases.so
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/tmp/llvm_release/final/Phase3/Release/llvmCore-16.0.0-final.obj/./lib]
File: clang+llvm-16.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/16/lib/x86_64-unknown-linux-gnu/libclang_rt.hwasan.so
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/tmp/llvm_release/final/Phase3/Release/llvmCore-16.0.0-final.obj/./lib]
File: clang+llvm-16.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/16/lib/x86_64-unknown-linux-gnu/libclang_rt.memprof.so
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/tmp/llvm_release/final/Phase3/Release/llvmCore-16.0.0-final.obj/./lib]
File: clang+llvm-16.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/16/lib/x86_64-unknown-linux-gnu/libclang_rt.scudo_standalone.so
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/tmp/llvm_release/final/Phase3/Release/llvmCore-16.0.0-final.obj/./lib]
File: clang+llvm-16.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/16/lib/x86_64-unknown-linux-gnu/libclang_rt.tsan.so
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/tmp/llvm_release/final/Phase3/Release/llvmCore-16.0.0-final.obj/./lib]
File: clang+llvm-16.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/16/lib/x86_64-unknown-linux-gnu/libclang_rt.ubsan_minimal.so
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/tmp/llvm_release/final/Phase3/Release/llvmCore-16.0.0-final.obj/./lib]
File: clang+llvm-16.0.0-x86_64-linux-gnu-ubuntu-18.04/lib/clang/16/lib/x86_64-unknown-linux-gnu/libclang_rt.ubsan_standalone.so
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/tmp/llvm_release/final/Phase3/Release/llvmCore-16.0.0-final.obj/./lib]
Another is in the Swift toolchain, which builds lldb separately:
> readelf -d swift-5.9-DEVELOPMENT-SNAPSHOT-2023-03-24-a-ubuntu20.04/usr/{bin/lldb*,lib/liblldb.so}|ag "File:|runpath"
File: swift-5.9-DEVELOPMENT-SNAPSHOT-2023-03-24-a-ubuntu20.04/usr/bin/lldb
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/home/build-user/build/buildbot_linux/llvm-linux-x86_64/./lib]
File: swift-5.9-DEVELOPMENT-SNAPSHOT-2023-03-24-a-ubuntu20.04/usr/bin/lldb-argdumper
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/home/build-user/build/buildbot_linux/llvm-linux-x86_64/./lib]
File: swift-5.9-DEVELOPMENT-SNAPSHOT-2023-03-24-a-ubuntu20.04/usr/bin/lldb-server
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/home/build-user/build/buildbot_linux/llvm-linux-x86_64/./lib]
File: swift-5.9-DEVELOPMENT-SNAPSHOT-2023-03-24-a-ubuntu20.04/usr/lib/liblldb.so
0x000000000000001d (RUNPATH) Library runpath: [$ORIGIN/../lib:/home/build-user/build/buildbot_linux/llvm-linux-x86_64/./lib:/home/build-user/build/buildbot_linux/swift-linux-x86_64/lib/swift/linux:$ORIGIN/../lib/swift/linux]
This patch should fix this problem of absolute paths from the build host
leaking out into the toolchain's runpaths.
Differential revision: https://reviews.llvm.org/D146918
This does not help. The build is broken because compiler-rt-clear
deletes cmake generated files in STAMP_DIR/
This reverts commit da89ed99a16920e5986b14853d297322ccf7109e.
Fixes the following on cmake version 3.24.2:
'tools/clang/runtime/compiler-rt-stamps/compiler-rt-source_dirinfo.txt',
needed by 'tools/clang/runtime/compiler-rt-stamps/compiler-rt-download',
missing and no known rule to make it
Maybe related to https://cmake.org/cmake/help/latest/release/3.24.html#modules
This re-applies bb939931a1ad, which had been reverted by 09cebfb978de
because it broke Chromium. The issues seen by Chromium should be
addressed by 1d0f79558ca4.
Differential Revision: https://reviews.llvm.org/D128927
This caused build failures when building Clang and libc++ together on Mac:
fatal error: 'experimental/memory_resource' file not found
See the code review for details. Reverting until the problem and how to
solve it is better understood.
(Updates to some test files were not reverted, since they seemed
unrelated and were later updated by 340b48b267b96.)
> This is the first part of a plan to ship experimental features
> by default while guarding them behind a compiler flag to avoid
> users accidentally depending on them. Subsequent patches will
> also encompass incomplete features (such as <format> and <ranges>)
> in that categorization. Basically, the idea is that we always
> build and ship the c++experimental library, however users can't
> use what's in it unless they pass the `-funstable` flag to Clang.
>
> Note that this patch intentionally does not start guarding
> existing <experimental/FOO> content behind the flag, because
> that would merely break users that might be relying on such
> content being in the headers unconditionally. Instead, we
> should start guarding new TSes behind the flag, and get rid
> of the existing TSes we have by shipping their Standard
> counterpart.
>
> Also, this patch must jump through a few hoops like defining
> _LIBCPP_ENABLE_EXPERIMENTAL because we still support compilers
> that do not implement -funstable yet.
>
> Differential Revision: https://reviews.llvm.org/D128927
This reverts commit bb939931a1adb9a47a2de13c359d6a72aeb277c8.
This is the first part of a plan to ship experimental features
by default while guarding them behind a compiler flag to avoid
users accidentally depending on them. Subsequent patches will
also encompass incomplete features (such as <format> and <ranges>)
in that categorization. Basically, the idea is that we always
build and ship the c++experimental library, however users can't
use what's in it unless they pass the `-funstable` flag to Clang.
Note that this patch intentionally does not start guarding
existing <experimental/FOO> content behind the flag, because
that would merely break users that might be relying on such
content being in the headers unconditionally. Instead, we
should start guarding new TSes behind the flag, and get rid
of the existing TSes we have by shipping their Standard
counterpart.
Also, this patch must jump through a few hoops like defining
_LIBCPP_ENABLE_EXPERIMENTAL because we still support compilers
that do not implement -funstable yet.
Differential Revision: https://reviews.llvm.org/D128927
We no longer support the use of LLVM_ENABLE_PROJECTS for libcxx and
libcxxabi. We don't use paths to libcxx and libcxxabi in compiler-rt.
Differential Revision: https://reviews.llvm.org/D126905
We no longer support the use of LLVM_ENABLE_PROJECTS for libcxx and
libcxxabi. We don't use paths to libcxx and libcxxabi in compiler-rt.
Differential Revision: https://reviews.llvm.org/D126905
This avoids the need for string-ification and lets CMake deduplicate
potentially duplicate flags.
Differential Revision: https://reviews.llvm.org/D122750
Similar to D120946, pass LIBCXX_HAS_GCC_S_LIB and LIBCXX_USE_COMPILER_RT
through to the custom lib++ builds so that libfuzzer doesn't end up with
a .deplibs section that links against those libraries when the
variables are set to false.
Reviewed By: phosek
Differential Revision: https://reviews.llvm.org/D127912
Apply this in add_compiler_rt_runtime instead of manually adding it
to the individual projects. This applies the option on more
parts of compiler-rt than before, but should ideally not make any
difference assuming the other runtimes that lacked the option
also were C11 compatible.
Not marking this as required, to match the existing behaviour (where
`-std=c11` was added only if supported by the compiler).
This was suggested during the review of D110005.
Differential Revision: https://reviews.llvm.org/D124343
Like D118875, but for ubsan, asan, etc.
With this, I can successfully run:
bin/clang++ -target x86_64-apple-ios14.0-macabi foo.cc \
-isysroot $(xcrun -show-sdk-path) -fsanitize=undefined
with a locally built libclang_rt.ubsan_osx_dynamic.dylib.
Differential Revision: https://reviews.llvm.org/D124059
ld64 implicitly ad-hoc code-signs as of Xcode 12, and `strip` and friends know
how keep this special ad-hoc signature valid.
So this should have no effective behavior change, except that you can now strip
libclang_rt.asan_osx_dynamic.dylib and it'll still have a valid ad-hoc
signature, instead of strip printing "warning: changes being made to the file
will invalidate the code signature in:" and making the ad-hoc code signature
invalid.
Differential Revision: https://reviews.llvm.org/D123475
This clarifies that this is an LLVM specific variable and avoids
potential conflicts with other projects.
Differential Revision: https://reviews.llvm.org/D119918
Pass LIBCXX_HAS_PTHREAD_LIB, LIBCXX_HAS_RT_LIB and LIBCXXABI_HAS_PTHREAD_LIB
through to the custom lib++ builds so that libfuzzer doesn't end up with a .deplibs section that
links against those libraries when the variables are set to false.
Reviewed By: phosek
Differential Revision: https://reviews.llvm.org/D120946
Note: the term "libgcc" refers to the all of `libgcc.a`, `libgcc_eh.a`,
and `libgcc_s.so`.
Enabling libunwind as a replacement for libgcc on Linux has proven to be
challenging since libgcc_s.so is a required dependency in the [Linux
standard base][5]. Some software is transitively dependent on libgcc
because glibc makes hardcoded calls to functions in libgcc_s. For example,
the function `__GI___backtrace` eventually makes its way to a [hardcoded
dlopen to libgcc_s' _Unwind_Backtrace][1]. Since libgcc_{eh.a,s.so} and
libunwind have the same ABI, but different implementations, the two
libraries end up [cross-talking, which ultimately results in a
segfault][2].
To solve this problem, libunwind needs to build a “libgcc”. That is, link
the necessary functions from compiler-rt and libunwind into an archive
and shared object that advertise themselves as `libgcc.a`, `libgcc_eh.a`,
and `libgcc_s.so`, so that glibc’s baked calls are diverted to the
correct objects in memory. Fortunately for us, compiler-rt and libunwind
use the same ABI as the libgcc family, so the problem is solvable at the
llvm-project configuration level: no program source needs to be edited.
Thus, the end result is for a user to configure their LLVM build with a
flag that indicates they want to archive compiler-rt/unwind as libgcc.
We achieve this by compiling libunwind with all the symbols necessary
for compiler-rt to emulate the libgcc family, and then generate symlinks
named for our "libgcc" that point to their corresponding libunwind
counterparts.
We alternatively considered patching glibc so that the source doesn't
directly refer to libgcc, but rather _defaults_ to libgcc, so that a
system preferring compiler-rt/libunwind can point to these libraries
at the config stage instead. Even if we modified the Linux standard
base, this alternative won't work because binaries that are built using
libgcc will still end up having crosstalk between the differing
implementations.
This problem has been solved in this manner for [FreeBSD][3], and this
CL has been tested against [Chrome OS][4].
[1]: https://github.com/bminor/glibc/blob/master/sysdeps/arm/backtrace.c#L68
[2]: https://bugs.chromium.org/p/chromium/issues/detail?id=1162190#c16
[3]: https://github.com/freebsd/freebsd-src/tree/main/lib/libgcc_s
[4]: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/2945947
[5]: https://refspecs.linuxbase.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/libgcc-s.html
Differential Revision: https://reviews.llvm.org/D108416
Follow-up to 458ead66dc37, which replaced the bespoke CMakeLists.txt
file for building a custom instrumented libc++ with an invocation of the
runtimes build.
In the the bespoke CMakeLists.txt, the LIBCXX_CXX_ABI setting was forced
to libcxxabi, but this was not done for the CMake invocation for the
runtimes build. This would cause CMake configuration issues on platforms
where the default LIBCXX_CXX_ABI setting is not libcxxabi, such as
FreeBSD.
Add `-DLIBCXX_CXX_ABI=libcxxabi` to that invocation, to make sure the
custom instrumented libc++ always uses the expected ABI.
Reviewed By: phosek
Differential Revision: https://reviews.llvm.org/D119554
Some of the compiler-rt runtimes use custom instrumented libc++ build.
Use the runtimes build for building this custom libc++.
Differential Revision: https://reviews.llvm.org/D114922
