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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - libc++ 13.0 still depends on "libgcc_s.so" even when it's built with "-DLIBCXX_USE_COMPILER_RT=ON""
href="https://bugs.llvm.org/show_bug.cgi?id=52083">52083</a>
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</tr>
<tr>
<th>Summary</th>
<td>libc++ 13.0 still depends on "libgcc_s.so" even when it's built with "-DLIBCXX_USE_COMPILER_RT=ON"
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>zin.kosmos.1190@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr></table>
<p>
<div>
<pre>## Overview
When I build llvm project 13.0.0 (which includes libc++) using cmake with
"-DLIBCXX_USE_COMPILER_RT=ON" options, libc++ still depends on "libgcc_s.so.1".
But according to the clang document "Assembling a Complete Toolchain" (
<a href="https://clang.llvm.org/docs/Toolchain.html#compiler-rt-llvm">https://clang.llvm.org/docs/Toolchain.html#compiler-rt-llvm</a>), libc++ uses
compiler-rt rather than libgcc with the cmake options.
## System environment
OS: 5.11.0-37-generic #41~20.04.2-Ubuntu
cmake: version 3.21.3
ninja: 1.10.2
## Steps to Reproduce
1. Download "llvm-project-13.0.0.src.tar.xz"
(<a href="https://github.com/llvm/llvm-project/releases/download/llvmorg-13.0.0/llvm-project-13.0.0.src.tar.xz">https://github.com/llvm/llvm-project/releases/download/llvmorg-13.0.0/llvm-project-13.0.0.src.tar.xz</a>)
and "clang+llvm-12.0.0-x86_64-linux-gnu-ubuntu-20.04.tar.xz" (
<a href="https://github.com/llvm/llvm-project/releases/download/llvmorg-12.0.0/clang+llvm-12.0.0-x86_64-linux-gnu-ubuntu-20.04.tar.xz">https://github.com/llvm/llvm-project/releases/download/llvmorg-12.0.0/clang+llvm-12.0.0-x86_64-linux-gnu-ubuntu-20.04.tar.xz</a>).
We use "clang+llvm-12.0.0-x86_64-linux-gnu-ubuntu-20.04" to build
"llvm-project-13.0.0".
2. Extract "clang+llvm-12.0.0-x86_64-linux-gnu-ubuntu-20.04.tar.xz" and set
path to the clang binary,
```
export
PATH=${path-to-clang+llvm-12.0.0-x86_64-linux-gnu-ubuntu-20.04}/bin:${PATH}
```
3. Extract "llvm-project-13.0.0.src.tar.xz" and build it using cmake and ninja
```
mkdir build
cd build
CC=clang CXX=clang++ cmake -GNinja -DCMAKE_BUILD_TYPE=Release
-DCMAKE_INSTALL_PREFIX=${PWD}/clang-nodeps
-DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;compiler-rt;libclc;libcxx;libcxxabi;libunwind;lld;lldb;mlir;openmp;parallel-libs;polly;pstl"
-DCOMPILER_RT_USE_BUILTINS_LIBRARY=ON -DLIBCXXABI_USE_COMPILER_RT=ON
-DLIBCXXABI_USE_LLVM_UNWINDER=ON -DLIBCXX_USE_COMPILER_RT=ON
-DLIBUNWIND_USE_COMPILER_RT=ON ../llvm
cmake --build . --config Release --target install --parallel
```
4. Check dependencies using ldd
```
ldd ./clang-nodeps/lib/libc++.so.1
```
## Actual Result
ldd shows the libc++ depends on "libgcc_s.so.1",
```
linux-vdso.so.1 (0x00007fffaa1ec000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0
(0x00007f5843ef8000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f5843d06000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f5843bb7000)
librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f5843bac000)
libatomic.so.1 => /lib/x86_64-linux-gnu/libatomic.so.1
(0x00007f5843ba2000)
libc++abi.so.1 => /home/sho/local/clang-nodeps/lib/libc++abi.so.1
(0x00007f5843b5f000)
libunwind.so.1 => /home/sho/local/clang-nodeps/lib/libunwind.so.1
(0x00007f5843b4f000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1
(0x00007f5843b34000)
/lib64/ld-linux-x86-64.so.2 (0x00007f5844001000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f5843b2e000)
```
## Expected Result
This is the ldd result of libc++ 12.0.1 which doesn't depend on
"libgcc_s.so.1",
```
linux-vdso.so.1 (0x00007fff0309a000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0
(0x00007f0dbb5c8000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f0dbb3d6000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f0dbb287000)
librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f0dbb27c000)
libatomic.so.1 => /lib/x86_64-linux-gnu/libatomic.so.1
(0x00007f0dbb272000)
libc++abi.so.1 => /home/sho/local/clang-nodeps/lib/libc++abi.so.1
(0x00007f0dbb22f000)
libunwind.so.1 => /home/sho/local/clang-nodeps/lib/libunwind.so.1
(0x00007f0dbb21f000)
/lib64/ld-linux-x86-64.so.2 (0x00007f0dbb6d1000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f0dbb219000)
```
## Additional information
I also noticed libc++ 13.0 still depends on libatomic.so.1.
But according to the clang document "Assembling a Complete
Toolchain"(<a href="https://clang.llvm.org/docs/Toolchain.html#id1">https://clang.llvm.org/docs/Toolchain.html#id1</a>), compiler-rt is used
instead of libatomic when llvm is built with compiler-rt options.</pre>
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