<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/118982>118982</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
How to fully build llvm-libc
</td>
</tr>
<tr>
<th>Labels</th>
<td>
libc
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
icuxika
</td>
</tr>
</table>
<pre>
I want to build libc according to the [Full Host Build](https://libc.llvm.org/full_host_build.html), but there are some configurations that I don't understand well.
```
SYSROOT=/home/icuxika/CommandLineTools/llvm-fullbuild
cmake -S llvm -B build -G Ninja -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;lldb;lld" -DLLVM_ENABLE_RUNTIMES="libc;compiler-rt;libcxx;libcxxabi;libunwind" -DDEFAULT_SYSROOT=$SYSROOT -DCMAKE_INSTALL_PREFIX=$SYSROOT -DCMAKE_BUILD_TYPE=Release -DLLVM_PARALLEL_COMPILE_JOBS=12 -DLLVM_PARALLEL_LINK_JOBS=4 -DLLVM_LIBC_FULL_BUILD=ON -DLLVM_LIBC_INCLUDE_SCUDO=ON -DCOMPILER_RT_BUILD_SCUDO_STANDALONE_WITH_LLVM_LIBC=ON -DCOMPILER_RT_BUILD_GWP_ASAN=OFF -DCOMPILER_RT_SCUDO_STANDALONE_BUILD_SHARED=OFF
```
> I tried to build using the above command, but it ended up saying that the header file of the standard library could not be found.
##
- llvm version 19.1.5
- os Ubuntu 22.04.5 LTS
## Question
1. Should` SYSROOT` point to an empty directory? Or point to a compiled llvm directory? Or download and unzip the directory from GitHub release?
2. Will not using `lld` and `compiler-rt` affect this build?
3. Will using gcc and g++ affect this build?
## build err log
```
CMakeFiles/clang_rt.builtins-i386.dir/eprintf.c.o
/home/icuxika/Source/llvm-project-llvmorg-19.1.5/build/./bin/clang --target=x86_64-unknown-linux-gnu -DVISIBILITY_HIDDEN -O3 -DNDEBUG -m32 -fno-lto -std=c11 -fPIC -fno-builtin -fvisibility=hidden -fomit-frame-pointer -DCOMPILER_RT_HAS_FLOAT16 -MD -MT CMakeFiles/clang_rt.builtins-i386.dir/eprintf.c.o -MF CMakeFiles/clang_rt.builtins-i386.dir/eprintf.c.o.d -o CMakeFiles/clang_rt.builtins-i386.dir/eprintf.c.o -c /home/icuxika/Source/llvm-project-llvmorg-19.1.5/compiler-rt/lib/builtins/eprintf.c
/home/icuxika/Source/llvm-project-llvmorg-19.1.5/compiler-rt/lib/builtins/eprintf.c:10:10: fatal error: 'stdio.h' file not found
10 | #include <stdio.h>
| ^~~~~~~~~
1 error generated.
[103/316] Building C object CMakeFiles/clang_rt.builtins-i386.dir/emutls.c.o
FAILED: CMakeFiles/clang_rt.builtins-i386.dir/emutls.c.o
/home/icuxika/Source/llvm-project-llvmorg-19.1.5/build/./bin/clang --target=x86_64-unknown-linux-gnu -DVISIBILITY_HIDDEN -O3 -DNDEBUG -m32 -fno-lto -std=c11 -fPIC -fno-builtin -fvisibility=hidden -fomit-frame-pointer -DCOMPILER_RT_HAS_FLOAT16 -MD -MT CMakeFiles/clang_rt.builtins-i386.dir/emutls.c.o -MF CMakeFiles/clang_rt.builtins-i386.dir/emutls.c.o.d -o CMakeFiles/clang_rt.builtins-i386.dir/emutls.c.o -c /home/icuxika/Source/llvm-project-llvmorg-19.1.5/compiler-rt/lib/builtins/emutls.c
/home/icuxika/Source/llvm-project-llvmorg-19.1.5/compiler-rt/lib/builtins/emutls.c:10:10: fatal error: 'stdlib.h' file not found
10 | #include <stdlib.h>
| ^~~~~~~~~~
1 error generated.
[104/316] Building C object CMakeFiles/clang_rt.builtins-i386.dir/enable_execute_stack.c.o
FAILED: CMakeFiles/clang_rt.builtins-i386.dir/enable_execute_stack.c.o
/home/icuxika/Source/llvm-project-llvmorg-19.1.5/build/./bin/clang --target=x86_64-unknown-linux-gnu -DVISIBILITY_HIDDEN -O3 -DNDEBUG -m32 -fno-lto -std=c11 -fPIC -fno-builtin -fvisibility=hidden -fomit-frame-pointer -DCOMPILER_RT_HAS_FLOAT16 -MD -MT CMakeFiles/clang_rt.builtins-i386.dir/enable_execute_stack.c.o -MF CMakeFiles/clang_rt.builtins-i386.dir/enable_execute_stack.c.o.d -o CMakeFiles/clang_rt.builtins-i386.dir/enable_execute_stack.c.o -c /home/icuxika/Source/llvm-project-llvmorg-19.1.5/compiler-rt/lib/builtins/enable_execute_stack.c
/home/icuxika/Source/llvm-project-llvmorg-19.1.5/compiler-rt/lib/builtins/enable_execute_stack.c:12:10: fatal error: 'sys/mman.h' file not found
12 | #include <sys/mman.h>
| ^~~~~~~~~~~~
1 error generated.
[108/316] Building C object CMakeFiles/clang_rt.builtins-i386.dir/cpu_model/x86.c.o
FAILED: CMakeFiles/clang_rt.builtins-i386.dir/cpu_model/x86.c.o
/home/icuxika/Source/llvm-project-llvmorg-19.1.5/build/./bin/clang --target=x86_64-unknown-linux-gnu -DVISIBILITY_HIDDEN -O3 -DNDEBUG -m32 -fno-lto -std=c11 -fPIC -fno-builtin -fvisibility=hidden -fomit-frame-pointer -DCOMPILER_RT_HAS_FLOAT16 -MD -MT CMakeFiles/clang_rt.builtins-i386.dir/cpu_model/x86.c.o -MF CMakeFiles/clang_rt.builtins-i386.dir/cpu_model/x86.c.o.d -o CMakeFiles/clang_rt.builtins-i386.dir/cpu_model/x86.c.o -c /home/icuxika/Source/llvm-project-llvmorg-19.1.5/compiler-rt/lib/builtins/cpu_model/x86.c
/home/icuxika/Source/llvm-project-llvmorg-19.1.5/compiler-rt/lib/builtins/cpu_model/x86.c:24:10: fatal error: 'assert.h' file not found
24 | #include <assert.h>
| ^~~~~~~~~~
1 error generated.
[110/316] Building C object CMakeFiles/clang_rt.builtins-i386.dir/clear_cache.c.o
FAILED: CMakeFiles/clang_rt.builtins-i386.dir/clear_cache.c.o
/home/icuxika/Source/llvm-project-llvmorg-19.1.5/build/./bin/clang --target=x86_64-unknown-linux-gnu -DVISIBILITY_HIDDEN -O3 -DNDEBUG -m32 -fno-lto -std=c11 -fPIC -fno-builtin -fvisibility=hidden -fomit-frame-pointer -DCOMPILER_RT_HAS_FLOAT16 -MD -MT CMakeFiles/clang_rt.builtins-i386.dir/clear_cache.c.o -MF CMakeFiles/clang_rt.builtins-i386.dir/clear_cache.c.o.d -o CMakeFiles/clang_rt.builtins-i386.dir/clear_cache.c.o -c /home/icuxika/Source/llvm-project-llvmorg-19.1.5/compiler-rt/lib/builtins/clear_cache.c
/home/icuxika/Source/llvm-project-llvmorg-19.1.5/compiler-rt/lib/builtins/clear_cache.c:11:10: fatal error: 'assert.h' file not found
11 | #include <assert.h>
| ^~~~~~~~~~
1 error generated.
[118/316] Building C object CMakeFiles/clang_rt.builtins-i386.dir/gcc_personality_v0.c.o
ninja: build stopped: subcommand failed.
FAILED: runtimes/builtins-stamps/builtins-build /home/icuxika/Source/llvm-project-llvmorg-19.1.5/build/runtimes/builtins-stamps/builtins-build
cd /home/icuxika/Source/llvm-project-llvmorg-19.1.5/build/runtimes/builtins-bins && /usr/local/bin/cmake --build .
ninja: build stopped: subcommand failed.
```
</pre>
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