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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - error: unknown argument: '-m32 -DLIBCXX_BUILDING_LIBCXXABI' when building 32-bit libc++ on x86_64/Linux"
href="https://bugs.llvm.org/show_bug.cgi?id=49294">49294</a>
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<th>Summary</th>
<td>error: unknown argument: '-m32 -DLIBCXX_BUILDING_LIBCXXABI' when building 32-bit libc++ on x86_64/Linux
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<th>Product</th>
<td>libc++
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>manojgupta@google.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
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<div>
<pre>I am seeing a bunch of error: unknown argument: '-m32
-DLIBCXX_BUILDING_LIBCXXABI' when building 32-bit libc++ on x86_64/Linux.
Repro steps:
1. Build clang and compiler-rt builtins
$ cd /path/to/llvm-project
$ mkdir ../build && cd ../build
$ cmake ../llvm-project/llvm
-DLLVM_ENABLE_PROJECTS="llvm;clang;lld;compiler-rt"
$ ninja clang builtins
$
2. Try to build 32-bit libc++ as standalone library
(We are in llvm-project/../build directory)
$ mkdir libcxx_build && cd libcxx_build
$ cmake -GNinja ../../llvm-project/libcxx "-DLLVM_USE_LINKER=lld"
-DCMAKE_C_COMPILER=/path/to/build/bin/clang
-DCMAKE_CXX_COMPILER=/path/to/build/bin/clang++ -DCMAKE_BUILD_TYPE=Release
"-DLIBCXX_USE_COMPILER_RT=ON" "-DLIBCXX_BUILD_32_BITS=ON"
"-DLIBCXX_CXX_ABI=libcxxabi"
"-DLIBCXX_CXX_ABI_INCLUDE_PATHS=../../llvm-project/libcxxabi/include"
I see following messages in the logs that look surprising. Seems like somewhere
"-m32" and "-DLIBCXX_BUILDING_LIBCXXABI" were combined as a single compiler
option which is causing clang to reject the option.
clang-12: error: unknown argument: '-m32 -DLIBCXX_BUILDING_LIBCXXABI'
-- Failed to find compiler-rt library
clang-12: error: unknown argument: '-m32 -DLIBCXX_BUILDING_LIBCXXABI'
-- Failed to find compiler-rt library
clang-12: error: unknown argument: '-m32 -DLIBCXX_BUILDING_LIBCXXABI'
-- Failed to find compiler-rt library
This does not cause any build breakage but I believe there is some incorrect
compiler flag handling somewhere.</pre>
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