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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 - rerunning cmake causes binaries to be relinked regardless of repo changes"
href="https://bugs.llvm.org/show_bug.cgi?id=33717">33717</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>rerunning cmake causes binaries to be relinked regardless of repo changes
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</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>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>matthias.krueger@famsik.de
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Running cmake causes binaries to be relinked even if neither repo files nor
cmake config changed since last build, this is quite strange and a huge time
sink in case of LTO builds.
I don't clearly remember this behaviour being present a week or two ago.
I can repro like this:
After doing an initial build:
cd build_dir
ninja-build clang LLVMgold llvm-ar llvm-ranlib lld
=> no files are rebuilt, everything ok
However if I run cmake before (as part my build script):
cd build_dir
cmake ../llvm -G "Ninja" \
-DCMAKE_BUILD_TYPE=Release \
-DLLVM_BINUTILS_INCDIR=/usr/include \
-DCMAKE_C_FLAGS="-march=native -O3 -g0 -DNDEBUG" \
-DCMAKE_CXX_FLAGS="-march=native -O3 -g0 -DNDEBUG" \
-DLLVM_PARALLEL_LINK_JOBS=1 \
-DLLVM_TARGETS_TO_BUILD="X86" \
-DLLVM_OPTIMIZED_TABLEGEN=1 \
-DLLVM_BUILD_TOOLS=0
ninja-build clang LLVMgold llvm-ar llvm-ranlib lld
=> these 12 files will be rebuilt:
lib/Object/CMakeFiles/LLVMObject.dir/IRSymtab.cpp.o
lib/libLLVMObject.a
bin/llvm-ar
bin/llvm-ranlib
bin/clang-offload-bundler
lib/LTO/CMakeFiles/LLVMLTO.dir/ThinLTOCodeGenerator.cpp.o
lib/LTO/CMakeFiles/LLVMLTO.dir/LTO.cpp.o
lib/libLLVMLTO.a
lib/LLVMgold.so
bin/clang-5.0
bin/clang
bin/lld
In case of tests (check-llvm check-clang check-lld), 72 targets are being
rebuilt every time
Now for "normal" builds this is not a huge issue but in case of lto, this can
prolong subsequent builds by several hours. :/
Did anyone else run into this?
Said script:
<a href="https://github.com/matthiaskrgr/llvm_bootstrap/blob/master/build_git.sh">https://github.com/matthiaskrgr/llvm_bootstrap/blob/master/build_git.sh</a>
cmake 3.5
ninja-build 1.7.2</pre>
</div>
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