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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - CMAKE_BUILD_TYPE is blank by default (the current attempt to set to Debug is broken)"
href="https://llvm.org/bugs/show_bug.cgi?id=26666">26666</a>
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<th>Summary</th>
<td>CMAKE_BUILD_TYPE is blank by default (the current attempt to set to Debug is broken)
</td>
</tr>
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<th>Product</th>
<td>Build scripts
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>cmake
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>bruening@google.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>When configuring with cmake, the code attempts to set CMAKE_BUILD_TYPE to Debug
if it is not explicitly set. However, this is incorrectly done prior to the
project() command, which clears it out. The result is that CMAKE_BUILD_TYPE is
blank, which leads to a strange build that is something in between Release and
Debug but is missing assertions and much debug info.
The page at <a href="http://llvm.org/docs/GettingStarted.html">http://llvm.org/docs/GettingStarted.html</a> says:
"-DCMAKE_BUILD_TYPE=type — Valid options for type are Debug, Release,
RelWithDebInfo, and MinSizeRel. Default is Debug."
References elsewhere also assume that CMAKE_BUILD_TYPE is never blank: e.g., in
<a class="bz_bug_link
bz_status_NEW "
title="NEW --- - trivial (no options) CMake build fails"
href="show_bug.cgi?id=23322">https://llvm.org/bugs/show_bug.cgi?id=23322</a>.
To reproduce, simply compare these two:
# cmake -DCMAKE_BUILD_TYPE=Debug <path-to-sources>
# cmake <path-to-sources>
Notice how only the former sets -D_DEBUG (look in the makefiles or build.ninja
for -GNinja) and enables LLVM_ENABLE_ASSERTIONS, while the latter enables
"-Wl,-O3 -Wl,--gc-sections". The former results in a 22GB build directory
(this is llvm + clang) while the latter is only 4.1GB.
It looks like the code that tries to set a default was added in
<a href="http://reviews.llvm.org/D7360">http://reviews.llvm.org/D7360</a> but I do not understand how it ever worked. I
tested with cmake 2.8.10 as well as several other versions and it's always
blanked by project().
The fix is simple: move the current code that sets a blank type down below
project(). I will send a patch.</pre>
</div>
</p>
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