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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Precompiled headers don't work with `#pragma once`"
href="https://llvm.org/bugs/show_bug.cgi?id=24387">24387</a>
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</tr>
<tr>
<th>Summary</th>
<td>Precompiled headers don't work with `#pragma once`
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.6
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</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>-New Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>hitchmanr@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>#pragma once information isn't stored in precompiled headers. This makes PCH
useless for projects that use #pragma once as the only form of header guard.
Test case:
a.h:
#pragma once
static int x = 3;
a.c:
#include "a.h"
int main(void) { return 0; }
then:
$ clang a.c -o a
$ clang a.h -o a.h.pch
a.h:1:9: warning: #pragma once in main file
#pragma once
^
1 warning generated.
$ clang -include-pch a.h.pch a.c -o a
In file included from a.c:1:
./a.h:3:12: error: redefinition of 'x'
static int x = 3;
^
./a.h:3:12: note: previous definition is here
static int x = 3;
^
1 error generated.</pre>
</div>
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