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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 --- - "foo.h" headers cause cyclic dependency between 'std' and 'Darwin' modules"
href="https://llvm.org/bugs/show_bug.cgi?id=25341">25341</a>
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<th>Summary</th>
<td>"foo.h" headers cause cyclic dependency between 'std' and 'Darwin' modules
</td>
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<th>Product</th>
<td>libc++
</td>
</tr>
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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
</td>
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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>
</tr>
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<th>Component</th>
<td>All Bugs
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>cdavis5x@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Ever since Richard started adding wrappers to libc++ for the standard C headers
("foo.h" headers, as he calls them), there's been a cyclic dependency between
the master libc++ module* 'std' and the Darwin master system header module
'Darwin'. Even attempting to use <assert.h>/<cassert> (as LLVM's test for
module support does) breaks like so:
While building module 'Darwin' imported from /usr/include/assert.h:42:
While building module 'std' imported from
[...]/llvm-git/build1/bin/../include/c++/v1/math.h:309:
In file included from <module-includes>:1:
In file included from
[...]/llvm-git/build1/bin/../include/c++/v1/algorithm:626:
In file included from [...]/llvm-git/build1/bin/../include/c++/v1/cstring:61:
[...]/llvm-git/build1/bin/../include/c++/v1/string.h:61:15: fatal error:
cyclic dependency in module 'Darwin': Darwin -> std -> Darwin
#include_next <string.h>
^
While building module 'Darwin' imported from /usr/include/assert.h:42:
In file included from <module-includes>:86:
In file included from
[...]/llvm-git/build1/bin/../lib/clang/3.8.0/include/tgmath.h:29:
[...]/llvm-git/build1/bin/../include/c++/v1/math.h:309:10: fatal error:
could not build module 'std'
#include <type_traits>
~~~~~~~~^
In file included from <stdin>:2:
/usr/include/assert.h:42:10: fatal error: could not build module 'Darwin'
#include <sys/cdefs.h>
~~~~~~~~^
3 errors generated.
I can't seem to get around this without turning off modules entirely--which is
a shame, because building LLVM is noticeably faster with modules on (at least,
when it works). No modification to libc++'s module map (at least, none that
I've tried) fixes this; the problem seems to be rooted in the fact that the
system headers are pulling in libc++'s "foo.h" wrappers.
* I'm talking, of course, about Clang's pre-compiled modules support, which is
turned on with -fmodules/-fcxx-modules.</pre>
</div>
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