<html>
    <head>
      <base href="http://llvm.org/bugs/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - Building clang with CMake outside LLVM tree without specifying CLANG_PATH_TO_LLVM_SOURCE"
   href="http://llvm.org/bugs/show_bug.cgi?id=17837">17837</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Building clang with CMake outside LLVM tree without specifying CLANG_PATH_TO_LLVM_SOURCE
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </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>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>jesper.eskilson@iar.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvmbugs@cs.uiuc.edu
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>I'm trying to build Clang using CMake, and I want to keep the Clang and LLVM
source trees separate. Looking at the Clang top-level CMakeLists.txt it should
be possible, but when I try to build with 

cmake ... -DCLANG_PATH_TO_LLVM_BUILD=/my/llvm ...

the build fails with 

FAILED: cd
/home/jesperes/dev/wtd-analyzer/build/clang-prefix/src/clang-build/include/clang/Driver
&& /home/jesperes/dev/wtd-analyzer/build/llvm-prefix/bin/llvm-tblgen
-gen-opt-parser-defs -I
/home/jesperes/dev/wtd-analyzer/build/clang-prefix/src/clang/include/clang/Driver
-I /lib/Target -I /include
/home/jesperes/dev/wtd-analyzer/build/clang-prefix/src/clang/include/clang/Driver/Options.td
-o
/home/jesperes/dev/wtd-analyzer/build/clang-prefix/src/clang-build/include/clang/Driver/Options.inc.tmp
/home/jesperes/dev/wtd-analyzer/build/clang-prefix/src/clang/include/clang/Driver/Options.td:15:9:
error: Could not find include file 'llvm/Option/OptParser.td'
include "llvm/Option/OptParser.td"
        ^

I noted the "-I /lib/Target", which got me suspicious and started poking around
in the CMakeLists.txt file, and discovered this line:

set(LLVM_MAIN_INCLUDE_DIR "${LLVM_MAIN_SRC_DIR}/include")

but LLVM_MAIN_SRC_DIR is only set if CLANG_PATH_TO_LLVM_SOURCE is set. However,
the documentation of CLANG_PATH_TO_LLVM_SOURCE claims that it is not necessary
to set if building against an installed LLVM.

It looks like the proper solution is to set LLVM_MAIN_INCLUDE_DIR properly
using output from "llvm-config --includedir` if CLANG_PATH_TO_LLVM_SOURCE is
not set.</pre>
        </div>
      </p>
      <hr>
      <span>You are receiving this mail because:</span>
      
      <ul>
          <li>You are on the CC list for the bug.</li>
      </ul>
    </body>
</html>