View source for Documentation/4.5/Developers/FAQ/Building

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== How is organized the Slicer build tree ? ==

The Slicer build tree has two levels:
* <code>~/Projects/Slicer-SuperBuild</code>
* <code>~/Projects/Slicer-SuperBuild/Slicer-build</code>

The first level ''manages'' all the external dependencies of Slicer (VTK, ITK, Python, ...). The second level is the "traditional" build directory of Slicer.

See [[Documentation/{{documentation/version}}/Developers/DirectoryStructure|Slicer directory structure]]

== What is a clean build ? ==

Doing a ''clean build'' means that 

(1) all directories and files in the top-level build directory <code>~/Projects/Slicer-SuperBuild</code> are removed.

and 

(2) you updated your source checkout and have no locally modified files.

== What to do if QtSDK installer hangs ? ==

If QtSDK installer hangs, use <code>-style cleanlooks</code> command line option. For details, see [http://http://qt-project.org/forums/viewthread/17040/#85212 here].

== Which minimum version of GLIBC is needed to build Slicer ? ==

The minimum version of GLIBC required to build Slicer is defined by the minimum version required by the pre-compiler binaries used when building Slicer. In our case, a small pre-compiled executable called the [http://www.commontk.org/index.php/Tools:_Application_launcher#What_is_CTK_Application_Launcher_.3F CTK AppLauncher] is [https://github.com/Slicer/Slicer/blob/master/SuperBuild/External_CTKAPPLAUNCHER.cmake downloaded] and used at configure and build time each time python has to be invoked.

The precompiled CTKAppLauncher imposes the following requirements regarding GLIBC and GLIBCXX libraries installed on your system:

<pre>
$ strings CTKAppLauncher | ack GLIBC
GLIBC_2.2.5
GLIBCXX_3.4.11
GLIBCXX_3.4.9
GLIBCXX_3.4
GLIBC_2.3.3
GLIBC_2.3.2
GLIBC_2.4
GLIBC_2.3
</pre>


To check that your system provides the required GLIBCXX and GLIB versions, you could run the following command and check that the requirement of the launcher can be satisfied:

<pre>
$ strings /usr/lib/libstdc++.so.6 | grep GLIBCXX
GLIBCXX_3.4
GLIBCXX_3.4.1
GLIBCXX_3.4.2
GLIBCXX_3.4.3
GLIBCXX_3.4.4
GLIBCXX_3.4.5
GLIBCXX_3.4.6
GLIBCXX_3.4.7
GLIBCXX_3.4.8
GLIBCXX_3.4.9
GLIBCXX_3.4.10
GLIBCXX_3.4.11
GLIBCXX_3.4.12
GLIBCXX_3.4.13
GLIBCXX_3.4.14
GLIBCXX_3.4.15
GLIBCXX_3.4.16
GLIBCXX_3.4.17
</pre>

<pre>
$ strings /lib/libc.so.6 | grep GLIBC
GLIBC_2.2.5
GLIBC_2.2.6
GLIBC_2.3
GLIBC_2.3.2
GLIBC_2.3.3
GLIBC_2.3.4
GLIBC_2.4
GLIBC_2.5
GLIBC_2.6
GLIBC_2.7
GLIBC_2.8
GLIBC_2.9
GLIBC_2.10
GLIBC_2.11
</pre>

== What to do if Visual Studio compiler crashes ? ==

If the compiler crashes on Windows saying "Microsoft C/C++ Compiler Driver has stopped working", then it's most probably due to long build folder paths. To fix this the Slicer build directory should be moved and/or renamed. A typical build folder path is C:\S4D

== How to build Slicer with SSL support ? ==

To build Slicer with SSL support, you need to build (or download) Qt with SSL support and configure Slicer with <code>-DSlicer_USE_PYTHONQT_WITH_OPENSSL:BOOL=ON</code>