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<h2 class="title" style="clear: both"><a id="build_unix_qnx"></a>QNX</h2>
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<ol type="1">
<li>
<span class="bold">
<strong>To what versions of QNX has DB been ported?</strong>
</span>
<p>
Berkeley DB has been ported to the QNX Neutrino
technology which is commonly referred to as QNX RTP
(Real-Time Platform). Berkeley DB has not been ported
to earlier versions of QNX, such as QNX 4.25.
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</li>
<li>
<span class="bold">
<strong>Building Berkeley DB shared
libraries fails.</strong>
</span>
<p>
The <code class="filename">/bin/sh</code> utility
distributed with some QNX releases drops core when
running the GNU libtool script (which is used to build
Berkeley DB shared libraries). There are two
workarounds for this problem: First, only build static
libraries. You can disable building shared libraries
by specifying the configuration flag when configuring
Berkeley DB.
</p>
<p>
Second, build Berkeley DB using an alternate shell.
QNX distributions include an accessories disk with
additional tools. One of the included tools is the GNU
bash shell, which is able to run the libtool script.
To build Berkeley DB using an alternate shell, move
<code class="filename">/bin/sh</code> aside, link or copy
the alternate shell into that location, configure,
build and install Berkeley DB, and then replace the
original shell utility.
</p>
</li>
<li>
<span class="bold">
<strong>Are there any QNX filesystem
issues?</strong>
</span>
<p>
Berkeley DB generates temporary files for use in
transactionally protected file system operations. Due
to the filename length limit of 48 characters in the
QNX filesystem, applications that are using
transactions should specify a database name that is at
most 43 characters.
</p>
</li>
<li>
<span class="bold">
<strong>What are the implications of QNX's
requirement to use <code class="literal">shm_open</code>(2) in
order to use <code class="literal">mmap</code>(2)?</strong>
</span>
<p>
QNX requires that files mapped with
<code class="literal">mmap</code>(2) be opened using
<code class="literal">shm_open</code>(2). There are other
places in addition to the environment shared memory
regions, where Berkeley DB tries to memory map files
if it can.
</p>
<p>
The memory pool subsystem normally attempts to use
<code class="literal">mmap</code>(2) even when using private
memory, as indicated by the <a href="../api_reference/C/envopen.html#envopen_DB_PRIVATE" class="olink">DB_PRIVATE</a> flag to
<a href="../api_reference/C/envopen.html" class="olink">DB_ENV->open()</a>. In the case of QNX, if an application is
using private memory, Berkeley DB will not attempt to
map the memory and will instead use the local cache.
</p>
</li>
<li>
<span class="bold">
<strong>What are the implications of QNX's
mutex implementation using microkernel
resources?</strong>
</span>
<p>
On QNX, the primitives implementing mutexes consume
system resources. Therefore, if an application
unexpectedly fails, those resources could leak.
Berkeley DB solves this problem by always allocating
mutexes in the persistent shared memory regions. Then,
if an application fails, running recovery or
explicitly removing the database environment by
calling the <a href="../api_reference/C/envremove.html" class="olink">DB_ENV->remove()</a> method will allow Berkeley DB
to release those previously held mutex resources. If
an application specifies the <a href="../api_reference/C/envopen.html#envopen_DB_PRIVATE" class="olink">DB_PRIVATE</a> flag
(choosing not to use persistent shared memory), and
then fails, mutexes allocated in that private memory
may leak their underlying system resources. Therefore,
the <a href="../api_reference/C/envopen.html#envopen_DB_PRIVATE" class="olink">DB_PRIVATE</a> flag should be used with caution on
QNX.
</p>
</li>
<li>
<span class="bold">
<strong>The make clean command fails to
execute when building the Berkeley DB SQL
interface.</strong>
</span>
<p>
Remove the build directory manually to clean up and
proceed.
</p>
</li>
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