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<h2 class="title" style="clear: both"><a id="build_unix_notes"></a>Architecture independent FAQ</h2>
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<ol type="1">
<li>
<span class="bold">
<strong>I have gcc installed, but configure
fails to find it.</strong>
</span>
<p>
Berkeley DB defaults to using the native C compiler
if none is specified. That is usually "cc", but some
platforms require a different compiler to build
multithreaded code. To configure Berkeley DB to build
with gcc, run configure as follows:
</p>
<pre class="programlisting">env CC=gcc ../dist/configure ...</pre>
</li>
<li>
<span class="bold">
<strong>When compiling with gcc, I get
unreferenced symbols; for example the following:
<pre class="programlisting">symbol __muldi3: referenced symbol not found
symbol __cmpdi2: referenced symbol not found</pre></strong>
</span>
<p>
Berkeley DB often uses 64-bit integral types on
systems supporting large files, and gcc performs
operations on those types by calling library
functions. These unreferenced symbol errors are
usually caused by linking an application by calling
"ld" rather than by calling "gcc": gcc will link in
libgcc.a and will resolve the symbols. If that does
not help, another possible workaround is to
reconfigure Berkeley DB using the <a class="link" href="build_unix_conf.html#build_unix_conf.--disable-largefile">--disable-largefile</a>
configuration option and then rebuild.
</p>
</li>
<li>
<span class="bold">
<strong>My C++ program traps during a
failure in a DB call on my gcc-based
system.</strong>
</span>
<p>
We believe there are some severe bugs in the
implementation of exceptions for some gcc compilers.
Exceptions require some interaction between compiler,
assembler, and runtime libraries. We're not sure
exactly what is at fault, but one failing combination
is gcc 2.7.2.3 running on SuSE Linux 6.0. The problem
on this system can be seen with a rather simple test
case of an exception thrown from a shared library and
caught in the main program.
</p>
<p>
A variation of this problem seems to occur on AIX,
although we believe it does not necessarily involve
shared libraries on that platform.
</p>
<p>
If you see a trap that occurs when an exception
might be thrown by the Berkeley DB runtime, we suggest
that you use static libraries instead of shared
libraries. See the documentation for configuration. If
this doesn't work and you have a choice of compilers,
try using a more recent gcc- or a non-gcc based
compiler to build Berkeley DB.
</p>
<p>
Finally, you can disable the use of exceptions in
the C++ runtime for Berkeley DB by using the
<a href="../api_reference/CXX/envcreate.html#env_DB_CXX_NO_EXCEPTIONS" class="olink">DB_CXX_NO_EXCEPTIONS</a> flag with the <a href="../api_reference/CXX/env.html" class="olink">DbEnv</a>
or <a href="../api_reference/CXX/db.html" class="olink">Db</a> constructors. When this flag is on,
all C++ methods fail by returning an error code rather
than throwing an exception.
</p>
</li>
<li>
<span class="bold">
<strong>I get unexpected results and
database corruption when running threaded
programs.</strong>
</span>
<p>
<span class="bold"><strong>I get error messages that mutex
(for example, pthread_mutex_XXX or mutex_XXX)
functions are undefined when linking applications
with Berkeley DB.</strong></span>
</p>
<p>
On some architectures, the Berkeley DB library uses
the ISO POSIX standard pthreads and UNIX International
(UI) threads interfaces for underlying mutex support;
for example, Solaris and HP-UX. You can specify compilers or
compiler flags, or link with the appropriate thread
library when loading your application to resolve the
undefined references:
</p>
<pre class="programlisting">cc ... -lpthread ...
cc ... -lthread ...
xlc_r ...
cc ... -mt ...</pre>
<p>
See the appropriate architecture-specific Reference
Guide pages for more information.
</p>
<p>
On systems where more than one type of mutex is
available, it may be necessary for applications to use
the same threads package from which Berkeley DB draws
its mutexes. For example, if Berkeley DB was built to
use the POSIX pthreads mutex calls for mutex support,
the application may need to be written to use the
POSIX pthreads interfaces for its threading model.
This is only conjecture at this time, and although we
know of no systems that actually have this
requirement, it's not unlikely that some exist.
</p>
<p>
In a few cases, Berkeley DB can be configured to
use specific underlying mutex interfaces. You can use
the <a class="link" href="build_unix_conf.html#build_unix_conf.--enable-posixmutexes">
--enable-posixmutexes</a> and <a class="link" href="build_unix_conf.html#build_unix_conf.--enable-uimutexes">--enable-uimutexes</a>
configuration options to specify the POSIX and Unix International (UI)
threads packages. This should not, however, be
necessary in most cases.
</p>
<p>
In some cases, it is vitally important to make sure
that you load the correct library. For example, on
Solaris systems, there are POSIX pthread interfaces in
the C library, so applications can link Berkeley DB
using only C library and not see any undefined
symbols. However, the C library POSIX pthread mutex
support is insufficient for Berkeley DB, and Berkeley
DB cannot detect that fact. Similar errors can arise
when applications (for example, tclsh) use dlopen to
dynamically load Berkeley DB as a library.
</p>
<p>
If you are seeing problems in this area after you
confirm that you're linking with the correct
libraries, there are two other things you can try.
First, if your platform supports interlibrary
dependencies, we recommend that you change the
Berkeley DB Makefile to specify the appropriate
threads library when creating the Berkeley DB shared
library, as an interlibrary dependency. Second, if
your application is using dlopen to dynamically load
Berkeley DB, specify the appropriate thread library on
the link line when you load the application itself.
</p>
</li>
<li>
<span class="bold">
<strong>I get core dumps when running
programs that fork children.</strong>
</span>
<p>
Berkeley DB handles should not be shared across
process forks, each forked child should acquire its
own Berkeley DB handles.
</p>
</li>
<li>
<span class="bold">
<strong>I get reports of uninitialized
memory reads and writes when running software analysis
tools (for example, Rational Software Corp.'s Purify
tool).</strong>
</span>
<p>
For performance reasons, Berkeley DB does not write
the unused portions of database pages or fill in
unused structure fields. To turn off these errors when
running software analysis tools, build with the <a class="link" href="build_unix_conf.html#build_unix_conf.--enable-umrw">--enable-umrw</a>
configuration option.
</p>
</li>
<li>
<span class="bold">
<strong>Berkeley DB programs or the test
suite fail unexpectedly.</strong>
</span>
<p>
The Berkeley DB architecture does not support
placing the shared memory regions on remote
filesystems -- for example, the Network File System
(NFS) or the Andrew File System (AFS). For this
reason, the shared memory regions (normally located in
the database home directory) must reside on a local
filesystem. See <a href="../programmer_reference/env_region.html" class="olink">Shared memory region</a> for more information.
</p>
<p>
With respect to running the test suite, always
check to make sure that TESTDIR is not on a remote
mounted filesystem.
</p>
</li>
<li>
<span class="bold">
<strong>The <a href="../api_reference/C/db_dump.html" class="olink">db_dump</a> utility fails to build.</strong>
</span>
<p>
The <a href="../api_reference/C/db_dump.html" class="olink">db_dump185</a> utility is the utility that supports the
conversion of Berkeley DB 1.85 and earlier databases
to current database formats. If the build errors look
something like the following, it means the db.h
include file being loaded is not a Berkeley DB 1.85
version include file:
</p>
<pre class="programlisting">db_dump185.c: In function `main':
db_dump185.c:210: warning: assignment makes pointer from integer
without a cast
db_dump185.c:212: warning: assignment makes pointer from integer
without a cast
db_dump185.c:227: structure has no member named `seq'
db_dump185.c:227: `R_NEXT' undeclared (first use in this function)</pre>
<p>
If the build errors look something like the
following, it means that the Berkeley DB 1.85 code was
not found in the standard libraries:
</p>
<pre class="programlisting">cc -o db_dump185 db_dump185.o
ld:
Unresolved:
dbopen</pre>
<p>
To build the <a href="../api_reference/C/db_dump.html" class="olink">db_dump185</a> utility, the Berkeley DB version
1.85 code must already been built and available on the
system. If the Berkeley DB 1.85 header file is not
found in a standard place, or if the library is not
part of the standard libraries used for loading, you
will need to edit your Makefile, and change the
following lines:
</p>
<pre class="programlisting">DB185INC=
DB185LIB=</pre>
<p>
So that the system Berkeley DB 1.85 header file and
library are found; for example:
</p>
<pre class="programlisting">DB185INC=/usr/local/include
DB185LIB=-ldb185</pre>
</li>
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