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Support for dynamic loading.

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Andrew Johnson
2009-02-27 23:38:33 +00:00
parent 9e07d56548
commit 3a6deaa60a
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documentation/RELEASE_NOTES.html
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<h2 align="center">Changes between 3.14.10 and 3.14.11</h2>
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<h4>Support for dynamic loading</h4>
<p>The existing OSI epicsFindSymbol API has been expanded to support dynamic
loading of binary files, on architectures where the facilities necessary to
implement this are provided (currently Linux, Solaris, Darwin and vxWorks). A
new but optional command is provided for iocsh which calls the new
<tt>epicsLoadLibrary()</tt> function. In order to include this command in an
IOC, you must include the <tt>dlload.dbd</tt> file; the command will then be
installed when the IOC's <tt>ioc_registerRecordDeviceDriver</tt> routine is
run.</p>
<p>To dynamically load a new routine for use with the sub or aSub record types,
you also have to register the subroutines at runtime. You can use the EPICS
build system and the registerRecordDeviceDriver.pl script to write the necessary
code for you, you just have to create a .dbd file that declares the functions in
the library and add the derived .cpp file to the library sources. The product of
your build should be a <tt>LOADABLE_LIBRARY</tt> to ensure that the correct
linker commands are used.</p>
<p>After a shared library is loaded into the IOC using the new iocsh
<tt>dlload</tt> command you will usually have to run the
<tt>lib_registerRecordDeviceDriver</tt> routine to register the components that
were mentioned in the .dbd file. After registration the functions can be found
as normal by setting the SNAM field of your sub or aSub record instances. Once
loaded, shared libraries cannot be unloaded again as there is no way to be sure
that some other part of the IOC doesn't still have a pointer to something inside
the module.</p>
<p>Components provided by a shared library can include functions for sub and
aSub records, iocsh commands, time providers and sequence programs. Record and
device support code may be possible, but there are complications in creating the
.dbd file so we don't recommend it yet. It is possible to load libraries after
iocInit, but the code is not re-entrant so should only be used from the main
thread. Adding new record types or device support will not work after
iocInit.</p>
<h4>Perl5 CA library</h4>
<p>The <tt>CA::put</tt> and <tt>CA::put_callback</tt> methods now use the native