MATLAB: Does the Shared Library Support Documentation in MATLAB 7.2 (R2006a) have references to nonexistent DLL files

MATLAB

There are references to nonexistent DLL files in the Shared Library Support Documentation in MATLAB 7.2 (R2006a) at the page located by entering the following at the MATLAB Command Prompt:

web([docroot,'/techdoc/ref/loadlibrary.html'])

This page references DLL files in Windows, but in this release, the DLL extension has been changed to be architecture-dependent.

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This is a bug in the documentation for R2006a. The documentation and example illustrating use of generic DLL support in MATLAB assume a shrlibsample.dll and shrlibsample.h file in the directory matlabroot\extern\examples\shrlib.

However, R2006a loads the following files in shrlib:

shrlibsample.c

shrlibsample.h

shrlibsample.mexw32.csf

shrlibsample.mexw32

shrhelp.h

yprime.c

yprime.h

yprime.mexw32.csf

yprime.mexw32

No explicit DLL files exist in the directory

The document web([docroot,'/techdoc/matlab_external/f42387.html']) also states "The .dll file for the shrlibsample library resides in the directory, extern\examples\shrlib."

The document should specify that depending on the platform, the extension of the dynamic library shrlibsample changes. So, the documentation should read:

"The library file for the shrlibsample library resides in the directory extern\examples\shrlib. MATLAB selects the appropriate version for your platform. The MEXEXT function returns the file extension that is used on your platform. See the MEX function for a list of all extensions used by MATLAB"

Related Solutions

MATLAB: How to call a DLL or Shared Library function using MEX-files instead of the Generic DLL / Shared Library Interface

This change has been incorporated into the documentation in Release 2009a (R2009a). For previous releases, read below for any additional information:

This is a basic example of calling one of the C Structure examples from the Generic DLL documentation using the MEX interface. Much of the work is doing the data conversion that is normally handled by the CALLLIB, LIBPOINTER, and LIBSTRUCT functions.

This example is configured for 32-bit MATLAB 7.4 (R2007a) and Microsoft Visual Studio 2005. Code will be similar but compiler options files will be different for other configurations. For example, the BAT-file will be a SH-file on Linux. The attached BAT-file is a modified version of the MSVC80OPTS.BAT file which is shipped with MATLAB in the following directory:

 <matlabroot>/bin/win32/mexopts

A similar file is available on other platforms in the following directory:

 <matlabroot>/bin

The C-code is platform independent, but it is compiled into a library which has different extensions depending on the platform, so the two MEX commands below will need to be modified based on the platform.

To execute this example, please download the attached C- and BAT-files to a working directory, and execute:

copyfile([matlabroot '\extern\examples\shrlib\shrlibsample.c']);
copyfile([matlabroot '\extern\examples\shrlib\shrlibsample.h']);
copyfile([matlabroot '\extern\examples\shrlib\shrhelp.h']);
mex -v -g -f msvc80buildlib.bat shrlibsample.c
mex -v -g myAddStructByRef.c shrlibsample.lib
struct.p1 = 4; struct.p2 = 7.3; struct.p3 = -290;
[res,st] = myAddStructByRef(struct)

This copies the Generic DLL example files to your working directory, builds the DLL with all relevant Exports files and import libraries (EXP- and LIB-files), then builds the MEX-file to call addStructByRef(). Finally, it calls the function on a test structure.

This will produce output similar to:

 C Struct:
   p1: 4.000000
   p2: 7
   p3: -290
 Calculated sum: -279.000000
 res = 
     p1: 5.5000
     p2: 1234
     p3: 12345678
 st =
   -279

This calls the same function used in the CALLLIB documentation:

addpath([matlabroot '\extern\examples\shrlib'])
loadlibrary shrlibsample shrlibsample.h
struct.p1 = 4; struct.p2 = 7.3; struct.p3 = -290; 
[res,st] = calllib('shrlibsample','addStructByRef',...
libstruct('c_struct',struct));

MATLAB: Do I get Library was not found Error while using external library in parpool

This error means that the library you are trying to call is not available in parallel workers.

Although, you have added required files to the parallel pool using 'AttachedFiles', the reason why this error is thrown is that those libraries are not loaded in parallel workers.

In order to have libraries available in those workers, please load libraries in each worker.

So, to fix this issue, please use loadlibrary to load libraries in each worker.

clear all;
addpath(fullfile(matlabroot,'extern','examples','shrlib'))
struct.p1 = 4; struct.p2 = 7.3; struct.p3 = -290;
parpool('AttachedFiles',{'shrlibsample.mexw64','shrlibsample.h','shrlibsample.c', 'shrhelp.h'}); 
parfor i=1:4
    if ~libisloaded('shrlibsample')
        loadlibrary('shrlibsample')
    end
[res,st] = calllib('shrlibsample','addStructByRef',struct);
end
unloadlibrary shrlibsample

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Related Solutions

MATLAB: How to call a DLL or Shared Library function using MEX-files instead of the Generic DLL / Shared Library Interface

MATLAB: Do I get Library was not found Error while using external library in parpool

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