MATLAB: Does engOpen return before MATLAB is finished initializing when MATLAB calls a system command on startup

concurrencydosengineMATLABmatlabrcstartupsystem

Why does engOpen return before MATLAB is finished initializing when MATLAB calls a system command on startup?

As part of my matlabrc.m or startup.m, MATLAB makes a call to a system command via the DOS, UNIX, or SYSTEM functions. My call to engOpen returns before that command is done processing therefore its return values are not initialized in the MATLAB workspace.

This behavior is limited to calls to DOS or SYSTEM that MATLAB performs on startup.

Best Answer

This enhancement has been incorporated in Release 14 Service Pack 3 (R14SP3). For previous product releases, read below for any possible workarounds:

This has been verified as a bug in MATLAB 6.5 (R13) in the way that the MATLAB Engine evaluates calls to system functions. As a workaround, set a flag after the system call has terminated and test that before proceeding with your MATLAB Engine application.

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MATLAB: What is the output from VER when called from a standalone application on a computer that does not have MATLAB installed

This bug has been fixed in Release 2007b (R2007b). For previous product releases, read below for any possible workarounds:

Calling VER from a compiled application without an output argument will display information similar to calling VER from the command prompt in MATLAB. The MATLAB Version will coincide with the version of MATLAB that the MCR is from and the operating system will be the operating system of the machine running the application. For example, on a Windows XP machine it would look like the following:

 ------------------------------------------------------------------------------------- 
 MATLAB Version 7.0.4.365 (R14) Service Pack 2 
 MATLAB License Number: unknown 
 Operating System: Microsoft Windows XP Version 5.1 (Build 2600: Service Pack 2) 
 Java VM Version: Java 1.5.0 with Sun Microsystems Inc. Java HotSpot(TM) Client VM 
 -------------------------------------------------------------------------------------

However, calling the functional form of VER, where the output is saved to a structure, will not return the same response in a stand-alone application on a machine that does not have MATLAB installed. To work around this issue, you may be able to use the string returned by the VERSION command in place of the VER structure. For example, on the same machine as previously described, the command:

a=version;

returns the string

 a =
 7.0.4.365 (R14) Service Pack 2

in MATLAB and in a stand-alone application.

MATLAB: EngOpen hangs up when calling from dll

The problem was calling engOpen while loading the library or creating a COM thread in the DllMain. This goes against the best practices suggested here - https://docs.microsoft.com/en-us/windows/win32/dlls/dynamic-link-library-best-practices. I called engOpen from a method that wasn't statically initialized using GetProcAddress and it worked fine.

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Related Solutions

MATLAB: What is the output from VER when called from a standalone application on a computer that does not have MATLAB installed

MATLAB: EngOpen hangs up when calling from dll

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