Mex Link Failure: Undefined Symbols for Architecture

Hi, I run Matlab 2016b on Mac 10.12.3, compiling with Xcode 7.3.1. I'm trying to make a model with IQMmakeMEXmodel but when I run it, it states:

Error using mex
Undefined symbols for architecture x86_64:
  "_CVODEmex25", referenced from:
      _mexFunction in MEXmodel.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Error in mexcompileIQM (line 21)
eval(sprintf('mex -O -I''%s'' %s.c ''%s'';',includefolder,filename,libpath));

Error in IQMmakeMEXmodel (line 341)
    mexcompileIQM(MEXfunctionName);

Any idees how to solve this one?

Answer 1

[Saurabh]

Hi @Adriano Martinelli,

I understand that there was an issue during the linking process when tried to compile a MEX file using MATLAB’s ‘mex’ command on Mac system.

The error message encountered here:

Error using mex
Undefined symbols for architecture x86_64:
"_CVODEmex25", referenced from:
_mexFunction in MEXmodel.o

indicates that the linker cannot find the symbol ‘_CVODEmex25’ during the compilation of MEX file. This typically occurs when the required library containing this symbol is not linked correctly.

Potential Causes and Solutions:

1. Missing or Incorrect Library Linking

The symbol '_CVODEmex25' suggests that code depends on the CVODE library from the SUNDIALS suite. If this library is not linked correctly, this error will be encountered.

Solution:

• Ensure the library is installed: Verify that the CVODE library is installed on the system.
• Link the library during compilation: When compiling the MEX file, you need to link against the CVODE library. This can be done by adding the '-lcvode' flag to 'mex' command, and specifying the library path with -L. For example:

mex -I/path/to/include -L/path/to/lib -lcvode MEXmodel.c

• Replace /path/to/include and /path/to/lib with the actual paths to the CVODE headers and library files.

2. Incompatible Architecture Between MATLAB and Libraries:

• If there's a mismatch between the architecture of MATLAB and the compiled libraries (e.g., MATLAB is 64-bit, but the library is 32-bit), this error will be encountered.

Solution:

• Check MATLAB's architecture: In MATLAB, run:

mexext

• This will return something like mexa64, indicating a 64-bit architecture.
• Check library architecture: In the terminal, run:

file /path/to/libcvode.dylib

• Ensure it matches MATLAB's architecture.
• Recompile the library if necessary: If there's a mismatch, recompile the CVODE library to match MATLAB's architecture.

3. Incorrect mex Configuration

• MATLAB uses a configuration file to determine how to compile MEX files. If this configuration is incorrect, it can lead to linking errors.

Solution:

• Run mex -setup: In MATLAB, execute:

mex -setup

• This will guide through selecting the appropriate compiler. Ensure that the selected compiler is compatible with system and MATLAB version.

4. Missing mexFunction Definition

• Every MEX file must define a 'mexFunction', which serves as the entry point. If this function is missing, you'll encounter linking errors.

Solution:

• Check source code: Ensure that 'MEXmodel.c' file contains the following function:

void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) {
    // code here
}

• If this function is missing, add it to the source code.

I hope this helps!