MATLAB Codegen Compiler Error

Hi,

I am using attempting to convert MATLAB code to c using codegen. This works fine when I convert to mex directly. However, when I 1) use codegen to generate c files then 2) attempt to generate a mex file from the c files (using the mex command), I get the following error:

"Error using mex Undefined symbols for architecture x86_64:

[several dozen reference errors]

ld: symbol(s) not found for architecture x86_64

clang: error: linker command failed with exit code 1 (use -v to see invocation)"

Is there a reason why this would work directly from the codegen command but fail when I attempt to do it step-wise? I am on a mac running High Sierra 10.13.3 with MATLAB 2017b.

Thanks for the help.

Update: Here is an example using the standard MATLAB interp1 function.

n = 130;
x = linspace(0,50,n)';
y = x.^2;
query = 27.5;
codegen interp1 -args {x,y,query}

If, instead of using interp1_mex, I attempt to use the generated c file directly, I get an error. The command

mex interp1.c

returns the error

Error using mex
Undefined symbols for architecture x86_64:
  "_b_error", referenced from:
      _interp1 in interp1.o
  "_error", referenced from:
      _interp1 in interp1.o
  "_mexFunction", referenced from:
     -exported_symbol[s_list] command line option
  "_muDoubleScalarIsNaN", referenced from:
      _interp1 in interp1.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

[Walter Roberson]

That sounds as if some library was not linked into the executable.

[Ryan Livingston]

Can you explain your workflow a bit more? Some command snippets would be useful showing how you're using codegen and calling mex

[Lawrence Costa]

Sorry for the delay. Added an example of the issue in the question body.

[Walter Roberson]

When you use mex without any options, it expects that the source you list is a function written to mex standards, for the purpose of calling the code directly from MATLAB. To compile stand-alone code for use outside of MATLAB you need to either compile outside of the mex toolchain, or else use some of the options to mex, such as -client

Answer 1

[Raghu Boggavarapu]

Write a new MATLAB function using coder.cinclude and coder.ceval to call the generated c function. User coder.updateBuildInfo to link the autogenerated library and also to reference the generated code directory for include paths. Now use MATLAB Coder to generate MEX for this newly written function.