How to use external C library in Codegen process to generate mex file

I'm trying to use the CSparse/CXSParse toolbox in a Matlab coder project.

Here is a sample code i want to compile. C (only) code is generated, but linking fails, so i cannot get mex files from it or test the generated code in matlab.

Here is my command : codegen -config:mex testCSparse

The function :

    function [OUT] = testCSparse %# codegen
    %This function generate C code to test input et output 
    %   variable types uses by CSparse Library

    v1 = round(rand(10,1)*100);
    v2 = round(rand(10,1)*100);
    v3 = 1:10;

    if coder.target('MATLAB') % for matlab 2014
        OUT = cs_sparse(v1,v2,v3); % here a mexed C func is called 
    else
        OUT = struct;
        OUT = coder.ceval('cs_sparse',v1,v2,v3);

    % how to use this struct OUT in matlab : newMat = OUT generates an error..

    end

It leads to an error. The codegen command allows me "Generate code only" without errors, if i select a mex output it doesn't work. So i cannot test it on Matlab.

---------------- Error Generated :

Build Log 1 xcrun -sdk macosx10.10 clang -c -fno-common -arch x86_64 -isysroot [•••]

 -I "/Applications/MATLAB_R2014a.app/extern/include" -I "." "testCSparse.c"
    5   testCSparse.c:43:3: warning: implicit declaration of
    6         function 'cs_sparse' is invalid in C99
    7         [-Wimplicit-function-declaration]
    8     cs_sparse(v1, v2, dv0);
    9     ^
   10   1 warning generated.
   11   xcrun  -sdk macosx10.10  clang -c -fno-common -arch x86_64 -isysroot 
   14   xcrun  -sdk macosx10.10  clang -Wl,-exported_symbols_list,testCSparse_mex_mex.map -arch x86_64 -Wl,-syslibroot,/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk -mmacosx-version-min=10.10 -bundle  -O -o testCSparse_mex.mexmaci64  testCSparse_data.o testCSparse_initialize.o testCSparse_terminate.o testCSparse.o _coder_testCSparse_api.o _coder_testCSparse_mex.o _coder_testCSparse_info.o  -L/Applications/MATLAB_R2014a.app/bin/maci64 -lmx -lmex -lmat -lstdc++ -lemlrt -lcovrt -lut -lmwmathutil -lmwblas 
   15   Undefined symbols for architecture x86_64:
   16     "_cs_sparse", referenced from:
   17         _testCSparse in testCSparse.o
   18   ld: symbol(s) not found for architecture x86_64
   19   clang: error: linker command failed with exit code 1 (use -v to see invocation)
   20   gmake: *** [testCSparse_mex.mexmaci64] Error 1

Answer 1

[Raghu Boggavarapu]

You also need to include the header file that declares cs_sparse function using coder.cinclude and link the library that defines it using coder.updateBuildInfo to avoid build failure.