Define MATLAB Function

Define the MATLAB function errorCheckExample in a separate file. This function calculates the square root of its input argument:

type errorCheckExample

function y = errorCheckExample(x)
y = sqrt(x);
end

Generate C Library and Executable

Generate a dynamically linked C library for errorCheckExample that accepts a double scalar input. Use a code configuration object with the RuntimeChecks parameter set to true. Also, use the -d option to name the code generation folder as codegen_c_dll.

cfg = coder.config('dll');
cfg.RuntimeChecks = true;
codegen -config cfg errorCheckExample -args 1 -d codegan_c_dll -report

Code generation successful: To view the report, open('codegan_c_dll/html/report.mldatx')

Open the code generation report and inspect the file errorCheckExample.c. The C function generated for your MATLAB function has the signature double errorCheckExample(double x). To calculate the square root, errorCheckExample invokes the sqrt library function which calculates only real square roots. So, errorCheckExample can accept only positive inputs. For negative inputs, errorCheckExample calls the generated utility function rtErrorWithMessageID that uses fprintf to write an error message to stderr and then uses abort to terminate the application.

static void rtErrorWithMessageID(const int b, const char *c,
                                 const char *aFcnName, int aLineNum)
{
  fprintf(stderr,
          "Domain error. To compute complex results from real x, use "
          "\'%.*s(complex(x))\'.",
          b, c);
  fprintf(stderr, "\n");
  fprintf(stderr, "Error in %s (line %d)", aFcnName, aLineNum);
  fprintf(stderr, "\n");
  fflush(stderr);
  abort();
}

When generating library code, the code generator also produces example main files main.h and main.c in the examples subfolder of the build folder. The supporting C files main_runtime_check.h and main_runtime_check.c are modified versions of these example files. The modified main function invokes errorCheckExample(-4), which produces a run-time error.

Run these commands to generate a C executable using the modified main files. Name the code generation folder codegen_c_exe. Name the executable file errorCheckExample_c by using the -o option with the codegen command.

cfg = coder.config('exe');
cfg.RuntimeChecks = true;
cfg.CustomSource = 'main_runtime_check.c';
cfg.CustomInclude = pwd;

codegen -config cfg main_runtime_check.c main_runtime_check.h errorCheckExample -args 1 -o errorCheckExample_c -d codegen_c_exe

Code generation successful.

Run the generated executable. Observe that it prints the error message that is hard-coded in the utility function rtErrorWithMessageID.

if isunix
    system('./errorCheckExample_c');
elseif ispc
    system('errorCheckExample_c.exe');
else
    disp('Platform is not supported');
end

Domain error. To compute complex results from real x, use 'sqrt(complex(x))'.
Error in sqrt (line 13)
./errorCheckExample_c: Aborted

Generate C++ Library and Executable

Generate a dynamically linked C++ library for errorCheckExample that accepts a scalar double input. Use a code configuration object with the RuntimeChecks parameter set to true. Also, use the -d option to name the code generation folder as codegen_cpp_dll.

cfg = coder.config('dll');
cfg.RuntimeChecks = true;
codegen -config cfg -lang:c++ errorCheckExample -args 1 -d codegen_cpp_dll -report

Code generation successful: To view the report, open('codegen_cpp_dll/html/report.mldatx')

Open the code generation report and inspect the file errorCheckExample.cpp. Similar to the C function generated in the previous section, errorCheckExample can accept only positive inputs. For negative inputs, errorCheckExample calls the utility function rtErrorWithMessageID. But in this case, the utility function throws a std:runtime_error exception that you can catch and handle in your hand-written main function.

static void rtErrorWithMessageID(const char *b, const char *aFcnName,
                                 int aLineNum)
{
  std::stringstream outStream;
  ((outStream << "Domain error. To compute complex results from real x, use \'")
   << b)
      << "(complex(x))\'.";
  outStream << "\n";
  ((((outStream << "Error in ") << aFcnName) << " (line ") << aLineNum) << ")";
  throw std::runtime_error(outStream.str());
}

When generating library code, the code generator also produces example main files main.h and main.c in the examples subfolder of the build folder. The supporting C++ files main_runtime_check.hpp and main_runtime_check.cpp are modified versions of these example files. The modified main() function invokes errorCheckExample(-4) inside a try-catch block. The block catches the exception and prints a modified message by prepending the string "Caught excaption: " to the message that the caught exception contains.

Run these commands to generate a C++ executable using the modified main files. Name the code generation folder codegen_cpp_exe. Name the executable file errorCheckExample_cpp.

cfg = coder.config('exe');
cfg.RuntimeChecks = true;
cfg.CustomSource = 'main_runtime_check.cpp';
cfg.CustomInclude = pwd;

codegen -config cfg -lang:c++ main_runtime_check.cpp main_runtime_check.hpp errorCheckExample -args 1 -o errorCheckExample_cpp -d codegen_cpp_exe

Code generation successful.

Run the generated executable. Observe that it prints the modified error message.

if isunix
    system('./errorCheckExample_cpp');
elseif ispc
    system('errorCheckExample_cpp.exe');
else
    disp('Platform is not supported');
end

Caught exception: Domain error. To compute complex results from real x, use 'sqrt(complex(x))'.
Error in sqrt (line 13)