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Configure Language Standard for Target System

Open Script

Specify standard library extensions that the code generator uses for math operations. When you generate code for a new model or with a new configuration set object, the code generator uses the ISO®/IEC 9899:1999 C (C99 (ISO)) library by default. For preexisting models and configuration set objects, the code generator uses the library specified by the Language standard parameter.

If your compiler supports the ISO®/IEC 9899:1990 (C89/C90 (ANSI)), ISO/IEC 14882:2003(C++03 (ISO) or ISO/IEC 14882:2011(C++11 (ISO)) math library extensions, you can change the language standard setting. The C++03 (ISO) or C++11 (ISO) library is an option when you select C++ for the programming language.

The C99 library leverages the performance that a compiler offers over standard ANSI C. When using the C99 library, the code generator produces calls to ISO C functions when possible. For example, the generated code calls the function sqrtf(), which operates on single-precision data, instead of sqrt().

To change the library setting, use the Configuration Parameters > Code Generation > Language standard parameter. The command-line equivalent is TargetLangStandard.

Generate and Inspect ANSI C Code

1. Open the example model CStandardMathLib.

2. Generate code.

### Starting build procedure for: CStandardMathLib
### Successful completion of code generation for: CStandardMathLib

Build Summary

Top model targets:

Model             Build Reason                                         Status           Build Duration
======================================================================================================
CStandardMathLib  Information cache folder or artifacts were missing.  Code generated.  0h 0m 10.635s 

1 of 1 models built (0 models already up to date)
Build duration: 0h 0m 11.566s

3. Examine the code in the generated file CStandardMathLib.c. Note that the code calls the sqrt function.

  if (rtb_Abs2 < 0.0F) {
    rtb_Abs2 = -(real32_T)sqrt((real32_T)fabs(rtb_Abs2));
  } else {
    rtb_Abs2 = (real32_T)sqrt(rtb_Abs2);
  }

  /* Gain: '<Root>/Gain1' incorporates:
   *  Constant: '<Root>/Constant'
   *  Sqrt: '<Root>/get_hypot1'
   *  Sum: '<Root>/Sum'
   *
   * About '<Root>/get_hypot1':
   *  Operator: signedSqrt
   */
  rtb_Abs2 = (rtb_Abs2 - 1.0F) * 343.0F;

  /* Rounding: '<Root>/fix1' */
  if (rtb_Abs2 < 0.0F) {
    /* Outport: '<Root>/Out1' */
    CStandardMathLib_Y.Out1 = (real32_T)ceil(rtb_Abs2);
  } else {
    /* Outport: '<Root>/Out1' */
    CStandardMathLib_Y.Out1 = (real32_T)floor(rtb_Abs2);
  }

  /* End of Rounding: '<Root>/fix1' */

  /* Abs: '<Root>/Abs2' incorporates:
   *  Inport: '<Root>/In2'
   */
  rtb_Abs2 = (real32_T)fabs(CStandardMathLib_U.In2);

  /* Outport: '<Root>/Out2' incorporates:
   *  Constant: '<Root>/Constant1'
   *  Gain: '<Root>/Gain2'
   *  Math: '<Root>/get_hypot2'
   *  Rounding: '<Root>/fix2'
   *  Sum: '<Root>/Sum2'
   *  Trigonometry: '<S1>/cos'
   *  Trigonometry: '<S1>/sin'
   */
  CStandardMathLib_Y.Out2 = (real32_T)floor((rt_hypotf_snf((real32_T)sin
    (rtb_Abs2), (real32_T)cos(rtb_Abs2)) - 1.0F) * 343.0F);
}

/* Model initialize function */
void CStandardMathLib_initialize(void)
{
  /* Registration code */

  /* initialize non-finites */
  rt_InitInfAndNaN(sizeof(real_T));

  /* initialize error status */
  rtmSetErrorStatus(CStandardMathLib_M, (NULL));

  /* external inputs */
  (void)memset(&CStandardMathLib_U, 0, sizeof(ExtU_CStandardMathLib_T));

  /* external outputs */
  (void)memset(&CStandardMathLib_Y, 0, sizeof(ExtY_CStandardMathLib_T));
}

/* Model terminate function */
void CStandardMathLib_terminate(void)
{
  /* (no terminate code required) */
}

Generate and Inspect ISO C Code

1. Change the setting of Language standard to C99 (ISO). Alternatively, at the command line, set TargetLangStandard to C99 (ISO).

2. Regenerate the code.

### Starting build procedure for: CStandardMathLib
### Successful completion of code generation for: CStandardMathLib

Build Summary

Top model targets:

Model             Build Reason                                         Status           Build Duration
======================================================================================================
CStandardMathLib  Information cache folder or artifacts were missing.  Code generated.  0h 0m 11.033s 

1 of 1 models built (0 models already up to date)
Build duration: 0h 0m 11.843s

3. Reexamine the code in the generated file CStandardMathLib.c. Now the generated code calls the function sqrtf instead of sqrt.

  if (rtb_Abs2 < 0.0F) {
    rtb_Abs2 = -sqrtf(fabsf(rtb_Abs2));
  } else {
    rtb_Abs2 = sqrtf(rtb_Abs2);
  }

  /* Outport: '<Root>/Out1' incorporates:
   *  Constant: '<Root>/Constant'
   *  Gain: '<Root>/Gain1'
   *  Rounding: '<Root>/fix1'
   *  Sqrt: '<Root>/get_hypot1'
   *  Sum: '<Root>/Sum'
   *
   * About '<Root>/get_hypot1':
   *  Operator: signedSqrt
   */
  CStandardMathLib_Y.Out1 = truncf((rtb_Abs2 - 1.0F) * 343.0F);

  /* Abs: '<Root>/Abs2' incorporates:
   *  Inport: '<Root>/In2'
   */
  rtb_Abs2 = fabsf(CStandardMathLib_U.In2);

  /* Outport: '<Root>/Out2' incorporates:
   *  Constant: '<Root>/Constant1'
   *  Gain: '<Root>/Gain2'
   *  Math: '<Root>/get_hypot2'
   *  Rounding: '<Root>/fix2'
   *  Sum: '<Root>/Sum2'
   *  Trigonometry: '<S1>/cos'
   *  Trigonometry: '<S1>/sin'
   */
  CStandardMathLib_Y.Out2 = floorf((rt_hypotf_snf(sinf(rtb_Abs2), cosf(rtb_Abs2))
    - 1.0F) * 343.0F);
}

/* Model initialize function */
void CStandardMathLib_initialize(void)
{
  /* Registration code */

  /* initialize error status */
  rtmSetErrorStatus(CStandardMathLib_M, (NULL));

  /* external inputs */
  (void)memset(&CStandardMathLib_U, 0, sizeof(ExtU_CStandardMathLib_T));

  /* external outputs */
  (void)memset(&CStandardMathLib_Y, 0, sizeof(ExtY_CStandardMathLib_T));
}

/* Model terminate function */
void CStandardMathLib_terminate(void)
{
  /* (no terminate code required) */
}

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