ConfigDefines

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---
title: ConfigDefines
---

Quick, tidy, feature #defines.

*   Centralizes build-time configuration. 
*   Imports a list of #defines from Config.inc and applies a set of rules defining dependent features.

Convenience macros are provided in order to free code from #ifdef clutter, allowing one to write

if (have(SOME_FEATURE))
        use_some_feature();

instead of

#if defined SOME_FEATURE
         use_some_feature();
      #endif

Also allows configuration tests to be combined more naturally with conditional syntax. e.g.

if (have(SOME_FEATURE)
          && have(SOME_OTHER_FEATURE)
          && featureData != NULL)
      {
          use_the_features(featureData);
      }

## Config.h

#ifndef CONFIG_H
    #define CONFIG_H
    
    /* Current configuration */
    #include "Config.inc"
    
    /** 
     * Build-time configuration test.
     * e.g. if (have(SOME_FEATURE)) use_some_feature();
     *
     * Default build-time configuration is defined in Config.inc.
     *
     * @param C Configuration feature to test
     */
    #define have(C) HAVE_##C()
    
    /* ======================================================================== */
    /*   Configuration rules */
    /* ======================================================================== */
    
    /* Release features */
    #if defined CONFIG_RELEASE
        #define CONFIG_FEATURE_A
        #undef CONFIG_FEATURE_B
    #endif
    
    /* Default features */
    #if defined CONFIG_DEFAULT
        #define CONFIG_FEATURE_A
    #endif
    
    /* Maximum code coverage */
    #if defined CONFIG_ALL
        #define CONFIG_FEATURE_A
        #define CONFIG_FEATURE_B
    #endif
    
    /* ======================================================================== */
    /*   Configuration convenience macros. */
    /* ======================================================================== */
    
    /* Set: Enable feature A
     * Unset: Disable feature A
     * Depends: no dependent features
     */
    #if defined CONFIG_FEATURE_A
        #define HAVE_CONFIG_FEATURE_A() (1)
    #else
        #define HAVE_CONFIG_FEATURE_A() (0)
    #endif
    
    /* Set: Enable feature B
     * Unset: Disable feature B
     * Depends: no dependent features
     */
    #if defined CONFIG_FEATURE_B
        #define HAVE_CONFIG_FEATURE_B() (1)
    #else
        #define HAVE_CONFIG_FEATURE_B() (0)
    #endif
    
    #endif /* CONFIG_H */

## Config.inc

/* 
     * Default build-time configuration.
     *  See Config.h
     *
     */
    #define CONFIG_DEFAULT

# Notes

Variables that a feature depends on are either unused or would still need to be excluded from compilation with #ifdef. Or better, refactor the feature and its variables into their own compilation unit.

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