CodeGeneration

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---
title: CodeGeneration
---

Code generation in C with the pre-processor.

# Applied X-Macros

*   Based on [luser-droog][1]'s [answer][2] on StackOverflow 
*   Code generation with Meta-X-Macros

#include <stdio.h>
    
    #define ERRORS(_) \
        _(NO_ERROR, 0x00) \
        /* discontiguous  */ \
        _(EMPTY, 0x02) \
        _(OVERFLOW, 0x03) \
        _(TIMEOUT, 0x04) \
    
    /** X-Macro to define ERROR_<FOO> enum entries */
    #define AS\_ENUM(name, ID) ERROR\_##name = ID,
    /** X-Macro to define {"ERROR_FOO", ID} struct table entries */
    #define AS_LIST(name, ID) {#name, ID},
    
    /** Register Enum */
    enum ERROR {
        /* Generate enum elements with X-Macro */
        ERRORS(AS_ENUM)
    
        ERROR_MAX
    };
    
    /**
     * Error List Generated by X-Macro @ref AS_LIST.
     *
     * Works with non-contiguous sets.
     */
    static const struct ErrorEntry {
        char* name;
        enum ERROR id;
    } ERROR_LIST[] = {
        ERRORS(AS_LIST)
    };
    
    void PrintAll(void)
    {
        size_t idx = ;
    
        for (idx = ;
             idx < sizeof(ERROR_LIST)/sizeof(ERROR_LIST[]);
             idx++)
        {
            const struct ErrorEntry* reg = &ERROR_LIST[idx];
            printf("Error message 0x%x is \"%s\"\n", reg->id, reg->name);
        }
    }
    
    int main(void)
    {
        PrintAll();
    }

## Method

1.  ERRORS(AS_ENUM) expands to enum ERROR {
            /* Generate enum elements with X-Macro */
            AS_ENUM(NO_ERROR, 0x00) \
            AS_ENUM(EMPTY, 0x02) \
            ...
        
            ERROR_MAX
        };

2.  Each of these is then expanded again by the preprocessor to enum ERROR {
            ERROR\_NO\_ERROR = 0x00,
            ERROR_EMPTY = 0x02,
            ...
        
            ERROR_MAX
        };

3.  Similar expansion applies for the ERROR_LIST struct list entries

# Protocol Messages

*   Generate struct serialization/deserialization routines 
*   <https://github.com/cognomen/C-MsgGen>

[1]: http://stackoverflow.com/users/733077/luser-droog
 [2]: http://stackoverflow.com/a/6636596
 [4]: CodeGeneration?action=sourceblock&num=1
 [5]: CodeGeneration?action=sourceblock&num=2
 [6]: CodeGeneration?action=sourceblock&num=3

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