Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

#include <stdio.h>

/* Platform detection */
#if defined(_WIN32) || defined(_WIN64)
    #define PLATFORM "Windows"
    #define PATH_SEP '\\'
#elif defined(__APPLE__)
    #define PLATFORM "macOS"
    #define PATH_SEP '/'
#elif defined(__linux__)
    #define PLATFORM "Linux"
    #define PATH_SEP '/'
#else
    #define PLATFORM "Unknown"
    #define PATH_SEP '/'
#endif

/* Build configuration */
#ifdef DEBUG
    #define LOG(fmt, ...) \
        fprintf(stderr, "[DEBUG %s:%d] " fmt "
", \
                __FILE__, __LINE__, ##__VA_ARGS__)
#else
    #define LOG(fmt, ...)  /* no-op in release builds */
#endif

/* Version guard */
#define MY_VERSION 3
#if MY_VERSION < 2
    #error "Version 2 or higher is required"
#endif

/* C/C++ compatible header */
#ifdef __cplusplus
extern "C" {
#endif

void library_function(void);

#ifdef __cplusplus
}
#endif

void library_function(void)
{
    printf("library_function called on %s
", PLATFORM);
}

int main(void)
{
    printf("Platform:   %s
", PLATFORM);
    printf("Path sep:   '%c'
", PATH_SEP);
    printf("Version:    %d
", MY_VERSION);

LOG("main started, version=%d", MY_VERSION);
    library_function();

/* Compile with -DDEBUG to see LOG output */
    printf("Compile with -DDEBUG to enable debug logging.
");
    return 0;
}