Conteúdo do Curso

C Preprocessing

1. Introduction to Preprocessing

Introduction to Compilation Stages Role of the Preprocessor Preprocessing Commands

2. Macros

Symbolic Constant Macro With Arguments Advanced Usage of Symbolic Constant Cancel Macro Stringify Operators

3. Conditional compilation

Fundamentals of Conditional Compilation Pitfalls and Best Practices

Advanced Usage of Symbolic Constant

Let's consider practical examples of using macro substitutions.

Multi-Line Macro

The \ (backslash) character in macros is used to continue the macro definition to the next line.

main


              1234567891011
            
#include <stdio.h>

#define PRINT_SUM(a, b)  \
    int sum = (a) + (b); \
printf("Sum: %d\n", sum);

int main() 
{
    PRINT_SUM(3, 5); // Call a macro that prints "Sum: 8"
    return 0;
}

Code duplication

This code uses the #define macro to shorten and avoid duplication of the same fields in two structures (struct Product and struct Customer)

main


              1234567891011121314151617181920212223242526272829
            
#include <stdio.h>
#define COMMON_FIELDS \
    int id;          \
    char name[50];   \
    float price;

// Declare the Product structure
struct Product 
{
    COMMON_FIELDS  // Using the macro
    char category[30];
};

// Declare the Customer structure
struct Customer 
{
    COMMON_FIELDS  // Using the macro
    char email[50];
    char address[100];
};
int main() 
{
    struct Product p1 = {1, "Laptop", 999.99, "Electronics"};
    struct Customer c1 = {2, "Alice", 0.0, "alice@example.com", "123 Main St"};

    printf("Product: %s,\n Category: %s,\n Price: %.2f\n", p1.name, p1.category, p1.price);
    printf("Customer: %s,\n Email: %s,\n Address: %s\n", c1.name, c1.email, c1.address);
    return 0;
}

Checking Logical Conditions

The macro automatically replaces the validation code without the need to write it manually and allows you to display useful information about the error.

main


              123456789101112
            
#include <stdio.h>
#define CHECK(condition) \
    if (!(condition)) { \
        printf("Error: %s not running!\n", #condition); \
}

int main() {
    int x = 5;
    CHECK(x > 0);   // Executes without error
    CHECK(x == 10); // Print an error message
    return 0;
}

Logging

The LOG_LEVEL macro sets the logging level (LOG_WARNING). Only ERROR and WARNING level messages will be output, and INFO will be ignored.

main


              1234567891011121314151617181920212223242526272829303132
            
#include <stdio.h>
// Defining logging levels
#define LOG_ERROR   1            // For critical errors
#define LOG_WARNING 2            // For reporting potential problems
#define LOG_INFO    3            // For general information about program execution
#define LOG_LEVEL   LOG_WARNING  // Set the desired logging level

void log_message(int level, const char *message) 
{
    if (level <= LOG_LEVEL) {    // Condition for checking the logging level
        switch (level) {
            case LOG_ERROR:
                printf("ERROR: %s\n", message);
                break;
            case LOG_WARNING:
                printf("WARNING: %s\n", message);
                break;
            case LOG_INFO:
                printf("INFO: %s\n", message);
                break;
            default:
                break;
        }
    }
}
int main() 
{
    log_message(LOG_ERROR, "This is an error message");
    log_message(LOG_WARNING, "This is a warning message");
    log_message(LOG_INFO, "This is an info message");
    return 0;
}

Tarefa

Swipe to start coding

Add a new logging level.

Set the logging level for LOG_DEBUG;
Set the desired logging level;
Set a condition that checks whether a message should be output for a specific logging level;
Specify the message text that will be displayed if the condition is not met.

Solução

Mude para o desktop para praticar no mundo realContinue de onde você está usando uma das opções abaixo

Tudo estava claro?

Obrigado pelo seu feedback!

Seção 2. Capítulo 3

Advanced Usage of Symbolic Constant

Let's consider practical examples of using macro substitutions.

Multi-Line Macro

The \ (backslash) character in macros is used to continue the macro definition to the next line.

main


              1234567891011
            
#include <stdio.h>

#define PRINT_SUM(a, b)  \
    int sum = (a) + (b); \
printf("Sum: %d\n", sum);

int main() 
{
    PRINT_SUM(3, 5); // Call a macro that prints "Sum: 8"
    return 0;
}

Code duplication

This code uses the #define macro to shorten and avoid duplication of the same fields in two structures (struct Product and struct Customer)

main


              1234567891011121314151617181920212223242526272829
            
#include <stdio.h>
#define COMMON_FIELDS \
    int id;          \
    char name[50];   \
    float price;

// Declare the Product structure
struct Product 
{
    COMMON_FIELDS  // Using the macro
    char category[30];
};

// Declare the Customer structure
struct Customer 
{
    COMMON_FIELDS  // Using the macro
    char email[50];
    char address[100];
};
int main() 
{
    struct Product p1 = {1, "Laptop", 999.99, "Electronics"};
    struct Customer c1 = {2, "Alice", 0.0, "alice@example.com", "123 Main St"};

    printf("Product: %s,\n Category: %s,\n Price: %.2f\n", p1.name, p1.category, p1.price);
    printf("Customer: %s,\n Email: %s,\n Address: %s\n", c1.name, c1.email, c1.address);
    return 0;
}

Checking Logical Conditions

The macro automatically replaces the validation code without the need to write it manually and allows you to display useful information about the error.

main


              123456789101112
            
#include <stdio.h>
#define CHECK(condition) \
    if (!(condition)) { \
        printf("Error: %s not running!\n", #condition); \
}

int main() {
    int x = 5;
    CHECK(x > 0);   // Executes without error
    CHECK(x == 10); // Print an error message
    return 0;
}

Logging

The LOG_LEVEL macro sets the logging level (LOG_WARNING). Only ERROR and WARNING level messages will be output, and INFO will be ignored.

main


              1234567891011121314151617181920212223242526272829303132
            
#include <stdio.h>
// Defining logging levels
#define LOG_ERROR   1            // For critical errors
#define LOG_WARNING 2            // For reporting potential problems
#define LOG_INFO    3            // For general information about program execution
#define LOG_LEVEL   LOG_WARNING  // Set the desired logging level

void log_message(int level, const char *message) 
{
    if (level <= LOG_LEVEL) {    // Condition for checking the logging level
        switch (level) {
            case LOG_ERROR:
                printf("ERROR: %s\n", message);
                break;
            case LOG_WARNING:
                printf("WARNING: %s\n", message);
                break;
            case LOG_INFO:
                printf("INFO: %s\n", message);
                break;
            default:
                break;
        }
    }
}
int main() 
{
    log_message(LOG_ERROR, "This is an error message");
    log_message(LOG_WARNING, "This is a warning message");
    log_message(LOG_INFO, "This is an info message");
    return 0;
}

Tarefa

Swipe to start coding

Add a new logging level.

Set the logging level for LOG_DEBUG;
Set the desired logging level;
Set a condition that checks whether a message should be output for a specific logging level;
Specify the message text that will be displayed if the condition is not met.

Solução

Mude para o desktop para praticar no mundo realContinue de onde você está usando uma das opções abaixo

Tudo estava claro?

Obrigado pelo seu feedback!

Seção 2. Capítulo 3

Mude para o desktop para praticar no mundo realContinue de onde você está usando uma das opções abaixo