Preprocessor and #define Directive During the C++ compilation process, the source code is first passed to the preprocessor. #define is a preprocessor directive used to create symbol constants (also known as macro constants). Basic Syntax #define identifier replacement_text Basic Usage Example #include <iostream> using namespace std; // Using #define to define symbol constants #define MAX_SIZE … Read more
In the Linux kernel source code, the keywords likely and unlikely are frequently encountered. Upon examining the source code, it turns out that these two keywords are macros defined in the include/linux/compiler.h file of the kernel source (specifically in linux-3.11.0-rc1): Since CONFIG_PROFILE_ALL_BRANCHES is not defined, the definitions of the two macros are as follows: # … Read more
Let’s first take a look at the following piece of code. What do you think the output will be? #include <stdio.h> #define add(x) x + x int main(){ int ret = add(2) * 10; printf("%d", ret); return 0; } To understand the output of this program, we must discuss macros.This is the official explanation of … Read more
View Builder Syntax Without Macros If you are completely satisfied with the <span>view!</span> macro syntax described earlier, you can skip this chapter. The builder syntax described in this section is always available but is never mandatory. For various reasons, many developers prefer to avoid using macros. Perhaps you dislike the limited <span>rustfmt</span> support (though you … Read more
⭐Understanding C Language Header Files and Macro Definitions: Grasping <span>#include</span> and <span>#define</span> and ‘Include Guards’ Author: IoT Smart Academy Continuing from previous comprehensive projects: We have already used the <span>student.h / student.c / main.c</span> multi-file structure, and have also written #ifndef STUDENT_H #define STUDENT_H … #endif However, many students actually just “copy and use” without … Read more
Table of Contents 1. Introduction 2. Common Solutions: Basic Form of Macros 3. Dangerous Macros 4. The Real Reason: Array Decay 5. Solution – Enhanced Macros 6. Conclusion: From Usable to Robust 1. Introduction In our daily embedded development, arrays are a data structure we cannot avoid. Whether defining a buffer or a configuration table, … Read more
Word count: 576, reading time approximately 3 minutes Zig C++ Interop[1] discusses interoperability between Zig and C++, particularly the issue of sharing data types between the two languages. The author’s goal is to allow both Zig and C to store each other’s data types within their respective structures/classes, without needing to define all Zig types … Read more
1. The Art of Macro Programming in the Linux Kernel The Linux kernel is a prime example of macro programming, demonstrating how to achieve elegant and efficient code using macros. 1.1 Type-Safe <span>min</span> / <span>max</span> Macros The standard <span>MIN/MAX</span> macros have side effects and type issues: // Dangerous traditional macros #define MIN(a, b) ((a) < … Read more
Embedded engineers commonly use macros when coding in C language and debugging. Through continuous engineering experience, I have summarized many useful macros that can be applied to most embedded C language projects, ensuring high portability and readability. Below are some commonly used macros that engineers can save for future use as needed! 1. Preventing a … Read more
1. Essence of Macros The preprocessor is the first step in the C language compilation process, performing text replacement on the source code before actual compilation. Macro definitions are a form of string replacement mechanism that does not involve type checking or semantic analysis. Compilation Process: Source Code → Preprocessing → Compilation → Assembly → … Read more