Ensuring Bits are Set to True: Exploring Options
When initializing an unsigned integer to set all its bits to true, developers often encounter a dilemma. Is it preferable to use -1, 0xffffffff, or ~0?
-1: A Straightforward Solution
Setting the variable to -1 is considered the most direct method. It assigns the highest possible value for an unsigned integer, effectively setting all bits to true. This approach is independent of the sign representation and works consistently.
0xffffffff and ~0: Potential Surprises
Using 0xffffffff or ~0 may lead to unexpected behavior. ~0 inverts all bits of the variable, yielding the desired -1 only when the variable is of unsigned int type. For other types, it may not result in the expected value. For instance, ~0u is necessary for setting all bits of an unsigned long to true.
Furthermore, ~0 on a non-two's complement machine will not yield -1. This can result in initializing the variable to zero instead of the desired highest value.
Conclusion
When the goal is to set all bits of an unsigned integer to true, the most reliable method is to assign -1. This approach is portable and works for all variable types and machine representations.
Avoiding Misconceptions
It's important to clarify that the true/false interpretation is misleading. -1 doesn't necessarily have all bits set to one, and ~0 always sets all bits to one. Instead, the focus should be on the value being set: -1 effectively initializes the variable to the highest possible unsigned value.
The above is the detailed content of How to Reliably Set All Bits of an Unsigned Integer to True?. For more information, please follow other related articles on the PHP Chinese website!

This article details C function return types, encompassing basic (int, float, char, etc.), derived (arrays, pointers, structs), and void types. The compiler determines the return type via the function declaration and the return statement, enforcing

Gulc is a high-performance C library prioritizing minimal overhead, aggressive inlining, and compiler optimization. Ideal for performance-critical applications like high-frequency trading and embedded systems, its design emphasizes simplicity, modul

This article explains C function declaration vs. definition, argument passing (by value and by pointer), return values, and common pitfalls like memory leaks and type mismatches. It emphasizes the importance of declarations for modularity and provi

This article details C functions for string case conversion. It explains using toupper() and tolower() from ctype.h, iterating through strings, and handling null terminators. Common pitfalls like forgetting ctype.h and modifying string literals are

This article examines C function return value storage. Small return values are typically stored in registers for speed; larger values may use pointers to memory (stack or heap), impacting lifetime and requiring manual memory management. Directly acc

This article analyzes the multifaceted uses of the adjective "distinct," exploring its grammatical functions, common phrases (e.g., "distinct from," "distinctly different"), and nuanced application in formal vs. informal

This article details efficient STL algorithm usage in C . It emphasizes data structure choice (vectors vs. lists), algorithm complexity analysis (e.g., std::sort vs. std::partial_sort), iterator usage, and parallel execution. Common pitfalls like

This article explains the C Standard Template Library (STL), focusing on its core components: containers, iterators, algorithms, and functors. It details how these interact to enable generic programming, improving code efficiency and readability t


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

WebStorm Mac version
Useful JavaScript development tools

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

Dreamweaver CS6
Visual web development tools

Atom editor mac version download
The most popular open source editor

SublimeText3 English version
Recommended: Win version, supports code prompts!
