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In C and C++, volatile is a type qualifier, like const, and is a part of a type (e.g. the type of a variable or field). The behavior of the volatile keyword in C and C++ is sometimes given in terms of suppressing optimizations of an optimizing compiler: 1- don't remove existing volatile reads and writes, 2- don't add new volatile reads and writes, and 3- don't reorder volatile reads and writes.
As of 2014 and C11, there are four type qualifiers in standard C: const , volatile , restrict and _Atomic – the latter has a private name to avoid clashing with user names, [14] but the more ordinary name atomic can be used if the <stdatomic.h> header is included.
The first two of these, const and volatile, are also present in C++, and are the only type qualifiers in C++. Thus in C++ the term " cv -qualified type" (for c onst and v olatile) is often used for "qualified type", while the terms " c -qualified type" and " v -qualified type" are used when only one of the qualifiers is relevant.
There are valid forms of the pattern, including the use of the volatile keyword in Java and explicit memory barriers in C++. [4] The pattern is typically used to reduce locking overhead when implementing "lazy initialization" in a multi-threaded environment, especially as part of the Singleton pattern. Lazy initialization avoids initializing a ...
In C and C++, the volatile keyword was intended to allow C and C++ programs to directly access memory-mapped I/O. Memory-mapped I/O generally requires that the reads and writes specified in source code happen in the exact order specified with no omissions. Omissions or reorderings of reads and writes by the compiler would break the ...
The three canonical correct uses of volatile in C/C++ are signal handlers, setjmp longjmp, and and MMIO. Yours is clearly the signal handler use case. (Using volatile in C/C++ in anything other than one of these three canonical use cases is almost certainly incorrect.) 32.140.104.214 ( talk ) 11:36, 28 August 2024 (UTC) [ reply ]
A hot December jobs report, combined with a murky inflation outlook for 2025, has some economists debating if the Federal Reserve may need to hike interest rates again.
C++20 is a version of the ISO/IEC 14882 standard for the C++ programming language. ... Most of the uses of the volatile keyword have been deprecated. [59]