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C17 is the informal name for ISO/IEC 9899:2018, [1] the most recent standard for the C programming language, prepared in 2017 and published in June 2018. It replaced C11 (standard ISO/IEC 9899:2011), [2] and will be superseded by C23 (ISO/IEC 9899:2023) when it is published in 2024. [3] Since it was under development in 2017, and officially published in 2018, C17 is sometimes referred to as C18. [4]
C17 fixes numerous minor defects in C11 without introducing new language features. [2]
The __STDC_VERSION__
macro is increased to the value 201710L
.
For a detailed list of changes from the previous standard, see Clarification Request Summary for C11. [5]
List of compilers supporting C17:
ANSI C, ISO C, and Standard C are successive standards for the C programming language published by the American National Standards Institute (ANSI) and ISO/IEC JTC 1/SC 22/WG 14 of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). Historically, the names referred specifically to the original and best-supported version of the standard. Software developers writing in C are encouraged to conform to the standards, as doing so helps portability between compilers.
The GNU Compiler Collection (GCC) is an optimizing compiler produced by the GNU Project supporting various programming languages, hardware architectures and operating systems. The Free Software Foundation (FSF) distributes GCC as free software under the GNU General Public License. GCC is a key component of the GNU toolchain and the standard compiler for most projects related to GNU and the Linux kernel. With roughly 15 million lines of code in 2019, GCC is one of the biggest free programs in existence. It has played an important role in the growth of free software, as both a tool and an example.
The C preprocessor is the macro preprocessor for several computer programming languages, such as C, Objective-C, C++, and a variety of Fortran languages. The preprocessor provides inclusion of header files, macro expansions, conditional compilation, and line control.
The C standard library or libc is the standard library for the C programming language, as specified in the ISO C standard. Starting from the original ANSI C standard, it was developed at the same time as the C library POSIX specification, which is a superset of it. Since ANSI C was adopted by the International Organization for Standardization, the C standard library is also called the ISO C library.
In the C and C++ programming languages, an inline function is one qualified with the keyword inline
; this serves two purposes:
register
storage class specifier, which similarly provides an optimization hint.inline
is to change linkage behavior; the details of this are complicated. This is necessary due to the C/C++ separate compilation + linkage model, specifically because the definition (body) of the function must be duplicated in all translation units where it is used, to allow inlining during compiling, which, if the function has external linkage, causes a collision during linking. C and C++ resolve this in different ways.In computer programming, undefined behavior (UB) is the result of executing a program whose behavior is prescribed to be unpredictable, in the language specification to which the computer code adheres. This is different from unspecified behavior, for which the language specification does not prescribe a result, and implementation-defined behavior that defers to the documentation of another component of the platform.
C99 is an informal name for ISO/IEC 9899:1999, a past version of the C programming language standard. It extends the previous version (C90) with new features for the language and the standard library, and helps implementations make better use of available computer hardware, such as IEEE 754-1985 floating-point arithmetic, and compiler technology. The C11 version of the C programming language standard, published in 2011, updates C99.
A variadic macro is a feature of some computer programming languages, especially the C preprocessor, whereby a macro may be declared to accept a varying number of arguments.
Watcom C/C++ is an integrated development environment (IDE) product from Watcom International Corporation for the C, C++, and Fortran programming languages. Watcom C/C++ was a commercial product until it was discontinued, then released under the Sybase Open Watcom Public License as Open Watcom C/C++. It features tools for developing and debugging code for DOS, OS/2, and Windows, Linux operating systems, which are based upon x86, IA-32, x86-64 compatible processors.
In C and related programming languages, long double
refers to a floating-point data type that is often more precise than double precision though the language standard only requires it to be at least as precise as double
. As with C's other floating-point types, it may not necessarily map to an IEEE format.
assert.h is a header file in the C standard library. It defines the C preprocessor macro assert
and implements runtime assertion in C.
IAR Systems is a Swedish computer software company that offers development tools for embedded systems. IAR Systems was founded in 1983, and is listed on Nasdaq Nordic in Stockholm. IAR is an abbreviation of Ingenjörsfirma Anders Rundgren, which means Anders Rundgren Engineering Company.
Clang is a compiler front end for the C, C++, Objective-C, and Objective-C++ programming languages, as well as the OpenMP, OpenCL, RenderScript, CUDA, SYCL, and HIP frameworks. It acts as a drop-in replacement for the GNU Compiler Collection (GCC), supporting most of its compilation flags and unofficial language extensions. It includes a static analyzer, and several code analysis tools.
In computer programming, a variable-length array (VLA), also called variable-sized or runtime-sized, is an array data structure whose length is determined at run time . In C, the VLA is said to have a variably modified type that depends on a value.
C11 is an informal name for ISO/IEC 9899:2011, a past standard for the C programming language. It replaced C99 and has been superseded by C17. C11 mainly standardizes features already supported by common contemporary compilers, and includes a detailed memory model to better support multiple threads of execution. Due to delayed availability of conforming C99 implementations, C11 makes certain features optional, to make it easier to comply with the core language standard.
Concepts are an extension to the templates feature provided by the C++ programming language. Concepts are named Boolean predicates on template parameters, evaluated at compile time. A concept may be associated with a template, in which case it serves as a constraint: it limits the set of arguments that are accepted as template parameters.
C++17 is a version of the ISO/IEC 14882 standard for the C++ programming language. C++17 replaced the prior version of the C++ standard, called C++14, and was later replaced by C++20.
C++20 is a version of the ISO/IEC 14882 standard for the C++ programming language. C++20 replaced the prior version of the C++ standard, called C++17, and was later replaced by C++23. The standard was technically finalized by WG21 at the meeting in Prague in February 2020, had its final draft version announced in March 2020, was approved on 4 September 2020, and published in December 2020.
C23 is the informal name for ISO/IEC 9899:2024, the next standard for the C programming language, which will replace C17. It was started in 2016 informally as C2x, and expected to be published in 2024. The most recent publicly available working draft of C23 was released on April 1, 2023. The first WG14 meeting for the C2x draft was held in October 2019, virtual remote meetings were held in 2020 due to the COVID-19 pandemic, then various teleconference meetings continued to occur through 2024.
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