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| − | {{c title|C11}}{{C standards}}
| + | '''C11''' is the latest major revision of the C standard ratified by ISO on December 8, 2011 by the the international standardization working group for the programming language C, ''ISO/IEC JTC1/SC22/WG14''<ref>[http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=57853 Information technology -- Programming languages -- C]</ref>. C11 obsoletes the previous standard, C99, published in 1999. In April of 2011 the final draft ([http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf N1570]) was published. The draft passed its final review on October 10, 2011 which was consequently ratified and published as '''ISO/IEC 9899:2011'''. C11 was also later adopted by INCITS as an ANSI standard on May 23, 2012 as '''INCITS/ISO/IEC 9899-2012'''<ref>[http://webstore.ansi.org/RecordDetail.aspx?sku=INCITS%2FISO%2FIEC+9899-2012 INCITS/ISO/IEC 9899-2012]</ref>. |
| − | '''C11''' is the latest major revision of the [[C]] standard which was ratified by ISO on December 8, 2011 by the the international standardization working group for the [[C]] programming language, ''ISO/IEC JTC1/SC22/WG14''<ref>[http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=57853 Information technology -- Programming languages -- C]</ref>. C11 obsoletes the previous standard, C99, published in 1999. In April of 2011 the final draft ([http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf N1570]) was published. The draft passed its final review on October 10, 2011 which was consequently ratified and published as '''ISO/IEC 9899:2011'''. C11 was also later adopted by INCITS as an ANSI standard on May 23, 2012 as '''INCITS/ISO/IEC 9899-2012'''<ref>[http://webstore.ansi.org/RecordDetail.aspx?sku=INCITS%2FISO%2FIEC+9899-2012 INCITS/ISO/IEC 9899-2012]</ref>. | |
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| − | The C11 standard adds concurrency support, provides a mechanism for {{C|generic selection|type-generic expressions}}, adds alignment-related facilities, {{C|static assertion}}, Unicode support, floating-point characteristic macros, no-return functions, anonymous structures and unions
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| − | , and various bound-checking and reentrancy functions.
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| − | == Version detection ==
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| − | C11 can be detected via the '''__STDC_VERSION__''' mandatory macro and the '''__STDC_LIB_EXT1__''' conditional feature macro which must equal ''201112L''. Note that the official standard has a defect where the macro's definition is set to '201ymmL'. The defect has been corrected in Defect Report [http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_411.htm #411].
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| − | <source lang="C">
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| − | #if __STDC_VERSION__ >= 201112L
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| − | /* C11 support */
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| − | #endif
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| − | </source>
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| − | == New headers ==
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| − | C11 introduces 5 new [[C standard library|standard headers]]: <[[stdalign.h]]>, <[[stdatomic.h]]>, <[[stdnoreturn.h]]>, <[[threads.h]]>, and <[[uchar.h]]>. The two concerned with concurrency (stdatomic.h and threads.h) are optional.
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| − | == No-return functions ==
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| − | Some functions do not ever return for various reasons. The new '''_Noreturn''' keyword can be used to mark functions that do not return to their caller such as ''exit()'', ''longjmp()'', and ''thrd_exit()''. Using _Noreturn can assist compiler's optimizers as well as eliminating possible diagnostic messages.
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| − | Note that the use of _Noreturn must be limited to functions that cannot return under any circumstance. No-return functions that may return under certain conditions will exhibit undefined behavior.
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| − | == Alignment ==
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| − | {{main|c/alignment of objects|l1=Alignment of objects}}
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| − | C11 provides a new mechanism for working with objects alignments. The '''_Alignof''' operator was added which yields the alignment requirement (an integer constant) of its operand type (which remains unevaluted). A set of convenient macros such as ''alignof'' and ''alignas'' are defined in [[stdalign.h|<stdalign.h>]].
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| − | For example:
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| − | <source lang="C">printf("The alignment of char is %zd.\n", _Alignof (char));</source>
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| − | Which must print 1 for the alignment of char. Additionally, the alignment can be specified as an integer using the '''_Alignas''' alignment specifier.
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| − | On each platform, a some type has the largest alignment requirement. C11 added the '''max_align_t''' object type whose alignment is as great as is supported by the implementation.
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| − | === Extended alignment ===
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| − | Extended alignment is the ability for an implementation to support alignment requirement greater than _Alignof (max_align_t). A type having extended alignment requirement is called an ''over-aligned type''. That feature is optional and need not be supported.
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| − | == Aligned memory allocations ==
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| − | C11 added the {{C|stdlib.h/aligned_alloc|aligned_alloc}} function which allocates space for an object whose alignment is provided by you.
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| − | == Unicode support ==
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| − | C11 adds support for Unicode characters and string literals. A set of prefixes have been added to support [[UTF-8]], [[UTF-16]], and [[UTF-32]] character strings. The ''u8'' prefix for strings creates a UTF-8 encoded string. Likewise the ''u'' and ''U''' prefixes create UTF-16 and UTF-32 strings respectively. For example:
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| − | <source lang="C">
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| − | #include <uchar.h>
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| − | /* UTF-8 */
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| − | char u8str[] = u8"ππ This is a UTF-8 string ππ.";
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| − | char u8chr = u8'π';
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| − | /* UTF-16 */
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| − | #ifdef __STD_UTF_16__
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| − | char16_t u16str[] = u"ΩΩ This is a UTF-16 string ΩΩ.";
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| − | char16_t u16char = u'Ω';
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| − | #endif
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| − | /* UTF-32 */
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| − | #ifdef __STD_UTF_32__
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| − | char32_t u32str[] = U"δδ This is a UTF-32 string δδ.";
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| − | char32_t u32char = U'δ';
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| − | #endif
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| − | </source>
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| − | == Type-generic expressions ==
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| − | {{main|c/generic selection|l1=Generic selection}}
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| − | C11 now provides a mechanism for type-generic expressions, a mechanism needed to perform type-generic math without compiler magic. The feature is achieved via the addition of the new '''_Generic''' keyword.
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| − | == Static assertion ==
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| − | {{main|c/static assertion|l1=Static assertion}}
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| − | C11 added support for compile-time assertions. Static assertions are evaluated after the preprocessor compilation phase is over, thereby allowing the use of C operators such as ''sizeof''.
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| − | == Bounds-checking interfaces annex (Annex K) ==
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| − | The Bounds-checking interfaces annex provides a set of functions with more restricted behaviors in order to allow for more secure coding practices.
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| − | === Reentrant functions ===
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| − | The functions ''strtok_s'', ''wcstok_s'', ''bsearch_s'', and ''qsort_s'', were added, which keep track of their state via an argument that is passed instead of a static buffer to ensure they are reentrant.
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| − | === %n format specifier ===
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| − | In various format printing functions, all %specifiers with the exception of %n are used for output purpose. On the other hand, the %n specifier is user for input. The ''_s'' version of the functions was added, which gets rid of the %n specifier entirely.
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| − | === memset_s ===
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| − | The memset_s function is a special version of memset that must execute even if the compiler's optimizer considers it superfluous. The best case for this is when a function attempts to zero-out some confidential information such as a password right before returning, thus making the optimizer think that the memset is not doing anything.
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| − | == Analyzability annex (Annex L) ==
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| − | The Analyzability Annex identifies a small subset of all undefined behaviors and sets some implementation constraints on the resulting behavior in an attempt to mitigate potential issues. An implementation that conforms to Annex L must define '''__STDC_ANALYZABLE__'''.
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| − | == Concurrency ==
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| − | {{main|c/concurrency|l1=Concurrency}}
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| − | C11's largest addition to the C programming language, is the addition of semantics of multi‐threaded programs. The standard also added a facility for performing inter‐thread communication via atomic variables as well as thread-specific storage. Thread support is optional and must be tested for via the '''__STDC_NO_THREADS__''' macro.
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| − | == Compiler support ==
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| − | {| class="wikitable"
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| − | |-
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| − | | style="background:#CCCCFF;text-align:center;" colspan="4" | C11 Compiler Support
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| − | ! Compiler Name !! Support Level !! style="text-align:center;" | Enforcement Switch !! Note
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| − | |-
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| − | | ACK || style="background:#FF6666;text-align:center;" | No Support || ||
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| − | |-
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| − | | Clang || style="background:#99FF66;text-align:center;" | Supported || style="text-align:center;" | -std=c11 || No support for (optional) <threads.h>
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| − | |-
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| − | | GCC || style="background:#99FF66;text-align:center;" | Supported || style="text-align:center;" | -std=c11<ref>[http://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html Options Controlling C Dialect]</ref> || No support for (optional) <threads.h><ref>[http://gcc.gnu.org/wiki/C11Status C11 Status]</ref>
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| − | |-
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| − | | TCC || style="background:#FFCC66;text-align:center;" | Partial || ||
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| − | |-
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| − | | ICC || style="background:#FFCC66;text-align:center;" | Partial || style="text-align:center;" | ||
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| − | |-
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| − | | Visual C++ || style="background:#FFCC66;text-align:center;" | Partial || || Missing most headers
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| − | |}
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| | == References == | | == References == |
| | {{reflist}} | | {{reflist}} |
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| − | == External links ==
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| − | * [http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1570.pdf C11 final draft]
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| − | [[Category:C standards]]
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