C11

ISO/IEC 9899:2011, a.k.a. C11, is a previous revision of the C standard.

Obsolete

Removed

• gets()

New language features

• Multithreaded environments
  • Atomic objects (_Atomic)
  • Thread local storage (_Thread_local)
• Enhanced alignment support
  • Alignment query (_Alignof)
  • Alignment strengthening (_Alignas)
  • Over-aligned types
• Unicode support
  • u/U character constants
  • u8/u/U string literals
• Generic selection expressions (_Generic)
• Non-returning functions (_Noreturn)
• Anonymous struct and union members
• Fine-grained evaluation order
• Extending the lifetime of temporary objects
• _Static_assert
• Analyzability

Feature test macros for optional features

• __STDC_ANALYZABLE__
  • Indicates analyzability is supported.
• __STDC_LIB_EXT1__
  • Indicates bounds checking functions are supported.
• __STDC_NO_ATOMICS__
  • Indicates atomic objects and the atomic operation library are not supported.
• __STDC_NO_COMPLEX__
  • Indicates complex types and the complex math functions are not supported.
  These features were mandatory in C99.
• __STDC_NO_THREADS__
  • Indicates thread local storage and the thread support library are not supported.
• __STDC_NO_VLA__
  • Indicates variable length arrays and variably modified types are not supported.
  These features were mandatory in C99.

New library features

New headers

• <stdalign.h>
• <stdatomic.h>
• <stdnoreturn.h>
• <threads.h>
• <uchar.h>

Library features

• Concurrency support library
• aligned_alloc()
• UTF-16/32 type aliases
  • char16_t
  • char32_t
• UTF-16/32 conversion functions
  • mbrtoc16()
  • mbrtoc32()
  • c16rtomb()
  • c32rtomb()
• quick_exit
• at_quick_exit
• Exclusive modes of fopen() and freopen() ("x")
• Bounds checking functions
• timespec
• timespec_get()
• CMPLX(F|L)?
• New numeric limit macros
  • (FLT|DBL|LDBL)_DECIMAL_DIG
  • (FLT|DBL|LDBL)_TRUE_MIN
  • (FLT|DBL|LDBL)_HAS_SUBNORM
• Thread local errno

Defect reports

Template:c/language/history/DR11.

Compiler support

Template:c/compiler support/11.