difference between c99 and c11 [closed]

问题

I am learning c, presently. The book I read is C99 based. I want to update my knowledge to C11 after finishing this book, or change resource if there is a major difference. Thus, what I ask is for is an explanation or resource to update my knowledge. I only found this source. Nevertheless, it does not seem to encompass the information I need or not concise.

Thanks in advance. P.S: I want to learn C11 since I think it is the prevalent standard now. If not, please inform me.

回答1:

Good overviews of C11 standard:

https://en.wikipedia.org/wiki/C11_(C_standard_revision)
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
https://smartbear.com/blog/test-and-monitor/c11-a-new-c-standard-aiming-at-safer-programming/

The standard includes several changes to the C99 language and library specifications, such as:

Alignment specification (_Alignas specifier, _Alignof operator, aligned_alloc function, <stdalign.h> header file)
The _Noreturn function specifier and the <stdnoreturn.h> header file
Type-generic expressions using the _Generic keyword. For example, the following macro cbrt(x) translates to cbrtl(x), cbrt(x) or cbrtf(x) depending on the type of x:
```
#define cbrt(x) _Generic((x), long double: cbrtl, \
                          default: cbrt, \
                          float: cbrtf)(x)
```
Multi-threading support (_Thread_local storage-class specifier, <threads.h> header including thread creation/management functions, mutex, condition variable and thread-specific storage functionality, as well as the _Atomic type qualifier and <stdatomic.h> for uninterruptible object access).
Improved Unicode support based on the C Unicode Technical Report ISO/IEC TR 19769:2004 (char16_t and char32_t types for storing UTF-16/UTF-32 encoded data, including conversion functions in <uchar.h> and the corresponding u and U string literal prefixes, as well as the u8 prefix for UTF-8 encoded literals).
Removal of the gets function, deprecated in the previous C language standard revision, ISO/IEC 9899:1999/Cor.3:2007(E), in favor of a new safe alternative, gets_s.
Bounds-checking interfaces (Annex K).
Analyzability features (Annex L).
More macros for querying the characteristics of floating point types, concerning subnormal floating point numbers and the number of decimal digits the type is able to store.
Anonymous structures and unions, useful when unions and structures are nested, e.g. in struct T { int tag; union { float x; int n; }; };.
Static assertions, which are evaluated during translation at a later phase than #if and #error, when types are understood by the translator.
An exclusive create-and-open mode ("…x" suffix) for open. This behaves like O_CREAT|O_EXCL in POSIX, which is commonly used for lock files.
The quick_exit function as a third way to terminate a program, intended to do at least minimal deinitialization if termination with exit fails.
Macros for the construction of complex values (partly because real + imaginary*I might not yield the expected value if imaginary is infinite or NaN).

回答2:

Per the C 2011 standard itself, here are the major changes from C99:

Foreword
...
6     This third edition cancels and replaces the second edition, ISO/IEC 9899:1999, as corrected by ISO/IEC 9899:1999/Cor 1:2001, ISO/IEC 9899:1999/Cor 2:2004, and ISO/IEC 9899:1999/Cor 3:2007. Major changes from the previous edition include:

     — conditional (optional) features (including some that were previously mandatory)

     — support for multiple threads of execution including an improved memory sequencing model, atomic objects, and thread-local storage (<stdatomic.h> and <threads.h>)

     — additional floating-point characteristic macros (<float.h>)

     — querying and specifying alignment of objects (<stdalign.h>, <stdlib.h>)

     — Unicode characters and strings (<uchar.h>) (originally specified in ISO/IEC TR 19769:2004)

     — type-generic expressions

     — static assertions

     — anonymous structures and unions

     — no-return functions

     — macros to create complex numbers (<complex.h>)

     — support for opening files for exclusive access

     — removed the gets function (<stdio.h>)

     — added the aligned_alloc, at_quick_exit, and quick_exit functions (<stdlib.h>)

     — (conditional) support for bounds-checking interfaces (originally specified in ISO/IEC TR 24731−1:2007)

     — (conditional) support for analyzability

来源：https://stackoverflow.com/questions/38405260/difference-between-c99-and-c11

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