Implementation defined behavior control

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C++
 
C + +语言
大会的主题
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General topics
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流量控制
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Flow control
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条件执行语句
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Conditional execution statements
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迭代语句
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Iteration statements
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跳转语句
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Jump statements
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功能
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Functions
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函数声明
lambda函数的声明
函数模板
的历史。内嵌说明
异常规范 （过时了）
noexcept说明 （C++11）
例外
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Exceptions
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命名空间
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Namespaces
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类型
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Types
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decltype specifier （C++11）
规范
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Specifiers
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CV符
存储时间说明符
constexpr说明 （C++11）
汽车符 （C++11）
alignas说明 （C++11）
初始化
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Initialization
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常
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Literals
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布尔文字
nullptr （C++11）
用户定义的 （C++11）
表达式
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Expressions
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另一种表示形式
实用工具
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Utilities
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类型
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Types
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typedef declaration
声明类型别名 （C++11）
属性 （C++11）
施放
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Casts
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隐式转换
const_cast conversion
static_cast conversion
dynamic_cast conversion
reinterpret_cast conversion
C-风格和功能转换
内存分配
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Memory allocation
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类
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Classes
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类特定的功能特性
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Class-specific function properties
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虚函数
覆盖说明 （C++11）
最后说明 （C++11）
明确的 （C++11）
静态的
特殊的成员函数
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Special member functions
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模板
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Templates
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类模板
函数模板
模板特化
参数包 （C++11）
杂项
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Miscellaneous
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内联汇编
 
预处理器
 
实现定义的行为是由#pragma指令.
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Implementation defined behavior is controlled by #pragma directive.
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目录

[编辑] 语法

#pragma pragma_params

[编辑] 解释

pragma指令控制的编译器，，如禁用编译器警告或改变对齐的要求，实施特定的行为。未确认任何杂忽视
Original:
Pragma directive controls implementation-specific behavior of the compiler, such as disabling compiler warnings or changing alignment requirements. Any pragma that is not recognized is ignored.
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[编辑] 标准指示

以下三个pragma的语言标准被定义为：1
Original:
The following three pragmas are defined by the language standard:
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#pragma STDC FENV_ACCESS arg (1)
#pragma STDC FP_CONTRACT arg (2)
#pragma STDC CX_LIMITED_RANGE arg (3)
arg是ON或OFFDEFAULT.
Original:
where arg is either ON or OFF or DEFAULT.
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1)
如果设置为ON，告诉编译器，该计划将浮点环境，这意味着优化，可以颠覆标志测试和模式的变化（例如，全局公共子表达式消除，代码运动和常量折叠）禁止访问或修改。默认值是实现定义的，通常OFF.
Original:
If set to ON, informs the compiler that the program will access or modify 浮点环境, which means that optimizations that could subvert flag tests and mode changes (e.g., global common subexpression elimination, code motion, and constant folding) are prohibited. The default value is implementation-defined, usually OFF.
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2)
允许“承包”的浮点表达式，即忽略舍入误差浮点异常，如果完全按照书面的表达进行了评估，将观察的优化。默认值是实现定义的，通常ON.
Original:
Allows contracting of floating-point expressions, that is optimizations that omit rounding errors and floating-point exceptions that would be observed if the expression was evaluated exactly as written. The default value is implementation-defined, usually ON.
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3)
通知编译器，乘法，除法，复数的绝对值可能会使用最简单的数学公式，尽管中间溢出的可能性。传递给这些函数的值的范围内被预期是有限的。默认值是OFF
Original:
Informs the compiler that multiplication, division, and absolute value of complex numbers may use simplified mathematical formulas, despite the possibility of intermediate overflow. The range of the values passed to those function is expected to be limited. The default value is OFF
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[编辑] 外部链接

来自“http://zh.cppreference.com/mwiki/index.php?title=cpp/preprocessor/impl&oldid=26596”