订货在C，C初始化++ [英] Ordering in an initialization in C, C++

问题描述

考虑以下初始化：

/* C, C++ */
int a[] = { f(), g() };
struct { int x, y } foo = { f(), g() };

/* C++ */
struct goo { goo(int x, int y);  };

goo b = { f(), g() };
goo c { f(), g() };    /* C++11 */
goo d ( f(), g() );

时的顺序执行 F（）和克（）由C和C ++标准中规定的任何行？

Is the order of execution f() and g() in any line specified by C and C++ standards?

推荐答案

在所有这两种情况下

goo b = { f(), g() };
goo c { f(), g() };    /* C++11 */

从左至右和所有副作用应在下一个初始化之前施加评价的顺序确定

the order of evaluation is determined from left to right and all side effects shall be applied before the next initializer.

从C ++标准

4在一个支撑-INIT-列表的初始化列表，该
  初始化从句，包括任何由包扩张导致
  （14.5.3），在它们出现的顺序进行评估。那是，
  与给定的相关联的每一个值的计算和副作用
  每个值计算之前初始化从句被测序
  副作用与它后面的任何初始化，相关条款
  用逗号分隔的初始化列表清单。

4 Within the initializer-list of a braced-init-list, the initializer-clauses, including any that result from pack expansions (14.5.3), are evaluated in the order in which they appear. That is, every value computation and side effect associated with a given initializer-clause is sequenced before every value computation and side effect associated with any initializer-clause that follows it in the comma-separated list of the initializer-list.

但是用C还有其他规则

初​​始化列表前pressions的评价是
  相对于indeterminately测序以彼此并且因此
  其中出现的任何副作用顺序是不确定的。

The evaluations of the initialization list expressions are indeterminately sequenced with respect to one another and thus the order in which any side effects occur is unspecified.

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