c++ - cout 语句中首先运行的是什么？ (C++17)

Question

比如说我有一个很长的陈述

cout << findCurrent() << "," << findLowest() << "," << findHighest() << "," << findThird()<<"\n";

会findCurrent()在 findLowest() 之前运行喜欢逻辑吗？

Answer 1

自 C++17 起，函数保证从左到右调用，即 findCurrent()首先被调用，然后是findLowest()等等。

C++17 标准引用:[expr.shift]/4(指表达式 E1 << E2):

The expression E1 is sequenced before the expression E2.

[over.match.oper]/2:(描述重载运算符)

the operands are sequenced in the order prescribed for the built-in operator.

[介绍.执行]/15:

An expression X is said to be sequenced before an expression Y if every value computation and every side effect associated with the expression X is sequenced before every value computation and every side effect associated with the expression Y.

Link to cppreference summary

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在 C++17 之前，函数调用的顺序是未指定，这意味着它们可以以任何顺序调用(并且这个顺序在重复调用时不需要相同)。