c++ - Placement-new 是否引入了序列点？

Question

考虑以下代码行:

new (p++) T();

如果构造函数T()抛出异常，是否保证p已经自增？

Answer 1

来自 5.3.4 [expr.new](引自 n3242):

11 The new-placement syntax is used to supply additional arguments to an allocation function. If used, overload resolution is performed on a function call created by assembling an argument list consisting of the amount of space requested (the first argument) and the expressions in the new-placement part of the new-expression (the second and succeeding arguments).

所以在一个新的表达式中，分配函数是从函数调用中使用的(这是有道理的)。所有分配函数都是函数，包括实现提供的函数，来自 3.7.4.1 [basic.stc.dynamic.allocation]:

1 An allocation function shall be a class member function or a global function; [...]

所以当构造函数抛出异常时，分配已经发生并且相关的函数调用表达式已经被完全评估。