问题
Is it safe to use std::cout in constructors of objects with statc storage duration in C++98 / C++03?
It seems from this answer that it isn't but it doesn't include any quotes from the standard.
Is it only safe to do that in C++11 and C++14?
回答1:
From C++14 (N3797), §27.4p2:
The objects are constructed and the associations are established at some time prior to or during the first time an object of class ios_base::Init is constructed, and in any case before the body of main begins exe- cution.295 The objects are not destroyed during program execution.296 The results of including in a translation unit shall be as if defined an instance of ios_base::Init with static storage duration. Similarly, the entire program shall behave as if there were at least one instance of ios_base::Init with static storage duration.
C++98 uses similar terminology, but without the "as if" clause.
Basically, what this forbids is using the following before main:
#include <ostream>
extern std::ostream cout;
来源：https://stackoverflow.com/questions/37706549/stdcout-usage-in-constructors-of-objects-with-static-storage-duration