When you lie to your compiler, don’t be surprised to get results those differ from what you expect.
In this case, the coder promised his/her compiler the value of “value” won’t be changed, as it was declared const.
Therefore our best friend (yes, the compiler) who trusted the coder, thought “hey, I could cache this value in a register and not fetch it from RAM every time I reference it”, i.e. optimization.
If we change the code in the link slightly, so that function funcC would print *value before the assignment, one would see that the value of *value had actually been modified by function funcA. However, the modification was not visible in main, because the compiler was lied to as the coder explicitly told it that there would be no modification to value.
In the body of function funcC, though value was declared as a pointer to const instance, the compiler was smart enough to know it was lied to. There was a const_cast and a assignment, therefore, the modification to *value was reflected in the output.
re: 解读google C++ code style谈对C++的理解
想加入這篇 解读google C++ code style谈对C++的理解 的討論. 不幸由於不明原因, 一直被系統認為是廣告 (圖中紅字部份):
先留個底, 再看看該/能怎麼辦吧.
ps. cppblog 帳號申請中, 也許有帳號就沒這問題了吧? 不過, 看起來申請帳號要經過人工審核…
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