为什么是/Wp64
Visual C++ 中的标志 deprecated ?
cl : Command line warning D9035 :
option 'Wp64' has been deprecated and will be removed in a future release
最佳答案
我认为/Wp64
已弃用,主要是因为针对 64 位目标进行编译将捕获它旨在捕获的错误类型(/Wp64 仅在 32 位编译中有效)。当 64 位目标出现时,该选项被添加回来,以帮助人们将他们的程序迁移到 64 位并帮助检测不是“64 位干净”的代码。
以下是 /Wp64
的各种问题的示例微软只是对修复不感兴趣 - 可能是正确的(来自 http://connect.microsoft.com/VisualStudio/feedback/details/502281/std-vector-incompatible-with-wp64-compiler-option ):
Actually, the STL isn't intentionally incompatible with
/Wp64
, nor is it completely and unconditionally incompatible with/Wp64
. The underlying problem is that/Wp64
interacts extremely badly with templates, because__w64
isn't fully integrated into the type system. Therefore, ifvector<unsigned int>
is instantiated beforevector<__w64 unsigned int>
, then both of them will behave likevector<unsigned int>
, and vice versa. On x86,SOCKET
is a typedef for__w64 unsigned int
. It's not obvious, butvector<unsigned int>
is being instantiated before yourvector<SOCKET>
, sincevector<bool>
is backed (in our implementation) byvector<unsigned int>
.Previously (in VC9 and earlier), this bad interaction between
/Wp64
and templates caused spurious warnings. In VC10, however, changes to the STL have made this worse. Now, whenvector::push_back()
is given an element of the vector itself, it figures out the element's index before doing other work. That index is obtained by subtracting the element's address from the beginning of the vector. In your repro, this involves subtractingconst SOCKET * - unsigned int *
. (The latter isunsigned int *
and notSOCKET *
due to the previously described bug.) This /should/ trigger a spurious warning, saying "I'm subtracting pointers that point to the same type on x86, but to different types on x64". However, there is a SECOND bug here, where/Wp64
gets really confused and thinks this is a hard error (while adding constness to theunsigned int *
).We agree that this bogus error message is confusing. However, since it's preceded by an un-silenceable command line deprecation warning D9035, we believe that that should be sufficient. D9035 already says that
/Wp64
shouldn't be used (although it doesn't go on to say "this option is super duper buggy, and completely unnecessary now").In the STL, we could
#error
when/Wp64
is used. However, that would break customers who are still compiling with/Wp64
(despite the deprecation warning) and aren't triggering this bogus error. The STL could also emit a warning, but the compiler is already emitting D9035.
关于visual-c++ - 为什么/Wp64 已被弃用?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/7171295/