c++ - 禁用 std::map::at()

Question

我正在用为 c++11 编写的 gcc4.7 编译一些代码，但我希望它与 gcc4.4 兼容。奇怪的是，使用的代码std::map::at()（只应该在 c++11 中定义）似乎没有给我编译错误，即使我删除了-std=c++11标志。我希望得到编译器错误，因为此代码必须与可能未使用 gcc4.7 的同事共享。这是正常的吗？有什么方法可以限制 的行为std::map吗？

Answer 1

Apparently it is not possible to achieve this with a new gcc and new libraries, at least without compiling them yourself.

As a practical solution, assuming you have a relatively modern PC (6+GB of memory, perhaps 4GB will do), I suggest you

1. Install an older Linux distro in a virtual machine, which has both the desired old gcc, and matching old standard libraries. This is far less hassle, than trying to set up an alternative compiler and library environment in your main development OS.

2. Keep your sources in version control, if you already don't.

3. Either set up a script in the old VM to check out and build the software manually, or go the extra mile, and set up a Jenkins on the VM, and create a job to poll your version control repo and do a test build automatically when you do commit on your main development environment.

Good thing about this is, you can easily set up as many different environments and OSes as you want to keep compatibility with, and still keep the main development OS up to date with latest versions.

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Original answer for the ideal world where things work right:

To get strict C++03, use these flags:

-std=c++03 -pedantic

Also, if you only want to support gcc, you may want -std=g++03 "standard" instead, but unless there is some specific feature, say C99-style VLA, which you really want to use, then I'd recommend against that. You never know what compiler you or someone else may want to use in the future.

As a side note, also recommended (at least if you want to fix the warnings too): -Wall -Wextra

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Sad reality looks like selecting the C++ standard indeed does not solve the problem. As far as I can tell, this is not really a problem in the gcc compiler, it is a problem in the GNU C++ standard library, which evidently does not check the desired C++ standard version (with #ifdefs in header files). If it bothers you, you might consider filing a bug report (if there already isn't one, though I did not find one with a quick search).