C 运行时库版本

http://msdn.microsoft.com/en-us/library/Aa984820

The following table lists the release versions of the C run-time library files, along with their associated compiler options and environment variables. Prior to Visual C++ 4.2, the C run-time libraries contained the iostream library functions. In Visual C++ 4.2 and later, the old iostream library functions have been removed from LIBC.LIB, LIBCMT.LIB, and MSVCRT.LIB. (This change was made because the Standard C++ library has been added to Visual C++, and it contains a new set of iostream libraries. Thus, two sets of iostream functions are now included in Visual C++.) The old iostream functions now exist in their own libraries: LIBCI.LIB, LIBCIMT.LIB, and MSVCIRT.LIB. The new iostream functions, as well as many other new functions, exist in the Standard C++ libraries: LIBCP.LIB, LIBCPMT.LIB, and MSVCPRT.LIB.

When you build a release version of your project, one of the basic C run-time libraries (LIBC.LIB, LIBCMT.LIB, and MSVCRT.LIB) is linked by default, depending on the compiler option you choose (single-threaded, multithreaded, or DLL). Depending on the headers you use in your code, a library from the Standard C++ libraries or one from the old iostream libraries may also be linked:

If you include aStandard C++ library header in your code, a Standard C++ library will be linked in automatically by Visual C++ at compile time. For example:

   #include <ios>

If you include an old iostream library header, an old iostream library will be linked in automatically by Visual C++ at compile time. For example:

   #include <ios.h>

Headers determine whether a Standard C++ library, an old iostream library, or neither will be linked. Compiler options determine which of the libraries to be linked is the default (single-threaded, multithreaded, or DLL). When a specific library compiler option is defined, that library is considered to be the default and its environment variables are automatically defined.

在vc++4.1版本（包括4.1版）之前，运行库是Libc.lib, Libcmt.lib, Msvcrt.lib ，这些库包含了旧的iostream库，而这些旧的iostream库现在已经从libc.lib, libcmtlib, msvcrt.lib 中独立出来，如果链接时没有 /NODEFAULTLIB，默认链接时用 libci.lib , libcimt.lib , msvcirt.lib ，而如果指定 /NODEFAULTLIB ，则需要手动添加库。

如：

main.cpp:

#include <iostream.h>

int main()
{
    cout<<"hello"<<endl;
    return 0;
}

编译而不链接：

cl main.cpp /c

这里等同于 cl main.cpp /c /ML

/ML 为缺省状态下的运行库

其中，/c 是编译而不链接，/ML为缺省选项，对应于单线程静态版标准程序库 libc.lib

取得main.obj ，用文本打开看，里面有一行

-defaultlib:libci -defaultlib:LIBC -defaultlib:OLDNAMES

然后链接：

link main.obj /nodefaultlib libc.lib libci.lib kernel32.lib

如果调整main.cpp:

#include <iostream>
using namespace std;
int main()
{
    cout<<"hello"<<endl;
    return 0;
}

编译后再查看main.obj ，发现变成

-defaultlib:libcp -defaultlib:LIBC -defaultlib:OLDNAMES

则相应的调整链接命令行：

link main.obj /nodefaultlib libc.lib libcp.lib kernel32.lib

参考：http://blog.csdn.net/yang3yang/article/details/4360669

C Run-Time Library (without iostream)	Characteristics	Option	Defined
LIBC.LIB	Single threaded, static link	/ML
LIBCMT.LIB	Multithreaded, static link	/MT	_MT
MSVCRT.LIB	Multithreaded, dynamic link (import library for MSVCRT.DLL)	/MD	_MT, _DLL

Standard C++ Library	Characteristics	Option	Defined
LIBCP.LIB	Single threaded, static link	/ML
LIBCPMT.LIB	Multithreaded, static link	/MT	_MT
MSVCPRT.LIB	Multithreaded, dynamic link (import library for MSVCRT.DLL)	/MD	_MT, _DLL

Old Iostream Library	Characteristics	Option	Defined
LIBCI.LIB	Single threaded, static link	/ML
LIBCIMT.LIB	Multithreaded, static link	/MT	_MT
MSVCIRT.LIB	Multithreaded, dynamic link (import library for MSVCIRT.DLL)	/MD	_MT, _DLL