When the C runtime library is generated in the 1970s, the memory capacity of the PC is still small, and the multitasking is a novel concept, let alone how much threads. Therefore, the C runtime function library evolved at the time of the product has a serious problem in the performance of multithreaded, and cannot be used by multi-threaded programs.
Using a variety of synchronization mechanisms such as Critical Section, Mutex, Semaphore, Event, you can re-develop a set of Runtime libraries that support multi-threaded multithreaded. The problem is, plus such capabilities, may result in poor wave in size and execution efficiency - even if you only activate a thread.
The Visual C compromise is to provide two versions of the C Runtime library. A version is used to a single-threaded program, a version to multi-threaded program. The major changes in multi-threaded versions are: First, variables such as Errno now become one of each thread. Second, the data structure in the multi-line version is protected by a synchronous mechanism.
Visual C has six c runtime library products for you to choose:
◆ Single-Threaded (static) libc.lib 898, 826
◆ Multithreaded (static) libcmt.lib 951,142
◆ Multithreaded DLL MSVCRT.LIB 5,510,000
◆ Debug Single-Threaded (static) libcd.lib 2,374,542
◆ Debug Multithreaded (static) libcmtd.lib 2,949,190
◆ Debug Multithreaded DLL MSVCRTD.LIB 803, 418
The Visual C compiler provides the following options to make us decide which C Runtime library:
◆ / ml Single-Threaded (static)
◆ / MT Multithreaded (static)
◆ / MD Multithreaded DLL (Dynamic Import Library)
◆ / MLD Debug Single-Threaded (static)
◆ / MTD Debug Multithreaded (static)
◆ / MDD Debug Multithreaded DLL (Dynamic Import Library)
