11.4.1.2 Compiling and Linking With the MT-Safe libC Library

When you build an application that uses the iostream classes of the libC library to run in a multithreaded environment, compile and link the source code of the application using the -mt option. This option passes -D_REENTRANT to the preprocessor and -lthread to the linker.

Use -mt (rather than -lthread) to link with libC and libthread. This option ensures proper linking order of the libraries. Using -lthread improperly could cause your application to work incorrectly.

Single-threaded applications that use iostream classes do not require special compiler or linker options. By default, the compiler links with the libC library.