-pthread option

[ali hagigat]

Add support for multithreading using the POSIX threads library.  This
option sets flags for both the preprocessor and linker.  It does not
affect the thread safety of object code produced by the compiler or
that of libraries supplied with it.
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What is the meaning of thread safety? I wonder if anybody knows what
flags are set and please write a simple example of a multi-thread
code.