g++ - Why do I have to pass "-pthread" option while using std::thread?
According to GCC's concurrency page, it's necessary to provide additional options to the compiler based on the features being used. You can verify that your version of GCC's threads rely on POSIX threads:
$ gcc -v 2>&1 | grep "Thread model"Thread model: posixSee this bug report for a justification for the behavior:
The problem is that not all targets need -pthread, or some which do need it spell it differently, and not all platforms define _REENTRANT when the option is used, so there's no reliable way to do what you're asking for.
pthread is an industry standard over the OS specific threads, using the OS specific calls.
std::thread is an abstraction in C++ that could be implemented using pthread or the OS's native threads. But to make it work on as many OS's as possible fast the std-library implementer could just implement it in posix as they should be good to go on all compliant OS's.
There are exceptions, some windows only std-library uses windows native threads instead.