Switch from -sUSE_PTHREAD to the standard -pthread. NFC

[sbc100]

We already supported this flag, but this change mostly updates all or tests and documentation to refer exclusively to that latter.

[dschuff]

🎉 this is great
(it is -pthread and not -pthreads that we recommend, right? I can never remember which of those is the "correct" one)

[sbc100]

tada this is great (it is -pthread and not -pthreads that we recommend, right? I can never remember which of those is the "correct" one)

There is no s on the end.. -pthreads with an s is just an error.

Or at least I thought it was.. looks like it is for gcc..

$ gcc -pthreads ~/test/hello.c
gcc: error: unrecognized command-line option ‘-pthreads’; did you mean ‘-pthread’?

But maybe not for clang.. thats annoying,.

$ clang -pthreads ~/test/hello.c

[sbc100]

I guess we could followup to start accepting -pthreads (plural) like clang does?

[dschuff]

Honestly I could take or leave supporting -pthreads (unless -pthreads is more common/popular). I think CMake checks for both.

[sbc100]

Honestly I could take or leave supporting -pthreads (unless -pthreads is more common/popular). I think CMake checks for both.

I did a bunch of history spelunking to try to find out why clang differs from gcc here.. but I didn't find out yet.

Got as far back as 2010: llvm/llvm-project@34d77dc

[sbc100]

Found the initial commit that added pthreads.. claims it was adding "gcc options" so I guess it was an accident of history?

llvm/llvm-project@c800391