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Re: -pthread
- From: Ian Lance Taylor <iant at google dot com>
- To: Magnus Fromreide <magfr at lysator dot liu dot se>
- Cc: gcc at gcc dot gnu dot org
- Date: Tue, 04 May 2010 00:39:13 -0700
- Subject: Re: -pthread
- References: <1272949652.32287.35.camel@sara.home>
Magnus Fromreide <magfr@lysator.liu.se> writes:
> I recently ended up in a discussion about the -pthread flag at work and
> when looking at the documentation I noticed that it is defined onlt for
> SPARC and RS/6000/PowerPC.
>
> Additionally -fopenmp and -ftree-parallelize-loops say they are only
> supported on targets where -pthread are available.
>
> Now, on x86-linux it seems as if -pthread does something but there is no
> documentation of it so I'd like to know
>
> * What does -pthread do on x86?
On x86 GNU/Linux -pthread defines _REENTRANT for the preprocessor and
links against -lpthread.
> * If I am to compile a threaded program am I then requiered to use
> -pthread?
On GNU/Linux, you need to use -pthread or -D_REENTRANT at compilation
time, and you need to use -pthread or -lpthread at link time.
I agree that this really ought to be documented.
Ian