Subj : Re: Where to download a pthread library
To   : comp.programming.threads
From : David Butenhof
Date : Wed Mar 30 2005 12:41 pm

David Schwartz wrote:

>     The '-lpthread' flag is not a convention or standard at all.

Technically, this statement is not quite correct.

The POSIX/XCU standard specifies that with the c89 or c99 commmand, the 
formal and portable way to build a threaded program is indeed with 
exactly and only "-lpthread". Of course, on some systems that might need 
to do more than find a "libpthread.so" -- or even something entirely 
different. But that's up to the compiler/linker/driver, not the user.

ON THE OTHER HAND... hardly anyone uses the 'c89' or 'c99' commands. You 
use 'cc', or 'cxx', or 'aCC', or 'gcc'... or whatever. And in that case 
as David says your fate is in the hands of the command gods. (And 
despite what the standard says, compiler writers don't like the 
requirement to do something special for a specific "-l" value, and I'd 
be willing to bet most vendors haven't done it anyway.)

> Many 
> platforms require more than just linking in an additional library, they need 
> compiler flags (like -D_REENTRANT) as well. The standard is '-pthread' to do 
> whatever is needed for both the compiler and linker to support pthreads. 
> FreeBSD was very slow to adopt this standard due to some confusion.

-pthread is arguably a reasonably widespread CONVENTION, but definitely 
not worthy of the term "standard" either in a de jure or de facto sense. 
It'll work for many versions of gcc across platforms, (but not all), and 
several vendor compilers. The second most popular is probably "-mt" 
(e.g., on Solaris). Beyond THAT, you're entirely on your own.

-- 
Dave Butenhof, David.Butenhof@hp.com
HP Utility Pricing software, POSIX thread consultant
Manageability Solutions Lab (MSL), Hewlett-Packard Company
110 Spit Brook Road, ZK2/3-Q18, Nashua, NH 03062

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