[OpenIndiana-discuss] SS cc multithread compilation switch (e.g., Parrot)

[James Carlson]

On 10/30/12 13:03, Udo Grabowski (IMK) wrote:
> I see sometimes people linking with -lpthread (do NOT use -pthread),
> without setting -mt for the Sun Studio compilers, see, e.g.,
> the Parrot (OI 151a7) config:
> 
> /usr/lib/parrot/3.6.0/tools/lib/Parrot/Config/Generated.pm
> 
> This is wrong and should be corrected for all OI specs for
> multithreaded programs where this switch is missing, for
> the compile and the link steps.

Both -lpthread and -lthread are unnecessary to create multithreaded
applications on modern Solaris (i.e., Solaris 10, OpenSolaris,
OpenIndiana and newer) because all of the interfaces have been folded
into libc.  All applications are multithreaded; the distinction was
removed during S10 development.

The days when there was a dummy error-returning pthread_create() in
libc, and you could tell whether you were in a single-threaded
environment by checking for that error are gone.

Any place you were using those things, you may as well stop now.  There
is a nit regarding fork1() versus forkall() semantics, but if you need
to know about that then you should definitely read the libpthread man
page.  And you should certainly use fork1() or forkall() in preference
to just plain fork() in a modern application.

The other thing "-mt" does is turn on _REENTRANT, which generally causes
the header files to give you prototypes for the slightly unusual "_r"
variants of the library functions with static data.  (They're not always
needed because most library functions defined with static data
internally use thread-local variables and are mt-safe anyway.)  But if
you're already compiling successfully without _REENTRANT, then you
probably don't need it.

A lot of blood was spilled over the multi-threaded versus
single-threaded distinction in the past, and it's a good thing that most
of the distinction is now moot.  Turn on "-mt" if you like, but I think
you may be waving a dead chicken.

-- 
James Carlson         42.703N 71.076W         <carlsonj at workingcode.com>