On Friday 04 March 2005 1:21 pm, Calkins, Dennis wrote:

I realy don't understand How you could check this at run time since the program will NOT even LOAD to start running if you are linked agaist the NPTL and it isn't available via the LD_LIBRARY_PATH specified when you start the program.

Your program will just fail to start with an error message about not being abe to find a symbol.

Now if you specify LAZY_BINDING your program will start up, but will crash when you try to access this service. Personally I find LAZY_BINDING a pain because I don't find out until 3 hours into my program that somehting didn't load right.

I guess the real question you need to ask yourself is...

what is your program going to do if that symbol isn't available? Does your program function properly without that service? If you program can live without it why did you need it in the first place?

Typically for Dynamic checking of library services you can not use them by name in your code because of the above problems.

The best you can do is to reference them via FUNCTION POINTERS that You yourself calculate at runtime.

You open the library you want try to resolve symbols in figure out the address of that function assign it to a function pointer. If that function doesn't exist set your pointer to null.

Then in your code you specify

if ( pthread_tryjoin_np_ptr != NULL ) /* function exists */ (*pthread_tryjoin_np_ptr) (params) else ???????

But again like I said....What does your progam do on the ELSE side?

-----Original Message----- From: Jerry Feldman [mailto:gaf@blu.org] Sent: Friday, March 04, 2005 8:37 AM To: suse-programming-e@suse.com Subject: Re: [suse-programming-e] linux Threads vs. NPTL

On Friday 04 March 2005 10:51 am, Dimych wrote:

...

I had understood your point :) When saying "...that will prevent a program from linking with the Linux Threads library..." what exact errors are you getting? I though it's possible to link your programm against both those libraries at the same time.

There are some functions that exist in NPTL and not in Linux Threads. If you compile using only the Linux Threads libary (eg. /usr/lib/libpthread.so), and you code uses the function, pthread_tryjoin_np(), it will fail to link.

What I am really looking for is a way to detect at run time, if the code has been linked with the nptl library or not. -- Jerry Feldman Boston Linux and Unix user group http://www.blu.org PGP key id:C5061EA9 PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9

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More specifically, let's say that my program is going to deploy on several systems, but I want to make sure that the target system has nptl. Example, I just built a simple threaded app on a SuSE 9.2 system with a 2.6.11 kernel. Since NPLT and Linux Threads are binary compatible, a simple threaded app will work on a non-NPTL system. Your solution, above, should work. As far as the else side goes, I might just want to abort. one possible reason for doing this is that my code may be using features in nptl, such as signals where I want rely on the semantics of nptl. Or possibly I want to test my pid. On a non-nptl system, each thread has a unique PID, where on nptl each thread will have the same pid. -- Jerry Feldman Boston Linux and Unix user group http://www.blu.org PGP key id:C5061EA9 PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9