RE: [LI] how to implement shared objects??

[Guruprasad, Mahendrakar V (IE10)]

Thanks for this information.
I feel this is kind of statistical linking of shared libraries. Is there any
way to  dynamically link them.?For example, I don't want to keep this .so
library in memoy unless I require it at particular point of time.
Before I call the functions in this .so file, can I load the .so file & when
I am done with that, can I unload this file
from memory?

Regards
Guruprasad


> -----Original Message-----
> From: SHRIDHAR N. DAITHANKAR [SMTP:[EMAIL PROTECTED]]
> Sent: Tuesday, January 11, 2000 9:34 AM
> To:   [EMAIL PROTECTED]
> Subject:      Re: [LI] how to implement shared objects??
> 
> 
> Hi
> 
>   Shared objects can actually shared libraries.
> 
> 1)How to create them?
> 
> Say you have three files a1.c,a2.c,a3.c, which you want to put in shared
> libraries.
> 
> $ gcc -c a1.c  //This will produce a1.o, object file
> $ gcc -c a2.c
> $ gcc -c a3.c
> $ ld -shared -soname mylib -o mylib.so a1.o a2.o a3.o
> 
> This will produce a library named as mylib.so. -shared flag tells linker
> to create shared onjects. -soname flag sets internal name field of the
> library. When you link the library with -lmylib, it searches this name
> field rather than the filename. As usual -o flag sets the name of the
> output file. .so is conventional extension for shared objects. Optionally
> version is also included in the name. Do a 'ls -al' in /usr/lib for
> examples.
> 
> 2)To use library.
> Say you have split the source files of your library in .h and .c format.
> You create shared library as described above. Now while writing the
> application program, include those .h file in your program. This is
> required by the compiler to find the function and variable declaration.
> Compile the file as follows.
> 
> $ gcc myapplication.c -o myapplication -lmylib
> 
> Here -l is to tell the linker to link mylib. Actually mylib is additional
> place to look for object code that matches the decleration in the code.
> 
> Typically libraries are placed in /usr/lib and /usr/local/lib. The include
> files are placed in /usr/include and /usr/local/include.
> 
> See 'man gcc' for -I and -L flags, for how to set those directories as you
> wish.
> 
> Please correct me if I am wrong.
> 
> Hope this helps.
> 
>  Bye
>   Shridhar
> 
> 
> On Tue, 11 Jan 2000, Guruprasad, Mahendrakar  V (IE10) wrote:
> 
> > 
> > 
> > >   Hi Everybody,
> > >           I heard that just like DLLs in windows , we have shared
> > > objects (.so files) concept in Linux.
> > >           Will please anybody  give me the information (how to write
> > > and all)
> > >           about the same?
> > >           I am also interested in knowing how the .so files can be
> > > loaded dynamically & if not needed should be unloaded from memory at
> run
> > > time.
> > > 
> > >   Thanks in advance
> > >    
> > >   Regards
> > >   GURUPRASAD V.M.
> 
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