Hi can anybody throw some light on the differences between dll in vxworks and shared objects in LInux?? Also please tell me wether moduleLoad and moduleUnload do the same thing that dlopen and dlclose do in Linux..
Thanx in advance, Praveen M Nair.
Why not think about fundamentals? Conceive of a machine with two (or more) programs simultaneously loaded, each having it's own data areas, stack, etc. These can be executed by a single CPU by interrupting at suitable times and changing register contents, and give the appearance of simultaneous operation. Now arrange that machine to minimize the number of registers required to specify data areas, program areas, etc. Add a new process that never really runs, but holds binary code. That code can be called from either of the other processes as needed. It may even need some private data area, although that would not be a wise arrangement.
We can call something dlopen and use it to mount that common code in the system, to do any needed initialization, and to record where it is located in some suitable manner. We can call something moduleUnload to remove it all when done.
operating system all form one single threaded program. All else is illusion.
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Thanx.. but i have heard that dll's in VxWorks can be executables also, is it true?? if so how do i know from the code?? is it that it will contain a main similar to my executables in Linux??
-Praveen M Nair.
DLL: dynamic link library. Object file that will be opened by an application and used in order to service it.
VxWorks uses the principle of modules which are object files obtained after the compilation process.
Executable file: object file where all addresses are fixed and all missing symbols are resolved.
The other type is relocatable files: the code start address is let to 0 and the external references (eg printf()) are unresolved. The only way to execute the code is to link the relocatable file (statically or dynamically).
main is just a hook. In VxWorks, the entry point for a task is whatever the user want...
Pascal
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