How exactly sc_main works !!

[ANKUR SAINI]

How "sc_main" works in SystemC ?

I mean what I understood from library is that - there is a main function defined in library which calls the sc_elab_and_sim which in turns calls the sc_main function.

But my question is SystemC library is distributed as source which user builds at his end; and links to his application.
And if SystemC has main inside it then it should have got compiled into exe! Am I right ?

Can somebody help me in understanding this flow ?

[Philipp A Hartmann]

This question in mostly about how the linker works on your platform, and not really specific to SystemC.  Let me try to give a short summary:

• Yes, the "main" symbol is needed by the final application
• For every needed symbol, the linker looks in your object files first
  • If the symbol is present there, the linker picks it up
  • If not, the linker looks in the libraries given by the user (order/lookup is platform-specific)
• Repeat this for all required symbols (including "sc_main")

So, if you define your own "main" in your application, SystemC's "main" will not be picked. This is actually a feature, as you can call "sc_elab_and_sim" manually from your "main" as well, if you want.

Hope that helps,
  Philipp

 

[ANKUR SAINI]

@Philipp A Hartmann: Thanks for the short summary. It really gave me a good understanding from the top level.

[David Black]

Just to add a bit to Philipp's excellent reply:

In part this was done to support EDA tools that support co-simulation of SystemC with other languages (e.g. SystemVerilog and VHDL). The EDA tools themselves implement main and then they can dynamically link in your sc_main as needed.

Of course if you really know how to control the linker, there are other means as well, but we don't need to go there.